Climate Science Documents
Differences and sensitivities in potential hydrologic impact of climate change to regional-scale Athabasca and Fraser River basins of the leeward and windward sides of the Canadian Rocky Mountains respectively
Sensitivities to the potential impact of Climate Change on the water resources of the Athabasca River Basin (ARB) and Fraser River Basin (FRB) were investigated. The Special Report on Emissions Scenarios (SRES) of IPCC projected by seven general circulation models (GCM), namely, Japan’s CCSRNIES, Canada’s CGCM2, Australia’s CSIROMk2b, Germany’s ECHAM4, the USA’s GFDLR30, the UK’s HadCM3, and the USA’s NCARPCM, driven under four SRES climate scenarios (A1FI, A2, B1, and B2) over three 30-year time periods (2010–2039, 2040– 2069, 2070–2100) were used in these studies. The change fields over these three 30-year time periods are assessed with respect to the 1961–1990, 30-year climate normal and based on the 1961–1990 European Community Mid-Weather Forecast (ECMWF) re-analysis data (ERA-40), which were adjusted with respect to the higher resolution GEM forecast archive of Environment Canada, and used to drive the Modified ISBA (MISBA) of Kerkhoven and Gan (Adv Water Resour 29(6):808– 826, 2006). In the ARB, the shortened snowfall season and increased sublimation together lead to a decline in the spring snowpack, and mean annual flows are expected to decline with the runoff coefficient dropping by about 8% per ◦C rise in temperature. Although the wettest scenarios predict mild increases in annual runoff in the first half of the century, all GCM and emission combinations predict large declines by the end of the twenty-first century with an average change in the annual runoff, mean maximum annual flow and mean minimum annual flow of −21%, −4.4%, and −41%, respectively. The climate scenarios in the FRB present a less clear picture of streamflows in the twenty-first century. All 18 GCM projections suggest mean annual flows in the FRB should change by ±10% with eight projections suggesting increases and 10 projecting decreases in the mean annual flow. This stark contrast with the ARB results is due to the FRB’s much milder climate. Therefore under SRES scenarios, much of the FRB is projected to become warmer than 0◦C for most of the calendar year, resulting in a decline in FRB’s characteristic snow fed annual hydrograph response, which also results in a large decline in the average maximum flow rate. Generalized equations relating mean annual runoff, mean annual minimum flows, and mean annual maximum flows to changes in rainfall, snowfall, winter temperature, and summer temperature show that flow rates in both basins are more sensitive to changes in winter than summer temperature.
Climate change effects on stream and river temperatures across the northwest U.S. from 1980–2009 and implications for salmonid fishes
Thermal regimes in rivers and streams are fundamentally important to aquatic ecosystems and are expected to change in response to climate forcing as the Earth’s temperature warms. Description and attribution of stream temperature changes are key to understanding how these ecosystems may be affected by climate change, but difficult given the rarity of long-term monitoring data. We assembled 18 temperature time-series from sites on regulated and unregulated streams in the northwest U.S. to describe historical trends from 1980–2009 and assess thermal consistency between these stream categories. Statistically significant temperature trends were detected across seven sites on unregulated streams during all seasons of the year, with a cooling trend apparent during the spring and warming trends during the summer, fall, and winter. The amount of warming more than compensated for spring cooling to cause a net temperature increase, and rates of warming were highest during the summer (raw trend = 0.17°C/decade; reconstructed trend = 0.22°C/decade). Air temperature was the dominant factor explaining long-term stream temperature trends (82–94% of trends) and inter-annual variability (48–86% of variability), except during the summer when discharge accounted for approximately half (52%) of the inter-annual variation in stream temperatures. Seasonal temperature trends at eleven sites on regulated streams were qualitatively similar to those at unregulated sites if two sites managed to reduce summer and fall temperatures were excluded from the analysis. However, these trends were never statistically significant due to greater variation among sites that resulted from local water management policies and effects of upstream reservoirs. Despite serious deficiencies in the stream temperature monitoring record, our results suggest many streams in the northwest U.S. are exhibiting a regionally coherent response to climate forcing. More extensive monitoring efforts are needed as are techniques for short-term sensitivity analysis and reconstructing historical temperature trends so that spatial and temporal patterns of warming can be better understood. Continuation of warming trends this century will increasingly stress important regional salmon and trout resources and hamper efforts to recover these species, so comprehensive vulnerability assessments are needed to provide strategic frameworks for prioritizing conservation efforts.
Global and regional trends in greenhouse gas emissions from livestock
Following IPCC guidelines (IPCC 2006), we estimate greenhouse gas emissions related to livestock in 237 countries and 11 livestock categories during the period 1961–2010. We find that in 2010 emissions of methane and nitrous oxide related to livestock worldwide represented approximately 9 % of total greenhouse gas (GHG) emissions. Global GHG emissions from livestock increased by 51 % during the analyzed period, mostly due to strong growth of emissions in developing (Non-Annex I) countries (+117 %). In contrast, developed country (Annex I) emissions decreased (−23 %). Beef and dairy cattle are the largest source of livestock emissions (74 % of global livestock emissions). Since developed countries tend to have lower CO2-equivalent GHG emissions per unit GDP and per quantity of product generated in the livestock sector, the amount of wealth generated per unit GHG emitted from the livestock sector can be increased by improving both livestock farming practices in developing countries and the overall state of economic development. Our results reveal important details of how livestock production and associated GHG emissions have occurred in time and space. Discrepancies with higher tiers, demonstrate the value of more detailed analyses, and discourage over interpretation of smaller-scale trends in the Tier 1 results, but do not undermine the value of global Tier 1 analysis.
Responses of soil and water chemistry to mountain pine beetle induced tree mortality in Grand County, Colorado, USA
Pine forest in northern Colorado and southern Wyoming, USA, are experiencing the most severe moun- tain pine beetle epidemic in recorded history, and possible degradation of drinking-water quality is a major concern. The objective of this study was to investigate possible changes in soil and water chemistry in Grand County, Colorado in response to the epidemic, and to identify major controlling influences on stream-water nutrients and C in areas affected by the mountain pine beetle. Soil moisture and soil N increased in soils beneath trees killed by the mountain pine beetle, reflecting reduced evapotranspiration and litter accumulation and decay. No significant changes in stream-water NO3 or dissolved organic C were observed; however, total N and total P increased, possibly due to litter breakdown or increased productivity related to warming air temperatures. Multiple-regression analyses indicated that % of basin affected by mountain pine beetles had minimal influence on stream-water NO3 and dissolved organic C; instead, other basin characteristics, such as percent of the basin classified as forest, were much more important.
Nutrition : The other greenhouse effect
Rising carbon dioxide levels should increase crop yields. But what if their effect on the nutritional value of our food is less benign, asks Ned Stafford.
Phytoplankton Calcification in a High-CO2 World
Ocean acidification in response to rising atmospheric CO2 partial pressures is widely expected to reduce calcification by marine organisms. From the mid-Mesozoic, coccolithophores have been major calcium carbonate producers in the world’s oceans, today accounting for about a third of the total marine CaCO3 production. Here, we present laboratory evidence that calcification and net primary production in the coccolithophore species Emiliania huxleyi are significantly increased by high CO2 partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass. Our findings show that coccolithophores are already responding and will probably continue to respond to rising atmospheric CO2 partial pressures, which has important implications for biogeochemical modeling of future oceans and climate.
Roles and Effects of Environmental Carbon Dioxide in Insect Life
Carbon dioxide (CO2) is a ubiquitous sensory cue that plays mul- tiple roles in insect behavior. In recent years understanding of the well-known role of CO2 in foraging by hematophagous insects (e.g., mosquitoes) has grown, and research on the roles of CO2 cues in the foraging and oviposition behavior of phytophagous insects and in behavior of social insects has stimulated interest in this area of insect sensory biology. This review considers those advances, as well as some of the mechanistic bases of the modulation of behavior by CO2 and important progress in our understanding of the detection and CNS processing of CO2 information in insects. Finally, this review briefly addresses how the ongoing increase in atmospheric CO2 levels may affect insect life.
What Every Conservation Biologist Should Know about Human Population
EDITORIAL:CONCLUDING PARAGRAPH: As with population issues, conservation biologists should ensure that we, as individuals and a professional society, understand the current state of knowledge about consumption and encourage constructive dialogues on consumption and its effects on biodiversity. We are not the first to highlight the issue of consumption (Baltz 1999) in this journal. Although conservation biologists may debate whether U.S. consumption is excessive (Ehrlich & Goulder 2007), the answer is more clear to some. Two months after the 2011 Society for Conservation Biology meeting mentioned above, the first author was in India attending a presentation by Elinor Os- trom (2012), who won the Nobel Prize for her work on management of the commons. At the end of the presentation, a participant asked Dr. Ostrom how we can get the world to talk about consumption as the root cause of the world’s environmental problems. This is the question conservation biologists should ask more often.
Editorial: The “New Conservation”
EDITORIAL: OPENING PARAGRAPHS A powerful but chimeric movement is rapidly gaining recognition and supporters. Christened the “new conservation,” it promotes economic development, poverty alleviation, and corporate partnerships as surrogates or substitutes for endangered species listings, protected areas, and other mainstream conservation tools. Its proponents claim that helping economically disadvantaged people to achieve a higher standard of living will kindle their sympathy and affection for nature. Because its goal is to supplant the biological diversity–based model of traditional conservation with something entirely different, namely an economic growth–based or humanitarian movement, it does not deserve to be labeled conservation.
The floodplain large-wood cycle hypothesis: A mechanism for the physical and biotic structuring of temperate forested alluvial valleys in the North Pacific coastal ecoregion
A ‘floodplain large-wood cycle’ is hypothesized as a mechanism for generating landforms and influencing river dynamics in ways that structure and maintain riparian and aquatic ecosystems of forested alluvial river valleys of the Pacific coastal temperate rainforest of North America. In the cycle, pieces of wood large enough to resist fluvial transport and remain in river channels initiate and stabilize wood jams, which in turn create alluvial patches and protect them from erosion. These stable patches provide sites for trees to ma- ture over hundreds of years in river valleys where the average cycle of floodplain turnover is much briefer, thus providing a future source of large wood and reinforcing the cycle. Different tree species can function in the floodplain large-wood cycle in different ecological regions, in different river valleys within regions, and within individual river valleys in which forest composition changes through time. The cycle promotes a physically complex, biodiverse, and self-reinforcing state. Conversely, loss of large trees from the system drives landforms and ecosystems toward an alternate stable state of diminished biogeomorphic complexity. Reestablishing large trees is thus necessary to restore such rivers. Although interactions and mechanisms may differ between biomes and in larger or smaller rivers, available evidence suggests that large riparian trees may have similarly fundamental roles in the physical and biotic structuring of river valleys elsewhere in the temperate zone. Wood debris Riparian forest Fluvial geomorphology Foundation species Biogeomorphology River restoration
Highly episodic fire and erosion regime over the past 2,000 y in the Siskiyou Mountains, Oregon
Fire is a primary mode of natural disturbance in the forests of the Pacific Northwest. Increased fuel loads following fire suppression and the occurrence of several large and severe fires have led to the perception that in many areas there is a greatly increased risk of high-severity fire compared with presettlement forests. To recon- struct the variability of the fire regime in the Siskiyou Mountains, Oregon, we analyzed a 10-m, 2,000-y sediment core for charcoal, pollen, and sedimentological data. The record reveals a highly episodic pattern of fire in which 77% of the 68 charcoal peaks before Euro-American settlement cluster within nine distinct peri- ods marked by a 15-y mean interval. The 11 largest charcoal peaks are significantly related to decadal-scale drought periods and are followed by pulses of minerogenic sediment suggestive of rapid sediment delivery. After logging in the 1950s, sediment load was increased fourfold compared with that from the most severe presettlement fire. Less severe fires, marked by smaller charcoal peaks and no sediment pulses, are not correlated significantly with drought periods. Pollen indicators of closed forests are consistent with fire-free periods of sufficient length to maintain dense forest and indicate a fire-triggered switch to more open conditions during the Medieval Climatic Anomaly. Our results indicate that over millennia fire was more episodic than revealed by nearby shorter tree-ring records and that recent severe fires have precedents during earlier drought episodes but also that sediment loads resulting from logging and road building have no precedent in earlier fire events. historical fire | climate variability | ecological resilience | logging | sediment charcoal
Forest commons and local enforcement
This article examines the relationship between local enforcement and forests used as commons. It uses a unique multicountry dataset, created over the past 15 years by the International Forestry Resources and Institutions Research Program. Drawing on original enforcement and forest commons data from 9 countries, we find that higher levels of local enforcement have a strong and positive but complex relationship to the probability of forest regeneration. This relationship holds even when the influence of a number of other factors such as user group size, subsistence, and commercial importance of forests, size of forest, and collective action for forest improvement activities is taken into account. Although several of the above factors have a statistically signifi- cant relationship to changes in the condition of forest commons, differences in levels of local enforcement strongly moderate their link with forest commons outcomes. The research, using data from diverse political, social, and ecological contexts, shows both the importance of enforcement to forest commons and some of the limits of forest governance through commons arrangements. governance sustainability collective action local institutions forest regeneration
Faustian bargains? Restoration realities in the context of biodiversity offset policies
The science and practice of ecological restoration are increasingly being called upon to compensate for the loss of biodiversity values caused by development projects. Biodiversity offsetting—compensating for losses of biodiversity at an impact site by generating ecologically equivalent gains elsewhere—therefore places substantial faith in the ability of restoration to recover lost biodiversity. Furthermore, the increase in offset-led restoration multiplies the consequences of failure to restore, since the promise of effective restoration may increase the chance that damage to biodiversity is permitted. But what evidence exists that restoration science and practice can reliably, or even feasibly, achieve the goal of ‘no net loss’ of biodiversity, and under what circumstances are successes and failures more likely? Using recent reviews of the restoration ecology literature, we examine the effectiveness of restoration as an approach for offsetting biodiversity loss, and conclude that many of the expectations set by current offset policy for ecological restoration remain unsupported by evidence. We introduce a conceptual model that illustrates three factors that limit the technical success of offsets: time lags, uncertainty and measurability of the value being offset. These factors can be managed to some extent through sound offset policy design that incorporates active adaptive management, time discounting, explicit accounting for uncertainty, and biodiversity banking. Nevertheless, the domain within which restoration can deliver ‘no net loss’ offsets remains small. A narrowing of the gap between the expectations set by offset policies and the practice of offsetting is urgently required and we urge the development of stronger links between restoration ecologists and those who make policies that are reliant upon restoration science. Keywords:Compensatory habitat - Conservation policy - Mitigation banking - Environmental risk - No net loss - Restoration success
Reliability of Indicators of Decline in Abundance
Although there are many indicators of endangerment (i.e., whether populations or species meet criteria that justify conservation action), their reliability has rarely been tested. Such indicators may fail to identify that a population or species meets criteria for conservation action (false negative) or may incorrectly show that such criteria have been met (false positive). To quantify the rate of both types of error for 20 com- monly used indicators of declining abundance (threat indicators), we used receiver operating characteristic curves derived from historical (1938–2007) data for 18 sockeye salmon (Oncorhynchus nerka) populations in the Fraser River, British Columbia, Canada. We retrospectively determined each population’s yearly status (reflected by change in abundance over time) on the basis of each indicator. We then compared that popu- lation’s status in a given year with the status in subsequent years (determined by the magnitude of decline in abundance across those years). For each sockeye population, we calculated how often each indicator of past status matched subsequent status. No single threat indicator provided error-free estimates of status, but indicators that reflected the extent (i.e., magnitude) of past decline in abundance (through comparison of current abundance with some historical baseline abundance) tended to better reflect status in subsequent years than the rate of decline over the previous 3 generations (a widely used indicator). We recommend that when possible, the reliability of various threat indicators be evaluated with empirical analyses before such indicators are used to determine the need for conservation action. These indicators should include estimates from the entire data set to take into account a historical baseline.
The payoff of conservation investments in tropical countryside
The future of biodiversity and ecosystem services hinges on har- monizing agricultural production and conservation, yet there is no planning algorithm for predicting the efficacy of conservation investments in farmland. We present a conservation planning framework for countryside (working agricultural landscapes) that calculates the production and conservation benefits to the current baseline of incremental investments. Our framework is analogous to the use of reserve design algorithms. Unlike much countryside modeling, our framework is designed for application in data- limited contexts, which are prevalent. We apply our framework to quantify the payoff for Costa Rican birds of changing farm plot and border vegetation. We show that installing windbreaks of native vegetation enhances both bird diversity and farm income, espe- cially when complementing certain crop types. We make predic- tions that differ from those of approaches currently applied to agri-environment planning,: e.g., although habitat with trees has lower local species richness than farm plot habitats (1– 44% lower), replacing any plot habitat with trees should boost regional rich- ness considerably. Our planning framework reveals the small, targeted changes on farms that can make big differences for biodiversity. biodiversity conservation planning countryside biogeography ecological-economic models matrix
THE COST OF LEAFING
Understanding the trade-offs involved for plants making leaves promises fresh insights on every scale from the plant to the planet, finds John Whitfield. Excerpt: One definition of economics is the study choice under the constraint of scarcity, and the narrowrangeofchoicesintheleafeconomics spectrum provides a vivid illus- tration of the various scarcities that dominate plants’ lives. The fact that all leaves lie fairly close to the axis of the spectrum shows that, despite the vast diversity of foliage produced over hundreds of millions of years of evolution, plants have little room for manoeuvre in how they build their leaves. “Most textbooks of ecology project the idea that there’s an almost infinite diversity of organisms,” says plant ecologist Philip Grime of the University of Sheffield, UK. “But if you look at the core biology of what organisms do with resources, you find severe constraints and trade-offs.”
Could climate change capitalism?
Economist Nicholas Stern’s latest book is a rare and masterly synthesis of climate-change science and economics. His ‘global deal’ could change capitalism for the better, says Robert Costanza.
A Changing Climate for Prediction
Standard climate model projections, which have shown the significance of global warming, must be redesigned to inform climate change adaptation and mitigation policy.
Massive Forest Dieback SW US
Summary: • Tree death is an important ecological process, but we don’t know very much about it. • MFD (Massive Forest Dieback) is often driven by stress from extreme climate events, rather than equilibrial mean climate conditions. • MFD occurs naturally in many forest types. However, there are indications that emerging patterns of dieback in some montane areas are being amplified by global climate change, and predictions of more extreme climate events suggest risk of increases in associated forest dieback episodes. • We cannot accurately predict the effects of climate change on montane forest ecosystems without better field data and model incorporation of species-specific thresholds of stress-induced tree mortality, and the dynamics of amplifying disturbances like insect outbreaks and fire. • CIRMOUNT could help address these knowledge gaps by fostering regional networks for long-term monitoring and research on: 1) plot-based demographies of multiple tree species across landscape and regional gradients to get data on pulses of mortality and natality; 2) tree growth using straightforward dendrometer band methods; 3) feedbacks between forest dieback, other disturbances, and overall ecosystem patterns and processes; and 4) effectiveness of mitigation strategies (e.g., thinning, prescribed burning).
Renewable Energy and Energy Efficiency Incentives: A Summary of Federal Programs
Summary Energy is crucial to the operation of a modern industrial and services economy. Recently, there have been growing concerns about the availability and cost of energy and about environmental impacts of fossil energy use. Those concerns have rekindled interest in energy efficiency, energy conservation, and the development and commercialization of renewable energy technologies. Many of the existing energy efficiency and renewable energy programs have authorizations tracing back to the 1970s. Many of the programs have been reauthorized and redesigned repeatedly to meet changing economic factors. The programs apply broadly to sectors ranging from industry to academia, and from state and local governments to rural communities. Since 2005, Congress has enacted several major energy laws: the Energy Policy Act of 2005 (EPACT 2005; P.L. 109-58); the Energy Independence and Security Act of 2007 (EISA; P.L. 110- 140); the Energy Improvement and Extension Act (EIEA), enacted as Division B of the Emergency Economic Stabilization Act (EESA; P.L. 110-343); and the American Reinvestment and Recovery Act (ARRA; P.L. 111-5). Each of those laws established, expanded, or modified energy efficiency and renewable energy research, development, demonstration, and deployment (RDD&D) programs. The Department of Energy (DOE) operates the greatest number of efficiency and renewable energy incentive programs. The Department of the Treasury and the Department of Agriculture (USDA) operate several programs. A few programs can also be found among the Departments of Interior (DOI), Labor (DOL), Housing and Urban Development (HUD), Veterans Affairs (VA), and the Small Business Administration (SBA). This report describes federal programs that provide grants, loans, loan guarantees, and other direct or indirect incentives for energy efficiency, energy conservation, and renewable energy. For each program, the report provides the administering agency, authorizing statute(s), annual funding, and the program expiration date. The appendixes provide summary information in a tabular format and also list recently expired programs.
Drought in the United States: Causes and Issues for Congress
Drought is a natural hazard with often significant societal, economic, and environmental consequences. Public policy issues related to drought range from how to identify and measure drought to how best to prepare for, mitigate, and respond to drought impacts, and who should bear associated costs. Severe drought in 2011 and 2012 fueled congressional interest in near-term issues, such as current (and recently expired) federal programs and their funding, and long-term issues, such as drought forecasting and various federal drought relief and mitigation actions. Continuing drought conditions throughout the country contribute to ongoing interest in federal drought policies and responses. As of April 2013, drought has persisted across approximately two-thirds of the United States and is threatening agricultural production and other sectors. More than 1,180 counties so far have been designated as disaster areas for the 2013 crop season, including 286 counties contiguous to primary drought counties. In comparison, in August 2012, more than 1,400 counties in 33 states had been designated as disaster counties by the U.S. Secretary of Agriculture. Most attention in the 112th Congress focused on the extension of expired disaster assistance programs in separate versions of a 2012 farm bill. Attention in the 113th Congress again is expected to focus on farm bill legislation; however, other bills addressing different aspects of drought policy and response have also been introduced. (For information regarding drought disaster assistance for agricultural producers, see CRS Report RS21212, Agricultural Disaster Assistance. For information on the 2012 bill, see CRS Report R42552, The 2012 Farm Bill: A Comparison of Senate-Passed S. 3240 and the House Agriculture Committee’s H.R. 6083 with Current Law.) Although agricultural losses typically dominate drought impacts, federal drought activities are not limited to agriculture. For example, the 2012 drought raised congressional interest in whether and to what extent other federal agencies have and are using authorities to address drought. Similarly, the President in August 2012 convened the White House Rural Council to assess executive branch agencies’ responses to the ongoing drought. The Administration shortly thereafter announced several new administrative actions to address the drought. While numerous federal programs address different aspects of drought, no comprehensive national drought policy exists. A 2000 National Drought Policy Commission noted the patchwork nature of drought programs, and that despite a major federal role in responding to drought, no single federal agency leads or coordinates drought programs—instead, the federal role is more of “crisis management.” Congress may opt to revisit the commission’s recommendations. Congress also may consider proposals to manage drought impacts, such as authorizing new assistance to develop or augment water supplies for localities, industries, and agriculture—or providing funding for such activities where authorities already exist. Congress also may address how the two major federal water management agencies, the U.S. Army Corps of Engineers and the Bureau of Reclamation, plan for and respond to drought. This report describes the physical causes of drought, drought history in the United States, and policy challenges related to drought. It also provides examples of recurrent regional drought conditions. For information on federal agricultural disaster assistance and related legislation, see the CRS reports noted above.
Climatic variability and episodic Pinus ponderosa establishment along the forest-grassland ecotones of Colorado
The primary objective of this study was the detection of possible climatic influences on the recent (i.e., past c. 40 years) establishment of ponderosa pine (Pinus ponderosa) at or near forest-grassland ecotones in the northern Front Range of Colorado. Germination dates were precisely determined for >500 juvenile ponderosa pine collected in six widely dispersed sample areas. All sites sampled were open areas lacking an overstory tree cover but located near seed sources. To evaluate the effects of recent climatic variation on recruitment and survival patterns, three types of climate data were used: (1) instrumental climate records from nearby local weather stations; (2) a multivariate index of El Nino/Southern Oscillation (ENSO); and (3) a regional, ponderosa pine tree-ring index sensitive to moisture variation. There is a strong association between episodic recruitment of ponderosa pine and years in which spring and fall moisture availability is high in the instrumental climate record. During the past 40 years, tree establishment was highly episodic and concentrated mainly in four years—1973, 1979, 1983, and 1990. These years are also associated with large-scale warming of sea-surface temperatures in the eastern tropical Pacific (i.e., El Nin ̃o events). These years of abundant seedling establishment also coincide with years of above average radial growth in mature ponderosa pine. Thus, at open sites suitable for the survival of shade-intolerant ponderosa pine, successful establishment of seedlings is highly episodic depending on local moisture availability related to broad-scale climatic variation. This study demonstrates the climatic sensitivity of ponderosa pine recruitment at low elevation sites along forest-grassland ecotones in the northern Colorado Front Range.
Variability, contingency and rapid change in recent subarctic alpine tree line dynamics
Summary 1 Boundaries between forest and tundra ecosystems, tree lines, are expected to advance in altitude and latitude in response to climate warming. However, varied responses to 20th century warming suggest that in addition to temperature, tree line dynamics are mediated by species-specific traits and environmental conditions at landscape and local scales. 2 We examined recent tree line dynamics at six topographically different, but climatic- ally similar, sites in south-west Yukon, Canada. Dendroecological techniques were used to reconstruct changes in density of the dominant tree species, white spruce (Picea glauca), and to construct static age distributions of willow (Salix spp.), one of two dominant shrub genera. Data were analysed to identify periods and rates of establish- ment and mortality and to relate these to past climate. 3 Tree line elevation and stand density increased significantly during the early to mid 20th century. However, this change was not uniform across sites. Spruce advanced rapidly on south-facing slopes and tree line rose 65 – 85 m in elevation. Tree line did not advance on north-facing slopes, but stand density increased 40–65%. Differences observed between aspects were due primarily to the differential presence of permafrost. Additional variability among sites was related to slope and vegetation type. Results were less conclusive for willow, but evidence for an advance was found at two sites. 4 Increases in stand density were strongly correlated with summer temperatures. The period of rapid change coincided with a 30-year period of above average temperatures, beginning in 1920. The highest correlations were obtained using a forward average of 30 – 50 years, supporting the hypothesis that tree line dynamics are controlled more by conditions influencing recruitment than by establishment alone. 5 The changes observed at several sites are suggestive of a threshold response and challenge the notion that tree lines respond gradually to climate warming. Overall, the results provide further evidence to support the idea that the pattern and timing of change is contingent on local, landscape, and regional-scale factors, as well as species’ biology. Key-words: climate change, dendroecology, ecotones, forest-tundra, non-linearity, Picea glauca, Salix glauca, stand dynamics, timberline, Yukon
Phylogenetic trees and the future of mammalian biodiversity
Phylogenies describe the origins and history of species. However, they can also help to predict species’ fates and so can be useful tools for managing the future of biodiversity. This article starts by sketching how phylogenetic, geographic, and trait information can be combined to elucidate present mammalian diversity patterns and how they arose. Recent diversification rates and standing diversity show different geographic patterns, indicating that cra- dles of diversity have moved over time. Patterns in extinction risk reflect both biological differences among mammalian lineages and differences in threat intensity among regions. Phylogenetic com- parative analyses indicate that for small-bodied mammals, extinc- tion risk is governed mostly by where the species live and the intensity of the threats, whereas for large-bodied mammals, eco- logical differences also play an important role. This modeling approach identifies species whose intrinsic biology renders them particularly vulnerable to increased human pressure. We outline how the approach might be extended to consider future trends in anthropogenic drivers, to identify likely future battlegrounds of mammalian conservation, and the likely casualties. This framework could help to highlight consequences of choosing among different future climatic and socioeconomic scenarios. We end by discussing priority-setting, showing how alternative currencies for diversity can suggest very different priorities. We argue that aiming to maximize long-term evolutionary responses is inappropriate, that conservation planning needs to consider costs as well as benefits, and that proactive conservation of largely intact systems should be part of a balanced strategy. extinction risk latent risk mammals
DOES WOOD SLOW DOWN “SLUDGE DRAGONS?” THE INTERACTION BETWEEN RIPARIAN ZONES AND DEBRIS FLOWS IN MOUNTAIN LANDSCAPES
Conservation measures for aquatic species throughout the Pacific Northwest rely heavily on maintaining forested riparian zones. A key rationale for this strategy is that the presence of standing and downed trees next to streams will provide a continuous source of wood, which is an important structural component of aquatic habitat. Yet little is known about the interactions between wood and debris flows, which are an important way that wood enters streams.Researchers from the PNW Research Station and Oregon State University created a physics-based simulation of debris flow dynamics in a headwater basin within the Oregon Coast Range. They found that the presence of wood funda- mentally changes the behavior of debris flows by reducing the momentum and distance that they travel. Because debris flow deposits are primary storage sites for sediment within headwater catchments, a shift toward shorter flows means that more sediment is stored higher up in watersheds. In addition, they found that zones with high densities of wood and sediment are relatively fixed in space and do not migrate downstream. This suggests that management strategies could specifically target achieving habitat objectives within these high accumulation zones, and there may be multiple management pathways for achieving these objectives.
Exponential Decline of Deep-Sea Ecosystem Functioning Linked to Benthic Biodiversity Loss
Here, we present a global-scale study based on 116 deep-sea sites that relates benthic biodiversity to several independent indicators of ecosystem functioning and efficiency. We show that deep-sea ecosystem functioning is exponentially related to deep-sea biodiversity and that ecosystem efficiency is also exponentially linked to functional biodiversity. These results suggest that a higher biodiversity supports higher rates of ecosystem processes and an increased efficiency with which these processes are performed. The exponential relationships presented here, being consistent across a wide range of deep-sea ecosystems, suggest that mutually positive functional interactions (ecological facilitation) can be common in the largest biome of our biosphere.Conclusions: Our results suggest that a biodiversity loss in deep-sea ecosystems might be associated with exponential reductions of their functions. Because the deep sea plays a key role in ecological and biogeochemical processes at a global scale, this study provides scientific evidence that the conservation of deep-sea biodiversity is a priority for a sustainable functioning of the worlds’ oceans.
Spatial relationship between climatologies and changes in global vegetation activity
Vegetation forms a main component of the terrestrial biosphere and plays a crucial role in land-cover and climate- related studies. Activity of vegetation systems is commonly quantified using remotely sensed vegetation indices (VI). Extensive reports on temporal trends over the past decades in time series of such indices can be found in literature. However, little remains known about the processes underlying these changes at large spatial scales. In this study, we aimed at quantifying the spatial relationship between changes in potential climatic growth constraints (i.e. temperature, precipitation and incident solar radiation) and changes in vegetation activity (1982–2008). We demonstrate an additive spatial model with 0.5° resolution, consisting of a regression component representing climate-associated effects and a spatially correlated field representing the combined influence of other factors, including land-use change. Little over 50% of the spatial variance could be attributed to changes in climatologies; conspicuously, many greening trends and browning hotspots in Argentina and Australia. The nonassociated model component may contain large- scale human interventions, feedback mechanisms or natural effects, which were not captured by the climatologies. Browning hotspots in this component were especially found in subequatorial Africa. On the scale of land-cover types, strongest relationships between climatologies and vegetation activity were found in forests, including indications for browning under warming conditions (analogous to the divergence issue discussed in dendroclimatology). Keywords: climate- and human-induced change, climatologies, Gaussian random field, growth constraints, regression, spatial additive model, vegetation-activity trends
WHY FORESTS ARE PIVOTAL IN PLANNING FOR CLIMATE CHANGE
17 slides show carbon-forest relationships including logging and carbon in US forests
Public land, timber harvests, and climate mitigation: Quantifying carbon sequestration potential on U.S. public timberlands
Scientists and policy makers have long recognized the role that forests can play in countering the atmospheric buildup of carbon dioxide (CO2), a greenhouse gas (GHG). In the United States, terrestrial carbon sequestration in private and public forests offsets approximately 11% of all GHG emissions from all sectors of the economy on an annual basis. Although much of the attention on forest carbon sequestration strategy in the United States has been on the role of private lands, public forests in the United States represent approximately 20% of the U.S. timberland area and also hold a significantly large share (30%) of the U.S. timber volume. With such a large standing timber inventory, these forested lands have considerable impact on the U.S. forest carbon balance. To help decision makers understand the carbon implications of potential changes in public timberland management, we compared a baseline timber harvest scenario with two alternative harvest scenarios and estimated annual carbon stock changes associated with each. Our analysis found that a ‘‘no timber harvest’’ scenario eliminating harvests on public lands would result in an annual increase of 17–29 million metric tonnes of carbon (MMTC) per year between 2010 and 2050—as much as a 43% increase over current sequestration levels on public timberlands and would offset up to 1.5% of total U.S. GHG emissions. In contrast, moving to a more intense harvesting policy similar to that which prevailed in the 1980s may result in annual carbon losses of 27–35 MMTC per year between 2010 and 2050. These losses would represent a significant decline (50–80%) in anticipated carbon sequestration associated with the existing timber harvest policies. If carbon sequestration were valued in the marketplace as part of a GHG offset program, the economic value of sequestered carbon on public lands could be substantial relative to timber harvest revenues. Public timberland; Forestry; Climate change; Carbon sequestration
Climate change hotspots in the United States
We use a multi-model, multi-scenario climate model ensemble to identify climate change hotspots in the continental United States. Our ensemble consists of the CMIP3 atmosphere-ocean general circulation models, along with a high-resolution nested climate modeling system. We test both high (A2) and low (B1) greenhouse gas emissions trajectories, as well as two different statistical metrics for identifying regional climate change hotspots. We find that the pattern of peak responsiveness in the CMIP3 ensemble is persistent across variations in GHG concentration, GHG trajectory, and identification method. Areas of the southwestern United States and northern Mexico are the most persistent hotspots. The high-resolution climate modeling system produces highly localized hotspots within the basic GCM structure, but with a higher sensitivity to the identification method. Across the ensemble, the pattern of relative climate change hotspots is shaped primarily by changes in interannual variability of the contributing variables rather than by changes in the long-term mean
Negative density-dependent dispersal in the American black bear (Ursus americanus) revealed by noninvasive sampling and genotyping
Although the dispersal of animals is influenced by a variety of factors, few studies have used a condition-dependent approach to assess it. The mechanisms underlying dispersal are thus poorly known in many species, especially in large mammals. We used 10 microsatellite loci to examine population density effects on sex-specific dispersal behavior in the American black bear, Ursus americanus. We tested whether dispersal increases with population density in both sexes. Fine-scale genetic struc- ture was investigated in each of four sampling areas using Mantel tests and spatial autocorrelation analyses. Our results revealed male-biased dispersal pattern in low- density areas. As population density increased, females appeared to exhibit philopa- try at smaller scales. Fine-scale genetic structure for males at higher densities may indicate reduced dispersal distances and delayed dispersal by subadults.
TOP PREDATORS AS CONSERVATION TOOLS
We review the ecological rationale behind the potential compatibility between top predators and biodiversity conservation, and examine their effectiveness as surrogate species. Evidence suggests that top predators promote species richness or are spatio-temporally associated with it for six causative or noncausative reasons: resource facilitation, trophic cascades, dependence on ecosystem productivity, sensitivity to dysfunctions, selection of heterogeneous sites and links to multiple ecosystem components. Therefore, predator-centered conservation may deliver certain biodiversity goals. To this aim, predators have been employed in conservation as keystone, umbrella, sentinel, flagship, and indicator species. However, quantitative tests of their surrogate-efficacy have been astonishingly few. Evidence suggests they may function as structuring agents and biodiversity indicators in some ecosystems but not others, and that they perform poorly as umbrella species; more consensus exists for their efficacy as sentinel and flagship species. Conservation biologists need to use apex predators more cautiously, as part of wider, context- dependent mixed strategies.
Experimental climate change weakens the insurance effect of biodiversity
Ecosystems are simultaneously affected by biodiversity loss and climate change, but we know little about how these factors interact. We predicted that climate warming and CO2-enrichment should strengthen trophic cascades by reducing the relative efficiency of predation-resistant herbivores, if herbivore consumption rate trades off with predation resistance. This weakens the insurance effect of herbivore diversity. We tested this prediction using experimental ocean warming and acidification in seagrass mesocosms. Metaanalyses of published experiments first indicated that consumption rate trades off with predation resistance. The experiment then showed that three common herbivores together controlled macroalgae and facilitated seagrass dominance, regardless of climate change. When the predation-vulnerable herbivore was excluded in normal conditions, the two resistant herbivores maintained top-down control. Under warming, however, increased algal growth outstripped control by herbivores and the system became algal-dominated. Consequently, climate change can reduce the relative efficiency of resistant herbivores and weaken the insurance effect of biodiversity.
What is the future of conservation?
In recent years, some conservation biologists and con- servation organizations have sought to refocus the field of conservation biology by de-emphasizing the goal of protecting nature for its own sake in favor of protecting the environment for its benefits to humans. This ‘new conservation science’ (NCS) has inspired debate among academics and conservationists and motivated funda- mental changes in the world’s largest conservation groups. Despite claims that NCS approaches are sup- ported by biological and social science, NCS has limited support from either. Rather, the shift in motivations and goals associated with NCS appear to arise largely from a belief system holding that the needs and wants of humans should be prioritized over any intrinsic or inherent rights and values of nature.
Conifer regeneration following stand-replacing wildfire varies along an elevation gradient in a ponderosa pine forest, Oregon, USA
Climate change is expected to increase disturbances such as stand-replacing wildfire in many ecosystems, which have the potential to drive rapid turnover in ecological communities. Ecosystem recovery, and therefore maintenance of critical structures and functions (resilience), is likely to vary across environmental gradients such as moisture availability, but has received little study. We examined conifer regeneration a decade following complete stand-replacing wildfire in dry coniferous forests spanning a 700 m elevation gradient where low elevation sites had relatively high moisture stress due to the combination of high temperature and low precipitation. Conifer regeneration varied strongly across the elevation gradient, with little tree regeneration at warm and dry low elevation sites. Logistic regression models predicted rapid increases in regeneration across the elevation gradient for both seedlings of all conifer species and ponderosa pine seedlings individually. This pattern was especially pronounced for well-established seedlings (P38 cm in height). Graminoids dominated lower elevation sites following wildfire, which may have added to moisture stress for seedlings due to competition for water. These results suggest moisture stress can be a critical factor limiting conifer regeneration following stand- replacing wildfire in dry coniferous forests, with predicted increases in temperature and drought in the coming century likely to increase the importance of moisture stress. Strongly moisture limited forested sites may fail to regenerate for extended periods after stand-replacing disturbance, suggesting these sites are high priorities for management intervention where maintaining forests is a priority.
Evolution of climate niches in European mammals?
Our ability to predict consequences of climate change is severely impaired by the lack of knowledge on the ability of species to adapt to changing environmental conditions. We used distribution data for 140 mammal species in Europe, together with data on climate, land cover and topography, to derive a statistical description of their realized climate niche. We then compared climate niche overlap of pairs of species, selected on the basis of phylogenetic information. In contrast to expectations, related species were not similar in their climate niche. Rather, even species pairs that had a common ancestor less than 1Ma already display very high climate niche distances. We interpret our finding as a strong inter- specific competitive constraint on the realized niche, rather than a rapid evolution of the fundamental niche. If correct, our results imply a very limited usefulness of climate niche models for the prediction of future mammal distributions.
Limits to adaptation
An actor-centered, risk-based approach to defining limits to social adaptation provides a useful analytic framing for identifying and anticipating these limits and informing debates over society’s responses to climate change.
Rapid evolution of flowering time by an annual plant in response to a climate fluctuation
Ongoing climate change has affected the ecological dynamics of many species and is expected to impose natural selection on ecologically important traits. Droughts and other anticipated changes in precipitation may be particularly potent selective fac- tors, especially in arid regions. Here we demonstrate the evolutionary response of an annual plant, Brassica rapa, to a recent climate fluctuation resulting in a multiyear drought. Ancestral (predrought) genotypes were recovered from stored seed and raised under a set of common environments with descendant (postdrought) genotypes and with ancestordescendant hybrids. As predicted, the abbreviated growing seasons caused by drought led to the evolution of earlier onset of flowering. Descendants bloomed earlier than ancestors, advancing first flowering by 1.9 days in one study population and 8.6 days in another. The inter- mediate flowering time of ancestordescendant hybrids supports an additive genetic basis for divergence. Experiments confirmed that summer drought selected for early flowering, that flowering time was heritable, and that selection intensities in the field were more than sufficient to account for the observed evolutionary change. Natural selection for drought escape thus appears to have caused adaptive evolution in just a few generations. A systematic effort to collect and store propagules from suitable species would provide biologists with materials to detect and elucidate the genetic basis of further evolutionary shifts driven by climate change. contemporary evolution global climate change life history theory local adaptation plant phenology
Two Modes of North American Drought from Instrumental and Paleoclimatic Data*
Droughts, which occur as a part of natural climate variability, are expected to increase in frequency and/or severity with global climate change. An improved understanding of droughts and their association with atmospheric circulation will add to the knowledge about the controls on drought, and the ways in which changes in climate may impact droughts. In this study, 1) major drought patterns across the United States have been defined, 2) the robustness of these patterns over time using tree-ring-based drought reconstructions have been evaluated, and 3) the drought patterns with respect to global atmospheric pressure patterns have been assessed. From this simple assessment, it is suggested that there are two major drought patterns across North America, which together account for about 30% of the total variance in drought patterns—one resembles the classic ENSO teleconnection, and the other displays an east–west drought dipole. The same two patterns are evident in the instrumental data and the reconstructed drought data for two different periods, 1404–2003 and 900–1350. The 500-mb circulation patterns associated with the two drought patterns suggest that the controls on drought may come from both Northern Hemisphere and tropical sources. The two drought patterns, and presumably their associated circulation patterns, vary in strength over time, indicating the combined effects of the two patterns on droughts over the past millennium.
Extreme Weather Events in Europe: preparing for climate change adaptation
This study arises from the concern that changes in weather patterns will be one of the principal effects of climate change and with these will come extreme weather. This is of considerable consequence in Europe as it impacts on the vulnerability of communities across the continent and exposes them to environmental risks. It is now widely recognised that failures in international efforts to agree on the action necessary to limit global climate change mean that adaptation to its consequences is necessary and unavoidable (Solomon et al., 2007). The changes anticipated in the occurrence and character of extreme weather events are, in many cases, the dominant factor in designing adaptation measures. Policy communities within the EU have begun to consider appropriate responses to these changes and an EU adaptation strategy is under active development and implementation. There are also sectoral EU initiatives, for example on water shortages and heat waves, and, at a regional level, on planning for floods and storms. The basic and unavoidable challenge for decision makers is to find workable and cost-effective solutions when faced with increased probabilities of very costly adverse impacts. Information about the nature and scale of these changes is essential to guide decisions on appropriate solutions. Agenda-setting for climate change and adaptation has to take place in a social or/and political setting. Scientific information about temporal changes in the probability distributions of extreme weather events over Europe, the main focus of this report, is important for informing the social and political processes that it is hoped will lead to adequate climate-change adaptation measures in Europe. This report is focused on providing a working-level assessment of the current state of the quantitative understanding of relevant extreme weather phenomena and their impacts.
Functional response of U.S. grasslands to the early 21st-century drought
Grasslands across the United States play a key role in regional livelihood and national food security. Yet, it is still unclear how this important resource will respond to the prolonged warm droughts and more intense rainfall events predicted with climate change. The early 21st-century drought in the southwestern United States resulted in hydroclimatic conditions that are similar to those expected with future climate change. We investigated the impact of the early 21st-century drought on aboveground net primary production (ANPP) of six desert and plains grasslands dominated by C4 (warm season) grasses in terms of significant deviations between observed and expected ANPP. In desert grasslands, drought-induced grass mortality led to shifts in the functional response to annual total precipitation (PT), and in some cases, new species assemblages occurred that included invasive species. In contrast, the ANPP in plains grasslands exhibited a strong linear function of the current-year PT and the previous-year ANPP, despite prolonged warm drought. We used these results to disentangle the impacts of interannual total precipitation, intra-annual precipitation patterns, and grassland abundance on ANPP, and thus generalize the functional response of C4 grasslands to predicted climate change. This will allow managers to plan for predictable shifts in resources associated with climate change related to fire risk, loss of forage, and ecosystem services. Key words: climate change; desert; extreme events; grassland production; invasive species; plains; precipitation variability; resilience; warm drought.
A dispersal-induced paradox: synchrony and stability in stochastic metapopulations
Understanding how dispersal influences the dynamics of spatially distributed populations is a major priority of both basic and applied ecologists. Two well-known effects of dispersal are spatial synchrony (positively correlated population dynamics at different points in space) and dispersal-induced stability (the phenomenon whereby populations have simpler or less extinction-prone dynamics when they are linked by dispersal than when they are isolated). Although both these effects of dispersal should occur simultaneously, they have primarily been studied separately. Herein, I summarise evidence from the literature that these effects are expected to interact, and I use a series of models to characterise that interaction. In particular, I explore the observation that although dispersal can promote both synchrony and stability singly, it is widely held that synchrony paradoxically prevents dispersal-induced stability. I show here that in many realistic scenarios, dispersal is expected to promote both synchrony and stability at once despite this apparent destabilising influence of synchrony. This work demonstrates that studying the spatial and temporal impacts of dispersal together will be vital for the conservation and management of the many communities for which human activities are altering natural dispersal rates. Keywords Autoregressive model, correlated environmental stochasticity, dispersal, dispersal-induced stability, metapopulation, negative binomial model, Ricker model, spatial heterogeneity, synchrony.
Changes in forest productivity across Alaska consistent with biome shift
Global vegetation models predict that boreal forests are particularly sensitive to a biome shift during the 21st century. This shift would manifest itself first at the biome's margins, with evergreen forest expanding into current tundra while being replaced by grasslands or temperate forest at the biome's southern edge. We evaluated changes in forest productivity since 1982 across boreal Alaska by linking satellite estimates of primary productivity and a large tree-ring data set. Trends in both records show consistent growth increases at the boreal–tundra ecotones that contrast with drought-induced productivity declines throughout interior Alaska. These patterns support the hypothesized effects of an initiating biome shift. Ultimately, tree dispersal rates, habitat availability and the rate of future climate change, and how it changes disturbance regimes, are expected to determine where the boreal biome will undergo a gradual geographic range shift, and where a more rapid decline.
The cost of policy simplification in conservation incentive programs
Incentive payments to private landowners provide a common strategy to conserve biodiversity and enhance the supply of goods and services from ecosystems. To deliver cost-effective improvements in biodiversity, payment schemes must trade-off inefficiencies that result from over-simplified policies with the administrative burden of implementing more complex incentive designs. We examine the effectiveness of different payment schemes using field parameterized, ecological economic models of extensive grazing farms. We focus on profit maximising farm management plans and use bird species as a policy-relevant indicator of biodiversity. Common policy simplifications result in a 49–100% loss in biodiversity benefits depending on the conservation target chosen. Failure to differentiate prices for conservation improvements in space is particularly problematic. Additional implementation costs that accompany more complicated policies are worth bearing even when these constitute a substantial proportion (70% or more) of the payments that would otherwise have been given to farmers. Keywords Agriculture, agri-environment scheme, biodiversity, cost-effectiveness, ecological economics, grazing, incentive
Economic growth as the limiting factor for wildlife conservation
The concept of limiting factor includes the lack of welfare factors and the presence of decimating factors. Originally applied to populations and species, the concept may also be applied to wildlife in the aggregate. Because the decimating factor of economic growth eliminates welfare factors for virtually all imperiled species via the principle of competitive exclusion, economic growth may be classified as the limiting factor for wildlife conservation. The wildlife profes- sion has been virtually silent about this limiting factor, suggesting that the pro- fession has been laboring in futility. The public, exhorted by neoclassical economists and political leaders, supports economic growth as a national goal. To address the limiting factor for wildlife conservation, wildlife professionals need to become versed in the history of economic growth theory, neoclassical economic growth theory, and the alternative growth paradigm provided by ecological economics. The Wildlife Society should lead the natural resources professions in developing a position on economic growth. carrying capacity, competitive exclusion, ecological economics, economic growth, limiting factor, neoclassical economics, niche breadth, steady state economy
Interactions and Linkages among Ecosystems during Landscape Evolution
We synthesize our findings of studies in Glacier Bay National Park and Preserve, southeastern Alaska, to elucidate interactions and linkages among terrestrial, lake, stream, and marine intertidal ecosystems as the landscape evolves following ice recession. Development in each ecosystem is initially dominated by physical processes. Over time, biotic control becomes increasingly important, although the extent of biotic control varies among ecosystems. The changes occurring in the four ecosystems are linked by landscape processes, with the nature and strength of these linkages changing through time. Change in one ecosystem has a major influence on the nature and direction of change in other ecosystems. Soil development and woody biomass accumulation on land provide an inertia that is unmatched in stream, lake, or intertidal systems. It is important that researchers and managers understand this science of change, at different spatial and temporal scales, in order to predict future states of ecological systems. The dynamics of change that we document at Glacier Bay during primary succession have important implications for managing the system with respect to anthropogenic change. Keywords: landscape, development, ecosystems, succession, linkages
Effects of tree mortality caused by a bark beetle outbreak on the ant community in the San Bernardino National Forest
Ants are used as bioindicators of the effects of disturbance on ecosystems for several reasons. First, ants are generally responsive to alteration of the biomass and diversity of the local plant community (Kalif et al., 2001) and other environmental variables (Underwood & Fisher, 2006). Second, because they occupy fixed nest locations, ants are affected by conditions on a very small scale, so that their presence and abundance are a better indicator of local conditions than are the presence or abundance of more mobile animals (Stephens & Wagner, 2006; Underwood & Fisher, 2006). Ants play important ecosystem roles and are therefore often a relevant choice for monitoring (Ho ̈lldobler & Wilson, 1990). They make up a significant percentage of the animal biomass in many ecosystems, they can be crucial to processes such as soil mixing and nutrient transport (Gentry & Stiritz, 1972), and they are important players in nutrient cycling and energy flow. Ants can also strongly influence the plant community via seed dispersal and granivory (Christian, 2001; Barrow et al., 2007). While the diversity of a given taxon is often not a reliable indicator of the diversity of other groups (Lawton et al., 1998; Bennett et al., 2009; Maleque et al., 2009; Wike et al., 2010), ant diversity is known to reflect the diversity of other invertebrates in ecosystems recovering from a disturbance in some cases (Andersen & Majer, 2004).The use of ants as bioindicators must be undertaken with caution (Underwood & Fisher, 2006). Different ant communities do not always respond to a disturbance in the same way (Arnan et al., 2009). In addition, broad measures of a bioindicator taxon, such as species richness or abundance, are potentially misleading. For instance, while it is popular to measure the species richness of bioindicator groups, the ant species richness of different habitats has been observed to respond differently to similar disturbances (Farji-Brener et al., 2002; Ratchford et al., 2005; Barrow et al., 2007), and ant species richness often does not respond at all unless disturbances are extreme (Andersen & Majer, 2004).Nonetheless, changes in the ant community can provide useful information about the responses of the ecosystem as a whole.
Impacts of climate change on the future of biodiversity
Many studies in recent years have investigated the effects of climate change on the future of biodiversity. In this review, we first examine the different possible effects of climate change that can operate at individual, population, species, community, ecosystem and biome scales, notably showing that species can respond to climate change challenges by shifting their climatic niche along three non-exclusive axes: time (e.g. phenology), space (e.g. range) and self (e.g. physiology). Then, we present the principal specificities and caveats of the most common approaches used to estimate future biodiversity at global and sub- continental scales and we synthesise their results. Finally, we highlight several challenges for future research both in theoretical and applied realms. Overall, our review shows that current estimates are very variable, depending on the method, taxonomic group, biodiversity loss metrics, spatial scales and time periods considered. Yet, the majority of models indicate alarming consequences for biodiversity, with the worst- case scenarios leading to extinction rates that would qualify as the sixth mass extinction in the history of the earth. Keywords Biodiversity, climate change, species extinctions.
Energetic and biomechanical constraints on animal migration distance
Animal migration is one of the great wonders of nature, but the factors that determine how far migrants travel remain poorly understood. We present a new quantitative model of animal migration and use it to describe the maximum migration distance of walking, swimming and flying migrants. The model combines biomechanics and metabolic scaling to show how maximum migration distance is constrained by body size for each mode of travel. The model also indicates that the number of body lengths travelled by walking and swimming migrants should be approximately invariant of body size. Data from over 200 species of migratory birds, mammals, fish, and invertebrates support the central conclusion of the model – that body size drives variation in maximum migration distance among species through its effects on metabolism and the cost of locomotion. The model provides a new tool to enhance general understanding of the ecology and evolution of migration.
Biodiversity effects on ecosystem functioning change along environmental stress gradients
Positive relationship between biodiversity and ecosystem functioning has been observed in many studies, but how this relationship is affected by environmental stress is largely unknown. To explore this influence, we measured the biomass of microalgae grown in microcosms along two stress gradients, heat and salinity, and compared our results with 13 published case studies that measured biodiversity–ecosystem functioning relationships under varying environmental conditions. We found that positive effects of biodiversity on ecosystem functioning decreased with increasing stress intensity in absolute terms. However, in relative terms, increasing stress had a stronger negative effect on low-diversity communities. This shows that more diverse biotic communities are functionally less susceptible to environmental stress, emphasises the need to maintain high levels of biodiversity as an insurance against impacts of changing environmental conditions and sets the stage for exploring the mechanisms underlying biodiversity effects in stressed ecosystems.
Maximizing return on conservation investment in the conterminous USA
Efficient conservation planning requires knowledge about conservation targets, threats to those targets, costs of conservation and the marginal return to additional conservation efforts. Systematic conservation planning typically only takes a small piece of this complex puzzle into account. Here, we use a return-on- investment (ROI) approach to prioritise lands for conservation at the county level in the conterminous USA. Our approach accounts for species richness, county area, the proportion of species’ ranges already protected, the threat of land conversion and land costs. Areas selected by a complementarity-based greedy heuristic using our full ROI approach provided greater averted species losses per dollar spent compared with areas selected by heuristics accounting for richness alone or richness and cost, and avoided acquiring lands not threatened with conversion. In contrast to traditional prioritisation approaches, our results high- light conservation bargains, opportunities to avert the threat of development and places where conservation efforts are currently lacking. Keywords Benefit cost ratio, conservation planning, economic cost, habitat protection, heuristic, land prices, reserve selection, resource allocation.
Genetic diversity in widespread species is not congruent with species richness in alpine plant communities
The Convention on Biological Diversity (CBD) aims at the conservation of all three levels of biodiversity, that is, ecosystems, species and genes. Genetic diversity represents evolutionary potential and is important for ecosystem functioning. Unfortunately, genetic diversity in natural populations is hardly considered in conservation strategies because it is difficult to measure and has been hypothesised to co-vary with species richness. This means that species richness is taken as a surrogate of genetic diversity in conservation plan- ning, though their relationship has not been properly evaluated. We tested whether the genetic and species levels of biodiversity co-vary, using a large-scale and multi-species approach. We chose the high-mountain flora of the Alps and the Carpathians as study systems and demonstrate that species richness and genetic diversity are not correlated. Species richness thus cannot act as a surrogate for genetic diversity. Our results have important consequences for implementing the CBD when designing conservation strategies. Keywords alpine vascular plants, Alps, biodiversity conservation, Carpathians, genetic diversity, species richness.
How does climate change influence demographic processes of widespread species? Lessons from the comparative analysis of contrasted populations of roe deer
How populations respond to climate change depends on the interplay between life history, resource avail- ability, and the intensity of the change. Roe deer are income breeders, with high levels of allocation to reproduction, and are hence strongly constrained by the availability of high quality resources during spring. We investigated how recent climate change has influenced demographic processes in two populations of this widespread species. Spring began increasingly earlier over the study, allowing us to identify 2 periods with contrasting onset of spring. Both populations grew more slowly when spring was early. As expected for a long-lived and iteroparous species, adult survival had the greatest potential impact on population growth. Using perturbation analyses, we measured the relative contribution of the demographic parameters to observed variation in population growth, both within and between periods and populations. Within peri- ods, the identity of the critical parameter depended on the variance in growth rate, but variation in recruit- ment was the main driver of observed demographic change between periods of contrasting spring earliness. Our results indicate that roe deer in forest habitats cannot currently cope with increasingly early springs. We hypothesise that they should shift their distribution to richer, more heterogeneous landscapes to offset energetic requirements during the critical rearing stage. Keywords Age-structured populations, demographic change, income breeding, perturbation analysis, population growth, Recruitment, Stochastic environment, Survival.
Global shifts towards positive species interactions with increasing environmental stress
The study of positive species interactions is a rapidly evolving field in ecology. Despite decades of research, controversy has emerged as to whether positive and negative interactions predictably shift with increasing environmental stress as hypothesised by the stress-gradient hypothesis (SGH). Here, we provide a synthesis of 727 tests of the SGH in plant communities across the globe to examine its generality across a variety of ecological factors. Our results show that plant interactions change with stress through an outright shift to facilitation (survival) or a reduction in competition (growth and reproduction). In a limited number of cases, plant interactions do not respond to stress, but they never shift towards competition with stress. These findings are consistent across stress types, plant growth forms, life histories, origins (invasive vs. native), climates, ecosystems and methodologies, though the magnitude of the shifts towards facilitation with stress is dependent on these factors. We suggest that future studies should employ standardised defini- tions and protocols to test the SGH, take a multi-factorial approach that considers variables such as plant traits in addition to stress, and apply the SGH to better understand how species and communities will respond to environmental change. Keywords Biotic interactions, community ecology, ecosystems and climates, environmental stress, facilitation, invasive species, meta-analysis, plant traits, the stress-gradient hypothesis.
Persistent reduced ecosystem respiration after insect disturbance in high elevation forests
Amid a worldwide increase in tree mortality, mountain pine beetles (Dendroctonus ponderosae Hopkins) have led to the death of billions of trees from Mexico to Alaska since 2000. This is predicted to have important carbon, water and energy balance feedbacks on the Earth system. Counter to current projections, we show that on a decadal scale, tree mortality causes no increase in ecosystem respiration from scales of several square metres up to an 84 km2 valley. Rather, we found comparable declines in both gross primary productivity and respiration suggesting little change in net flux, with a transitory recovery of respiration 6–7 years after mortality associated with increased incorporation of leaf litter C into soil organic matter, followed by further decline in years 8–10. The mechanism of the impact of tree mortality caused by these biotic disturbances is consistent with reduced input rather than increased output of carbon. Keywords Carbon balance, disturbance, ecosystem respiration, gross primary productivity, insect outbreak, lodgepole pine, mountain pine beetle, mountain West, subalpine forest.
Alleles underlying larval foraging behaviour influence adult dispersal in nature
The dispersal and migration of organisms have resulted in the colonisation of nearly every possible habitat and ultimately the extraordinary diversity of life. Animal dispersal tendencies are commonly heterogeneous (e.g. long vs. short) and non-random suggesting that phenotypic and genotypic variability between individuals can contribute to population-level heterogeneity in dis- persal. Using laboratory and field experiments, we demonstrate that natural allelic variation in a gene underlying a foraging polymorphism in larval fruit flies (for), also influences their dispersal tendencies as adults. Rover flies (forR; higher foraging activity) have consistently greater dispersal tendencies and are more likely to disperse longer distances than sitter flies (fors; lower foraging activity). Increasing for expression in the brain and nervous system increases dispersal in sitter flies. Our study supports the notion that variation in dispersal can be driven by intrinsic variation in food-dependent search behaviours and confirms that single gene pleiotropic effects can contrib- ute to population-level heterogeneity in dispersal.
Rapid growth in CO2 emissions after the 2008–2009 global financial crisis.pdf
1st paragraph: Global carbon dioxide emissions from fossil-fuel combustion and cement production grew 5.9% in 2010, surpassed 9 Pg of carbon (Pg C) for the first time, and more than offset the 1.4% decrease in 2009. The impact of the 2008–2009 global financial crisis (GFC) on emissions has been short-lived owing to strong emissions growth in emerging economies, a return to emissions growth in developed economies, and an increase in the fossil-fuel intensity of the world economy.
Citizen Involvement in the U.S. Endangered Species Act
Data on listed species refute critiques of citizen involvement in the U.S. Endangered Species Act.
Elevated Eocene Atmospheric CO2 and Its Subsequent Decline
Closing paragraph: Estimates of early Eocene atmospheric CO2 from Green River sodium carbonates are in the same range as those predicted by geochemical models (7). By È20 Ma, all available data (8) suggest ECO2^atm was at or near modern concentrations.
The False Spring of 2012, Earliest in North American Record
2nd paragraph: As global climate warms, increasingly warmer springs may combine with the random climatological occurrence of advective freezes, which result from cold air moving from one region to another, to dramatically increase the future risk of false springs, with profound ecological and economic consequences [e.g., Gu et al., 2008; Marino et al., 2011; Augspurger, 2013]. For example, in the false spring of 2012, an event embedded in long-term trends toward earlier spring [e.g., Schwartz et al., 2006], the frost damage to fruit trees totaled half a billion dollars in Michigan alone, prompting the federal government to declare the state a disaster area [Knudson, 2012].
The Latest on Volcanic Eruptions and Climate
2nd paragraph: It is well known that large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with a life- time of several months to about 2 years. The radiative effects of these aerosol clouds produce global cooling and are an important natural cause of climate change. Regional responses include winter warming of Northern Hemisphere continents and weakening of summer Asian and African monsoons. Even though there has not been a large eruption since the eruption of Mount Pinatubo in the Philippines on 15 June 1991, research contin- ues to produce interesting results.
EPA and the Army Corps’ Proposed Rule to Define “Waters of the United States”
Excerpt from summary : According to the agencies, the proposed rule would revise the existing regulatory definition of “waters of the United States” consistent with legal rulings—especially the Supreme Court cases—and science concerning the interconnectedness of tributaries, wetlands, and other waters to downstream waters and effects of these connections on the chemical, physical, and biological integrity of downstream waters. Waters that are “jurisdictional” are subject to the multiple regulatory requirements of the CWA: standards, discharge limitations, permits, and enforcement. Non-jurisdictional waters, in contrast, do not have the federal legal protection of those requirements. This report describes the March 25 proposed rule and includes a table comparing the existing regulatory language that defines “waters of the United States” with that in the proposal.
Bias in the attribution of forest carbon sinks
A substantial fraction of the terrestrial carbon sink, past and present, may be incorrectly attributed to environmental change rather than changes in forest management.
Sectoral contributions to surface water stress in the coterminous United States
Here, we assess current stress in the freshwater system based on the best available data in order to understand possible risks and vulnerabilities to regional water resources and the sectors dependent on freshwater. We present watershed-scale measures of surface water supply stress for the coterminous United States (US) using the water supply stress index (WaSSI) model which considers regional trends in both water supply and demand. A snapshot of contemporary annual water demand is compared against different water supply regimes, including current average supplies, current extreme-year supplies, and projected future average surface water flows under a changing climate. In addition, we investigate the contributions of different water demand sectors to current water stress. On average, water supplies are stressed, meaning that demands for water outstrip natural supplies in over 9% of the 2103 watersheds examined. These watersheds rely on reservoir storage, conveyance systems, and groundwater to meet current water demands. Overall, agriculture is the major demand-side driver of water stress in the US, whereas municipal stress is isolated to southern California. Water stress introduced by cooling water demands for power plants is punctuated across the US, indicating that a single power plant has the potential to stress water supplies at the watershed scale. On the supply side, watersheds in the western US are particularly sensitive to low flow events and projected long-term shifts in flow driven by climate change. The WaSSI results imply that not only are water resources in the southwest in particular at risk, but that there are also potential vulnerabilities to specific sectors, even in the ‘water-rich’ southeast. Keywords: water resources, surface water, water stress
Rethinking wedges
Stabilizing CO2 emissions at current levels for fifty years is not consistent with either an atmospheric CO2 concentration below 500 ppm or global temperature increases below 2 ◦C. Accepting these targets, solving the climate problem requires that emissions peak and decline in the next few decades, and ultimately fall to near zero. Phasing out emissions over 50 years could be achieved by deploying on the order of 19 ‘wedges’, each of which ramps up linearly over a period of 50 years to ultimately avoid 1 GtC y−1 of CO2 emissions. But this level of mitigation will require affordable carbon-free energy systems to be deployed at the scale of tens of terawatts. Any hope for such fundamental and disruptive transformation of the global energy system depends upon coordinated efforts to innovate, plan, and deploy new transportation and energy systems that can provide affordable energy at this scale without emitting CO2 to the atmosphere.
Linking primary production, climate and land use along an urban–wildland transect: a satellite view
Variation of green vegetation cover influences local climate dynamics, exchange of water–heat between land and atmosphere, and hydrological processes. However, the mechanism of interaction between vegetation and local climate change in subtropical areas under climate warming and anthropogenic disturbances is poorly understood. We analyzed spatial–temporal trends of vegetation with moderate-resolution imaging spectroradiometer (MODIS) vegetation index datasets over three sections, namely urban, urban–rural fringe and wildland along an urban–wildland transect in a southern mega-city area in China from 2000–2008. The results show increased photosynthetic activity occurred in the wildland and the stable urban landscape in correspondence to the rising temperature, and a considerable decrease of vegetation activity in the urban–rural fringe area, apparently due to urban expansion. On analyzing the controlling factors of climate change and human drivers of vegetation cover change, we found that temperature contributed to vegetation growth more than precipitation and that rising temperature accelerated plant physiological activity. Meanwhile, human-induced dramatic modification of land cover, e.g. conversion of natural forest and cropland to built-up areas in the urban–rural fringe, has caused significant changes of green vegetation fraction and overall primary production, which may further influence local climate. Keywords: vegetation greenness, environmental gradients, urban, transect, climate change, remote sensing, rural
Energy intensities, EROIs (energy returned on invested), and energy payback times of electricity generating power plants
The energy returned on investment, EROI, has been evaluated for typical power plants representing wind energy, photovoltaics, solar thermal, hydro, natural gas, biogas, coal and nuclear power. The strict exergy concept with no “primary energy weighting”, updated material databases, and updated technical pro- cedures make it possible to directly compare the overall efficiency of those power plants on a uniform mathematical and physical basis. Pump storage systems, needed for solar and wind energy, have been included in the EROI so that the efficiency can be compared with an “unbuffered” scenario. The results show that nuclear, hydro, coal, and natural gas power systems (in this order) are one order of magnitude more effective than photovoltaics and wind power
Increased River Alkalinization in the Eastern U.S.
The interaction between human activities and watershed geology is accelerating long-term changes in the carbon cycle of rivers. We evaluated changes in bicarbonate alkalinity, a product of chemical weathering, and tested for long-term trends at 97 sites in the eastern United States draining over 260 000 km2. We observed statistically significant increasing trends in alkalinity at 62 of the 97 sites, while remaining sites exhibited no significant decreasing trends. Over 50% of study sites also had statistically significant increasing trends in concentrations of calcium (another product of chemical weathering) where data were available. River alkalinization rates were significantly related to watershed carbonate lithology, acid deposition, and topography. These three variables explained ∼40% of variation in river alkalinization rates. The strongest predictor of river alkalinization rates was carbonate lithology. The most rapid rates of river alkalinization occurred at sites with highest inputs of acid deposition and highest elevation. The rise of alkalinity in many rivers throughout the Eastern U.S. suggests human-accelerated chemical weathering, in addition to previously documented impacts of mining and land use. Increased river alkalinization has major environmental implications including impacts on water hardness and salinization of drinking water, alterations of air−water exchange of CO2, coastal ocean acidification, and the influence of bicarbonate availability on primary production.
Sediment Trapping by Dams Creates Methane Emission Hot Spots
Inland waters transport and transform sub- stantial amounts of carbon and account for ∼18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (∼0.23 mmol CH4 m−2 d−1 vs ∼19.7 mmol CH4 m−2 d−1, respectively) and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation- driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7%.
Top 10 Places to Save for Endangered Species in a Warming World
If your house were on fire, what would you save? Would it be the precious items passed down in your family from genera- tion to generation? Or would you choose the irreplaceable photos that would disappear forever? Where do you even start? What if it wasn’t just your house, but your whole planet that was on fire?That is the scenario we face today. Climate change has arrived. No longer clouds gathering in the distance, the storm is here now—melting our titanic glaciers, drying our mighty rivers and setting our deserts ablaze. What do we save? For the Endangered Species Coalition, the answer is easy: we start with our endangered species. They are already on the brink of extinction, so vulnerable that a stressor such as climate change acts as a bulldozer, steaming full force ahead with the potential to shove them right over the edge of extinction.And where do we begin? We asked our member groups and our scientists, “If we want to save endangered species from climate change, what habitats do we need to protect?” Together, they identified ten ecosystems that are critical to conserve if we are to protect our nation’s endangered species from the ravages of climate change.
Impacts of the EU biofuel policy on agricultural markets and land use
The European Union's Renewable Energy Directive (RED)1 sets an overall target of 20% of the EU's energy used to come from renewable sources by 2020. As part of this target, at least 10% of total transport fuel consumption is to come from renewable energies (RE). In parallel, the Fuel Quality Directive (FQD)2 requires fuel suppliers to reduce the carbon intensity of road fuels they supply by 6% in 2020. The EU Member States were required to report their expectations and plans on how to meet these targets in National Renewable Energy Action Plans (NREAP) by 30 June 2010, including the technology mix and the trajectory to reach them. However, in the end the extent to which the 2020 mandate will be met is uncertain. During the 2012 Workshop on 'Commodity Market Development in Europe – Outlook'3, held in Brussels, many participants highlighted the difficulty to reach such a level of biofuel consumption. In addition, according to the 2012 ECOFYS report on renewable energy progress and biofuels' sustainability, in 2012 the objectives for transport were already not being met. The European car industry is indeed not ready to use blends with high shares of biodiesel and ethanol. Moreover the contribution of second-generation biofuels towards meeting the target is expected to remain small. Furthermore the repeated droughts in recent years have put pressure on food prices and put forward the world food security debate. The use of food crops to produce biofuels instead of feeding the world has been criticised. Sustainability of biodiesel is especially questioned. In order to reduce the indirect land use change (ILUC) which may be caused by higher demand for food and feed crops for biofuel, on 17 October 2012 the European Commission (EC) published a proposal to amend the RED (COM(2012)595). It proposed to cap the amount of first-generation biofuels that can count towards the 10% renewable energy target at 5%4. In addition, the use of advanced biofuels, with no or low ILUC emissions, would be promoted by weighting their contribution towards fulfilling the target more favourably. The estimated ILUC emissions are also included in the greenhouse gas balance of biofuels for the purpose of compliance with the reporting obligations under the RED and FQD. Therefore the development of the biofuel market is highly uncertain, especially in the European Union (EU). This report aims to analyse different scenarios that could occur in the EU in the years to come.
PHENOLOGY OF MIXED WOODY–HERBACEOUS ECOSYSTEMS FOLLOWING EXTREME EVENTS: NET AND DIFFERENTIAL RESPONSES
We present responses of a mixed woody–herbaceous ecosystem type to an extreme event: regional-scale pinon pine mortality following an extended drought and the subsequent herbaceous green-up following the first wet period after the drought. This example highlights how reductions in greenness of the slower, more stable evergreen woody component can rapidly be offset by increases associated with resources made available to the relatively more responsive herbaceous component. We hypothesize that such two-phase phenological responses to extreme events are characteristic of many mixed woody– herbaceous ecosystems. Key words: die-off; disturbance; drought; extreme events; fire; Mesita del Buey; mortality; normalized difference vegetation index; phenology; pin ̃on; semiarid woodlands; woody and herbaceous plants.
Long-term aspen cover change in the western US
Quaking aspen (Populus tremuloides Michx.) is one of the most important tree species in the western United States due to its role in biodiversity, tourism, and other ecological and aesthetic values. This paper provides an overview of the drivers of long-term aspen cover change in the western US and how these drivers operate on diverse spatial and temporal scales. There has been substantial concern that aspen has been declining in the western US, but trends of aspen persistence vary both geographically and tem- porally. One important goal for future research is to better understand long-term and broad-scale changes in aspen cover across its range. Inferences about aspen dynamics are contingent on the spatial and temporal scales of inquiry, thus differences in scope and design among studies partly explain varia- tion among conclusions. For example, major aspen decline has been noted when the spatial scale of inquiry is relatively small and the temporal scale of inquiry is relatively short. Thus, it is important to consider the scale of research when addressing aspen dynamics. Successional replacement of aspen by conifer species is most pronounced in systems shaped by long fire intervals and can thus be seen as part of a normal, long-term fluctuation in forest composition. Aspen decline was initially reported primarily at the margins of aspen’s distribution, but may be becoming more ubiquitous due to the direct effects of climate (e.g. drought). In contrast, the indirect effects of recent climate (e.g. forest fires, bark beetle outbreaks, and compounded disturbances) appear to favor aspen and may facilitate expansion of this forest type. Thus, future aspen trends are likely to depend on the net result of the direct and indirect effects of altered climate.
Four-year response of underplanted American chestnut (Castanea dentata) and three competitors to midstory removal, root trenching, and weeding treatments in an oak-hickory forest
American chestnut (Castanea dentata) has been killed or reduced to recurrent stump sprouts throughout its range following the importation of multiple pathogens in the 19th and early 20th centuries. Under- standing what drives chestnut growth and survival would aid the development of appropriate silvicultural guidelines for restoring the species once blight resistant stock is available. Here we compare the response of planted American and hybrid chestnut seedlings to that of important competitors, northern red oak (Quercus rubra), sugar maple (Acer saccharum) and red maple (A. rubrum), under treatments designed to evaluate the effects of various sources of competition on seedling growth and survival. After four years, American and hybrid chestnut was significantly taller in trenched plots (181.8 ± 12.4 cm; mean ± SE) compared to untrenched plots (127.5 ± 7.9 cm), weeded plots (174.5 ± 12.7 cm) compared to unweeded plots (130.1 ± 6.5 cm) and in midstory removal plots (156.6 ± 7.8) versus full canopy (88.8 ± 11.7 cm), and had outperformed the other species in most competitive environments. Chestnut was the only species to respond to every treatment with significant growth increases, displaying a nota- ble ability to capture growing space when it became available. We suggest that American chestnut res- toration may be more successful where early stand management provides chestnut a brief period of reduced competition. Specifically, midstory removal can increase survival and growth of underplanted American chestnut, and when combined with multi-stage shelterwood removals of the overstory and some amount of competition control, may constitute a viable restoration strategy for chestnut in many of the eastern oak-hickory forests where it was originally dominant.
Feedbacks of Terrestrial Ecosystems to Climate Change
Most modeling studies on terrestrial feedbacks to warming over the twenty-first century imply that the net feedbacks are negative—that changes in ecosystems, on the whole, resist warming, largely through ecosystem carbon storage. Although it is clear that potentially important mechanisms can lead to carbon storage, a number of less well- understood mechanisms, several of which are rarely or incompletely modeled, tend to diminish the negative feedbacks or lead to positive feedbacks. At high latitudes, negative feedbacks from forest expansion are likely to be largely or completely compensated by positive feedbacks from decreased albedo, increased carbon emissions from thawed permafrost, and increased wildfire. At low latitudes, negative feedbacks to warming will be decreased or eliminated, largely through direct human impacts. With modest warming, net feedbacks of terrestrial ecosystems to warming are likely to be negative in the tropics and positive at high latitudes. Larger amounts of warming will generally push the feedbacks toward the positive.
Wildfire responses to abrupt climate change in North America
It is widely accepted, based on data from the last few decades and on model simulations, that anthropogenic climate change will cause increased fire activity. However, less attention has been paid to the relationship between abrupt climate changes and heightened fire activity in the paleorecord. We use 35 charcoal and pollen records to assess how fire regimes in North America changed during the last glacial–interglacial transition (15 to 10 ka), a time of large and rapid climate changes. We also test the hypothesis that a comet impact initiated continental-scale wildfires at 12.9 ka; the data do not support this idea, nor are continent-wide fires indi- cated at any time during deglaciation. There are, however, clear links between large climate changes and fire activity. Biomass burning gradually increased from the glacial period to the begin- ning of the Younger Dryas. Although there are changes in biomass burning during the Younger Dryas, there is no systematic trend. There is a further increase in biomass burning after the Younger Dryas. Intervals of rapid climate change at 13.9, 13.2, and 11.7 ka are marked by large increases in fire activity. The timing of changes in fire is not coincident with changes in human population density or the timing of the extinction of the megafauna. Although these factors could have contributed to fire-regime changes at individual sites or at specific times, the charcoal data indicate an important role for climate, and particularly rapid climate change, in deter- mining broad-scale levels of fire activity. biomass burning charcoal comet Younger Dryas
Linking forest fires to lake metabolism and carbon dioxide emissions in the boreal region of Northern Quebec
Natural fires annually decimate up to 1% of the forested area in the boreal region of Que ́bec, and represent a major structuring force in the region, creating a mosaic of watersheds characterized by large variations in vegetation structure and composition. Here, we investigate the possible connections between this fire-induced watershed heterogeneity and lake metabolism and CO2 dynamics. Plankton respiration, and water–air CO2 fluxes were measured in the epilimnia of 50 lakes, selected to lie within distinct watershed types in terms of postfire terrestrial succession in the boreal region of Northern Que ́ bec. Plankton respiration varied widely among lakes (from 21 to 211lgCL1day1), was negatively related to lake area, and positively related to dis- solved organic carbon (DOC). All lakes were supersaturated in CO2 and the resulting carbon (C) flux to the atmosphere (150 to over 3000 mg C m2 day1) was negatively related to lake area and positively to DOC concentration. CO2 fluxes were positively related to integrated water column respiration, suggesting a biological component in this flux. Both respiration and CO2 fluxes were strongly negatively related to years after the last fire in the basin, such that lakes in recently burnt basins had significantly higher C emissions, even after the influence of lake size was removed. No significant differences were found in nutrients, chlorophyll, and DOC between lakes in different basin types, suggesting that the fire-induced watershed features influence other, more subtle aspects, such as the quality of the organic C reaching lakes. The fire-induced enhancement of lake organic C mineralization and C emissions represents a long-term impact that increases the overall C loss from the landscape as the result of fire, but which has never been included in current regional C budgets and future projections. The need to account for this additional fire-induced C loss becomes critical in the face of predictions of increasing incidence of fire in the circumboreal landscape. Keywords: boreal, carbon dioxide flux, climate, forest fire, lakes, organic carbon, plankton respiration,
The Relative Impact of Harvest and Fire upon Landscape-Level Dynamics of Older Forests: Lessons from the Northwest Forest Plan
Interest in preserving older forests at the landscape level has increased in many regions, including the Pacific Northwest of the United States. The North- west Forest Plan (NWFP) of 1994 initiated a sig- nificant reduction in the harvesting of older forests on federal land. We used historical satellite imagery to assess the effect of this reduction in relation to: past harvest rates, management of non-federal forests, and the growing role of fire. Harvest rates in non-federal large-diameter forests (LDF) either decreased or remained stable at relatively high rates following the NWFP, meaning that harvest reductions on federal forests, which cover half of the region, resulted in a significant regional drop in the loss of LDF to harvest. However, increased losses of LDF to fire outweighed reductions in LDF harvest across large areas of the region. Elevated fire levels in the western United States have been correlated to changing climatic conditions, and if recent fire patterns persist, preservation of older forests in dry ecosystems will depend upon practical and coordi- nated fire management across the landscape. Key words: disturbance; fire; landsat; forest management; Northwest Forest Plan; old growth.
Cumulative Effects of Fire and Fuels Management on Stream Water Quality and Ecosystem Dynamics
Prescribed fires and wildland fire-use are increasingly important management tools used to reduce fuel loads and restore the ecological integrity of western forests. Although a basic understanding of the effects of fire on aquatic ecosystems exists, the cumulative and possibly synergistic effects of wildfire following prescribed fire are unknown. Wildfires following prescribed fire may produce different burn severities and effects on riparian and stream ecosystems than wildfires in fire suppressed forests (e.g., fires absent >70 yrs) or prescribed fires alone. The goal of this study was to quantify and compare the effects of wildfire on stream and riparian ecosystems under three fire management practices: (1) wildfire following prescribed fire, (2) wildfire in fire suppressed forests, and (3) wildfire occurring at historic fire return intervals. We compared 6-7 years (2001-2006/07) of stream and riparian data collected prior to two large wildfire events to 3 years (2008-2010) of similar data collected after wildfire in catchments along the South Fork Salmon River and Big Creek in central Idaho. Here we report our preliminary findings on riparian- and catchment-level burn severity patterns, riparian forest structure, hydrology, amphibians, aquatic macroinvertebrates, periphyton, and instream habitat, including temperature, chemistry, substrate, sedimentation, and large woody debris. We found that the management practice of prescribed fire treatment prior to wildfire significantly reduced wildfire burn severity patterns in treated catchments relative to untreated catchments. This reduction in burn severity appeared to reduce wildfire effects on stream and riparian ecosystems rather than cause cumulative effects of prescribed fire plus wildfire. Instead, we found that the effects of natural inter-annual variability in stream flow and stochastic disturbances, such as debris flows and channel scouring events, are the dominant drivers of change in stream and riparian habitats in this region, with fire management practices playing a much smaller role.
Relationships of Fire and Precipitation Regimes in Temperate Forests of the Eastern United States
Fire affects virtually all terrestrial ecosystems but occurs more commonly in some than in others. This paper investigates how climate, specifically the moisture regime, influences the flammability of different landscapes in the eastern United States. A previous study of spatial differ- ences in fire regimes across the central Appalachian Mountains suggested that intra-annual precipitation variability influences fire occurrence more strongly than does total annual precipitation. The results presented here support that conclusion. The relationship of fire occurrence to moisture regime is also considered for the entire eastern United States. To do so, mean annual wildfire density and mean annual area burned were calculated for 34 national forests and parks representing the major vegetation and climatic conditions throughout the eastern forests. The relationship between fire activity and two climate variables was analyzed: mean annual moisture balance [precipitation P 2 potential evapotranspiration (PET)] and daily precipitation variability (coefficient of variability for daily precipitation). Fire activity is related to both climate variables but displays a stronger relationship with precipitation vari- ability. The southeastern United States is particularly noteworthy for its high wildfire activity, which is associated with a warm, humid climate and a variable precipitation regime, which promote heavy fuel production and rapid drying of fuels. KEYWORDS: Wildfire; Fire climatology; Precipitation variability; Climatic variability
Climate change and disruptions to global fire activity
Future disruptions to fire activity will threaten ecosystems and human well-being throughout the world, yet there are few fire projections at global scales and almost none from a broad range of global climate models (GCMs). Here we integrate global fire datasets and environmental covariates to build spatial statistical models of fire probability at a 0.58 resolution and examine environmental controls on fire activity. Fire models are driven by climate norms from 16 GCMs (A2 emissions scenario) to assess the magnitude and direction of change over two time periods, 2010–2039 and 2070–2099. From the ensemble results, we identify areas of consensus for increases or decreases in fire activity, as well as areas where GCMs disagree. Although certain biomes are sensitive to constraints on biomass productivity and others to atmospheric conditions promoting combustion, substantial and rapid shifts are projected for future fire activity across vast portions of the globe. In the near term, the most consistent increases in fire activity occur in biomes with already somewhat warm climates; decreases are less pronounced and concentrated primarily in a few tropical and subtropical biomes. However, models do not agree on the direction of near- term changes across more than 50% of terrestrial lands, highlighting major uncertainties in the next few decades. By the end of the century, the magnitude and the agreement in direction of change are projected to increase substantially. Most far-term model agreement on increasing fire probabilities (;62%) occurs at mid- to high-latitudes, while agreement on decreasing probabilities (;20%) is mainly in the tropics. Although our global models demonstrate that long-term environmental norms are very successful at capturing chronic fire probability patterns, future work is necessary to assess how much more explanatory power would be added through interannual variation in climate variables. This study provides a first examination of global disruptions to fire activity using an empirically based statistical framework and a multi-model ensemble of GCM projections, an important step toward assessing fire-related vulnerabilities to humans and the ecosystems upon which they depend. Key words: climatic constraints; ensemble model uncertainty; flammability; global climate models (GCM); GCM agreement; global fire probabilities; resources to burn; spatial statistical models; species distribution models.
Managing Wildfire Risk in Fire-Prone Landscapes: How Are Private Landowners Contributing?
The fire-prone landscapes include both public and private lands. Wildfire burns indiscriminately across property boundaries, which means that the way potential fuels are managed on one piece of property can affect wildfire risk on neighboring lands. KeY FINdINGS • Private forest landowners who perceive great fire risk or are concerned about hazardous fuel conditions on nearby public lands are more likely to reduce fuels on their properties and cooperate with public agencies on fuel reduction. • Most private landowners surveyed reduce fuel independently, rather than in cooperation with others, primarily because of distrust and social norms about private property ownership. • Forest owners who live on a forested parcel of land are much more likely to reduce fuels on that parcel than are owners who maintain residences elsewhere. • Limited opportunity to offset the costs of fuel reduction (e.g., with public incentive programs or income from markets for logs and wood products) poses greater constraints to fuel reduction by private forest owners than does lack of knowledge or skills.
Characterizing Fire-on-Fire interactions in three Large Wilderness areas
The interaction of fires, where one fire burns into another recently burned area, is receiving increased attention from scientists and land managers wishing to describe the role of fire scars in affecting landscape pattern and future fire spread. Here, we quantify fire-on- fire interactions in terms of frequency, size, and time-since-previous fire (TSPF) in three large wilderness areas in Montana and Idaho, USA, from 1984 to present, using spatially consistent large fire perimeter data from the Monitoring Trends in Burn Severity (MTBS) dataset. The analysis is supplemented with less consistent fire perimeter data from a re- gional fire atlas in order to examine the potential role played by smaller fires in fire-on-fire interactions. We compare current rates of burning to existing estimates using the natural fire rotation (NFR) to determine whether recent fire activity falls within established historical ranges. We also compare actual fires to randomly located fires to establish whether the frequency and size of re-burns differ by chance. Finally, we systematically classify shared fire edges as fire-stopping or breached to quantify the effect of previous fires on subsequent fire spread. In total, more than half of the Frank Church, one-quarter of the Bob Marshall, and fifteen percent of the Selway-Bitterroot wilderness areas have burned since 1984. Area burned within each of the study areas yielded NFRs that are consistent with results derived from fire atlas and tree-ring research studies. The data show that re- burning occurs less frequently than chance in the Frank Church Wilderness Area, perhaps less frequently in the Bob Marshall Wilderness Area, and the same as chance in the Selway-Bitterroot Wilderness Area. In each of the study areas, the total amount of edge at which a fire met another fire was less than three percent of the total available perimeter. However, ~80% of the total edge encountered was breached, resulting in fire spreading onto previously burned landscapes and re-burning at least 40 ha. Year-to-year variability in re-burn occurrence was high, and the size of re-burns was typically small, implying a general resistance to re-burning, but the preponderance of small patches resulting from fire interactions has perhaps significant ecological implications. There was a systematic decrease in the frequency of small to medium sized re-burns (40 ha to 405 ha) as time be- tween fires increased in all three wilderness areas. The frequency of large re-burns in- creased with time in the Frank Church wilderness area, but this trend was not apparent in the other two wilderness areas. Overall, fire-on-fire interactions show a high degree of complexity, making direct comparisons between the three wilderness areas difficult, but the evidence suggests that large wildfires generally inhibit the spread of subsequent fires, while small fires appear to have little impact on the spread of other fires.
Robust spatially aggregated projections of climate extremes
Many climatic extremes are changing1–5, and decision-makers express a strong need for reliable information on further changes over the coming decades as a basis for adaptation strategies. Here, we demonstrate that for extremes stakeholders will have to deal with large irreducible uncertainties on local to regional scales as a result of internal variability, even if climate models improve rapidly. A multimember initial condition ensemble carried out with an Earth system model shows that trends towards more intense hot and less intense cold extremes may be masked or even reversed locally for the coming three to five decades even if greenhouse gas emissions rapidly increase. Likewise, despite a long-term trend towards more intense precipitation and longer dry spells, multidecadal trends of op- posite sign cannot be excluded over many land points. However, extremes may dramatically change at a rate much larger than anticipated from the long-term signal. Despite these large irreducible uncertainties on the local scale, projections are remarkably consistent from an aggregated spatial probability perspective. Models agree that within only three decades about half of the land fraction will see significantly more intense hot extremes. We show that even in the short term the land fraction experiencing more intense precipitation events is larger than expected from internal variability. The proposed perspective yields valuable information for decision-makers and stakeholders at the international level.
Five Stages of Climate Grief
University of Montana Professor, climate scientist, and Nobel Peace Prize winner Steve W. Running has written about "The 5 Stages of Climate Grief." Modeled after Elisabeth Kubler- Ross's Five Stages of Grief model, Running's essay focuses on understanding each stage to move to the final stage of acceptance more easily. Running explains how people must accept global warming as a problem before they resolve to do something about it.
Does global warming favour the occurrence of extreme floods in European Alps? First evidences from a NW Alps proglacial lake sediment record
Our record suggests climate warming is favouring the occurrence of high magnitude torrential flood events in high-altitude catchments.
Food-Miles and the Relative Climate Impacts of Food Choices in the United States
Despite significant recent public concern and media attention to the environmental impacts of food, few studies in the United States have systematically compared the life-cycle greenhouse gas (GHG) emissions associated with food production against long-distance distribution, aka “food-miles.” We find that although food is transported long distances in general (1640 km delivery and 6760 km life-cycle supply chain on average) the GHG emissions associated with food are dominated by the production phase, contributing 83% of the average U.S. household’s 8.1 t CO2e/yr footprint for food consumption. Transportation as a whole represents only 11% of life-cycle GHG emissions, and final delivery from producer to retail contributes only 4%. Different food groups exhibit a large range in GHG-intensity; on average, red meat is around 150% more GHG- intensive than chicken or fish. Thus, we suggest that dietary shift can be a more effective means of lowering an average household’s food-related climate footprint than “buying local.” Shifting less than one day per week’s worth of calories from red meat and dairy products to chicken, fish, eggs, or a vegetable-based diet achieves more GHG reduction than buying all locally sourced food.
The Impact of Boreal Forest Fire on Climate Warming
We report measurements and analysis of a boreal forest fire, integrating the effects of greenhouse gases, aerosols, black carbon deposition on snow and sea ice, and postfire changes in surface albedo. The net effect of all agents was to increase radiative forcing during the first year (34 ± 31 Watts per square meter of burned area), but to decrease radiative forcing when averaged over an 80-year fire cycle (−2.3 ± 2.2 Watts per square meter) because multidecadal increases in surface albedo had a larger impact than fire-emitted greenhouse gases. This result implies that future increases in boreal fire may not accelerate climate warming.
Ancient Biomolecules from Deep Ice Cores Reveal a Forested Southern Greenland
It is difficult to obtain fossil data from the 10% of Earth’s terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections.
The potential transient dynamics of forests in New England under historical and projected future climate change
Projections of vegetation distribution that incorporate the transient responses of vegetation to climate change are likely to be more efficacious than those that assume an equilibrium between climate and vegetation. We examine the non-equilibrium dynamics of a temperate forest region under historic and projected future climate change using the dynamic ecosystem model LPJ-GUESS. We parameterized LPJ-GUESS for the New England region of the United Sates utilizing eight forest cover types that comprise the regionally dominant species. We developed a set of climate data at a monthly-step and a 30-arc second spatial resolution to run the model. These datasets consist of past climate observations for the period 1901–2006 and three general circulation model projections for the period 2007–2099. Our baseline (1971–2000) simulation reproduces the distribution of forest types in our study region as compared to the National Land Cover Data 2001 (Kappa statistic00.54). Under historic and nine future climate change scenarios, maple-beech-basswood, oaks and aspen- birch were modeled to move upslope at an estimated rate of 0.2, 0.3 and 0.5 myr−1 from 1901 to 2006, and continued this trend at an accelerated rate of around 0.5, 0.9 and 1.7 myr−1 from 2007 to 2099. Spruce-fir and white pine-cedar were modeled to contract to mountain ranges and cooler regions of our study region under projected future climate change scenarios. By the end of the 21st century, 60% of New England is projected to be dominated by oaks relative to 21% at the beginning of the 21st century, while northern New England is modeled to be dominated by aspen-birch. In mid and central New England, maple-beech-basswood, yellow birch-elm and hickories co-occur and form novel species associations. In addition to warming-induced northward and upslope shifts, climate change causes more complex changes in our simulations, such as reversed conversions between forest types that currently share similar bioclimatic ranges. These results underline the importance of considering community interactions and transient dynamics in modeling studies of climate change impacts on forest ecosystems.
The Importance of Land-Use Legacies to Ecology and Conservation
Recognition of the importance of land-use history and its legacies in most ecological systems has been a major factor driving the recent focus on human activity as a legitimate and essential subject of environmental science. Ecologists, conservationists, and natural resource policymakers now recognize that the legacies of land-use activities continue to influence ecosystem structure and function for decades or centuries—or even longer— after those activities have ceased. Consequently, recognition of these historical legacies adds explanatory power to our understanding of modern conditions at scales from organisms to the globe and reduces missteps in anticipating or managing for future conditions. As a result, environmental history emerges as an integral part of ecological science and conservation planning. By considering diverse ecological phenomena, ranging from biodiversity and biogeochemical cycles to ecosystem resilience to anthropogenic stress, and by examining terrestrial and aquatic ecosystems in temperate to tropical biomes, this article demonstrates the ubiquity and importance of land-use legacies to environmental science and management. Keywords: land use, disturbance, conservation, ecosystem process, natural resource management
Conservation Biology: Predicting Birds’ Responses to Forest Fragmentation
Understanding species’ ecological responses to habitat fragmentation is critical for biodiversity conservation, especially in tropical forests. A detailed recent study has shown that changes in the abundances of bird species following fragmentation may be dramatic and unpredictable.
The subnivium: a deteriorating seasonal refugium
For many terrestrial organisms in the Northern Hemisphere, winter is a period of resource scarcity and energy deficits, survivable only because a seasonal refugium – the “subnivium” – exists beneath the snow. The warmer and more stable conditions within the subnivium are principally driven by snow duration, density, and depth. In temperate regions, the subnivium is important for the overwintering success of plants and animals, yet winter conditions are changing rapidly worldwide. Throughout the Northern Hemisphere, the impacts of climate change are predicted to be most prominent during the winter months, resulting in a shorter snow season and decreased snow depth. These climatic changes will likely modify the defining qualities of the subnivium, resulting in broad-scale shifts in distributions of species that are dependent on these refugia. Resultant changes to the subnivium, however, will be spatially and temporally variable. We believe that ecologists and managers are overlooking this widespread, crucial, and vulnerable seasonal refugium, which is rapidly deteriorating due to global climate change.
Effects of Climatic Variability and Change on Forest Ecosystems: General Technical Report PNW-GTR-870 December 2012
This report is a scientific assessment of the current condition and likely future condition of forest resources in the United States relative to climatic variability and change. It serves as the U.S. Forest Service forest sector technical report for the National Climate Assessment and includes descriptions of key regional issues and examples of a risk-based framework for assessing climate-change effects. By the end of the 21st century, forest ecosystems in the United States will differ from those of today as a result of changing climate. Although increases in temperature, changes in precipitation, higher atmospheric concentrations of carbon dioxide (CO2), and higher nitrogen (N) deposition may change ecosystem structure and function, the most rapidly visible and most significant short-term effects on forest ecosystems will be caused by altered disturbance regimes. For example, wildfires, insect infestations, pulses of erosion and flooding, and drought-induced tree mortality are all expected to increase during the 21st century. These direct and indirect climate-change effects are likely to cause losses of ecosystem services in some areas, but may also improve and expand ecosystem services in others. Some areas may be particularly vulnerable because current infrastructure and resource production are based on past climate and steady-state conditions. The ability of communities with resource-based economies to adapt to climate change is linked to their direct exposure to these changes, as well as to the social and institutional structures present in each environment. Human communities that have diverse economies and are resilient to change today will also be prepared for future climatic stresses.
Spatiotemporal patterns of terrestrial carbon cycle during the 20th century
We evaluated how climate change, rising atmospheric CO2 concentration, and land use change influenced the terrestrial carbon (C) cycle for the last century using a process-based ecosystem model. Over the last century, the modeled land use change emitted about 129 Pg of C to the atmosphere. .... Generally, interannual changes of carbon fluxes in tropical and temperate ecosystems are mainly explained by precipitation variability, while temperature variability plays a major role in boreal ecosystems.
Incorporating climate change adaptation into national conservation assessments
The Convention on Biological Diversity requires that member nations establish protected area networks that are representative of the country’s biodiversity. The identification of priority sites to achieve outstanding representation targets is typically accomplished through formal conservation assessments. However, representation in conservation assessments or gap analyses has largely been interpreted based on a static view of biodiversity. In a rapidly changing climate, the speed of changes in biodiversity distribution and abundance is causing us to rethink the viability of this approach. Here we describe three explicit strategies for climate change adaptation as part of national conservation assessments: conserving the geophysical stage, identifying and protecting climate refugia, and promoting cross- environment connectivity. We demonstrate how these three approaches were integrated into a national terrestrial conservation assessment for Papua New Guinea, one of the most biodiverse countries on earth. Protected areas identified based on representing geophysical diversity were able to capture over 90% of the diversity in vegetation communities, suggesting they could help protect representative biodiversity regardless of changes in the distribution of species and communities. By including climate change refugia as part of the national conservation assessment, it was possible to substantially reduce the amount of environmental change expected to be experienced within protected areas, without increasing the overall cost of the protected area network. Explicitly considering environmental heterogeneity between adjacent areas resulted in protected area networks with over 40% more internal environmental connectivity. These three climate change adaptation strategies represent defensible ways to guide national conserva- tion priority given the uncertainty that currently exists in our ability to predict climate changes and their impacts. Importantly, they are also consistent with data and expertise typically available during national conservation assessments, including in developing nations. This means that in the vast majority of countries, these strategies could be implemented immediately. Keywords: biodiversity, connectivity, convention on biological diversity, gap analyses, geophysical classification, Marxan, Papua New Guinea, protected areas, refugia, systematic conservation planning
Effects of drought on avian community structure
Droughts are expected to become more frequent under global climate change. Avifauna depend on precipitation for hydration, cover, and food. While there are indications that avian communities respond negatively to drought, little is known about the response of birds with differing functional and behavioural traits, what time periods and indicators of drought are most relevant, or how response varies geographically at broad spatial scales. Our goals were thus to determine (1) how avian abundance and species richness are related to drought, (2) whether community variations are more related to vegetation vigour or precipitation deviations and at what time periods relationships were strongest, (3) how response varies among avian guilds, and (4) how response varies among ecoregions with different precipitation regimes. Using mixed effect models and 1989–2005 North American Breeding Bird Survey data over the central United States, we examined the response to 10 precipitation- and greenness- based metrics by abundance and species richness of the avian community overall, and of four behavioural guilds. Drought was associated with the most negative impacts on avifauna in the semiarid Great Plains, while positive responses were observed in montane areas. Our models predict that in the plains, Neotropical migrants respond the most negatively to extreme drought, decreasing by 13.2% and 6.0% in abundance and richness, while permanent resident abundance and richness increase by 11.5% and 3.6%, respectively in montane areas. In most cases, response of abundance was greater than richness and models based on precipitation metrics spanning 32-week time periods were more supported than those covering shorter time periods and those based on greenness. While drought is but one of myriad environmental variations birds encounter, our results indicate that drought is capable of imposing sizable shifts in abundance, richness, and composition on avian communities, an important implica- tion of a more climatically variable future. Keywords: abundance, birds, drought, Great Plains, greenness, mixed effects models, North American Breeding Bird Survey, precipitation, richness, United States
Climate change and the invasion of California by grasses
Over the next century, changes in the global climate are expected to have major consequences for plant communities, possibly including the exacerbation of species invasions. We evaluated this possibility in the grass flora of California, which is economically and ecologically important and heavily invaded. We used a novel, trait-based approach involving two components: identifying differences in trait composition between native and exotic components of the grass flora and evaluating contemporary trait–climate relationships across the state. The combination of trait–climate relationships and trait differences between groups allows us to predict changes in the exotic-native balance under climate change scenarios. Exotic species are more likely to be annual, taller, with larger leaves, larger seeds, higher specific leaf area, and higher leaf N percentage than native species. Across the state, all these traits are associated with regions with higher temperature. Therefore, we predict that increasing temperatures will favor trait states that tend to be possessed by exotic species, increasing the dominance of exotic species. This prediction is corroborated by the current distribution of exotic species richness relative to native richness in California; warmer areas contain higher proportions of exotic species. This pattern was very well captured by a simple model that predicts invasion severity given only the trait–climate relationship for native species and trait differences between native and exotic species. This study provides some of the first evidence for an important interaction between climate change and species invasions across very broad geographic and taxonomic scales.
On the forest cover–water yield debate: from demand- to supply-side thinking
Several major articles from the past decade and beyond conclude the impact of reforestation or afforestation on water yield is negative: additional forest cover will reduce and removing forests will raise downstream water availability. A second group of authors argue the opposite: planting additional forests should raise downstream water availability and intensify the hydrologic cycle. Obtaining supporting evidence for this second group of authors has been more dif- ficult due to the larger scales at which the positive effects of forests on the water cycle may be seen. We argue that for- est cover is inextricably linked to precipitation. Forest-driven evapotranspiration removed from a particular catchment contributes to the availability of atmospheric moisture vapor and its cross-continental transport, raising the likelihood of precipitation events and increasing water yield, in particular in continental interiors more distant from oceans. Sea- sonal relationships heighten the importance of this phenomenon. We review the arguments from different scales and perspectives. This clarifies the generally beneficial relationship between forest cover and the intensity of the hydro- logic cycle. While evidence supports both sides of the argument – trees can reduce runoff at the small catchment scale – at larger scales, trees are more clearly linked to increased precipitation and water availability. Progressive deforesta- tion, land conversion from forest to agriculture and urbanization have potentially negative consequences for global precipitation, prompting us to think of forest ecosystems as global public goods. Policy-making attempts to measure product water footprints, estimate the value of ecosystem services, promote afforestation, develop drought mitigation strategies and otherwise manage land use must consider the linkage of forests to the supply of precipitation. Keywords: afforestation, climate change adaptation, forest ecosystem services, precipitation recycling, water yield
Temperature and precipitation controls over leaf- and ecosystem-level CO2 flux along a woody plant encroachment gradient
Conversion of grasslands to woodlands may alter the sensitivity of CO2 exchange of individual plants and entire ecosystems to air temperature and precipitation. We combined leaf-level gas exchange and ecosystem-level eddy covariance measurements to quantify the effects of plant temperature sensitivity and ecosystem temperature responses within a grassland and mesquite woodland across seasonal precipitation periods. In so doing, we were able to estimate the role of moisture availability on ecosystem temperature sensitivity under large-scale vegetative shifts. Optimum temperatures (Topt) for net photosynthetic assimilation (A) and net ecosystem productivity (NEP) were estimated from a function fitted to A and NEP plotted against air temperature. The convexities of these tem- perature responses were quantified by the range of temperatures over which a leaf or an ecosystem assimilated 50% of maximum NEP (Ω50). Under dry pre- and postmonsoon conditions, leaf-level Ω50 in C3 shrubs were two-to-three times that of C4 grasses, but under moist monsoon conditions, leaf-level Ω50 was similar between growth forms. At the ecosystems-scale, grassland NEP was more sensitive to precipitation, as evidenced by a 104% increase in maxi- mum NEP at monsoon onset, compared to a 57% increase in the woodland. Also, woodland NEP was greater across all temperatures experienced by both ecosystems in all seasons. By maintaining physiological function across a wider temperature range during water-limited periods, woody plants assimilated larger amounts of carbon. This higher carbon-assimilation capacity may have significant implications for ecosystem responses to projected climate change scenarios of higher temperatures and more variable precipitation, particularly as semiarid regions experi- ence conversions from C4 grasses to C3 shrubs. As regional carbon models, CLM 4.0, are now able to incorporate functional type and photosynthetic pathway differences, this work highlights the need for a better integration of the interactive effects of growth form/functional type and photosynthetic pathway on water resource acquisition and temperature sensitivity. Keywords: eddy covariance, mesquite (Prosopis velutina), net ecosystem exchange, photosynthesis, respiration, temperature optima, vegetative change, woody plant encroachment
