Climate Science Documents
Biodiversity Under Global Change
Many common plant species, such as prairie grasses, have evolved traits for the efficient capture and use of two key resources that limit terrestrial productivity: nitrogen (N) and carbon dioxide (CO2). Over the past 60 years, human activity has vastly increased the availability of these resources. Atmospheric CO2 concentration has increased by 40%, and N availability has more than doubled. These changes are likely to have important consequences for species interactions, community structure, and ecosystem functioning. On page 1399 of this issue, Reich investigates one important consequence, biodiversity loss, based on a long-term elevated CO2 and nitrogen fertilization experiment.
Peatland Response to Global Change
Peatlands can buffer the impact of external perturbations, but can also rapidly shift to a new ecosystem type, with large gains or losses of stored carbon. VOL 326 SCIENCE
Amid Worrisome Signs of Warming, ‘Climate Fatigue’ Sets In
As scientists debate whether climate is changing faster than anticipated, some worry that a drumbeat of dire warnings may be helping to erode U.S. public concerns about global warming
Biodiversity and Climate Change
Efforts to elucidate the effect of climate change on biodiversity with detailed data sets and refined models reach novel conclusions.
Drought Sensitivity of the Amazon Rainforest
Amazon forests are a key but poorly understood component of the global carbon cycle. If, as anticipated, they dry this century, they might accelerate climate change through carbon losses and changed surface energy balances. We used records from multiple long-term monitoring plots across Amazonia to assess forest responses to the intense 2005 drought, a possible analog of future events. Affected forest lost biomass, reversing a large long-term carbon sink, with the greatest impacts observed where the dry season was unusually intense. Relative to pre-2005 conditions, forest subjected to a 100-millimeter increase in water deficit lost 5.3 megagrams of aboveground biomass of carbon per hectare. The drought had a total biomass carbon impact of 1.2 to 1.6 petagrams (1.2 × 1015 to 1.6 × 1015 grams). Amazon forests therefore appear vulnerable to increasing moisture stress, with the potential for large carbon losses to exert feedback on climate change.
The Genetic Architecture of Maize Flowering Time
Flowering time is a complex trait that controls adaptation of plants to their local environment in the outcrossing species Zea mays (maize). We dissected variation for flowering time with a set of 5000 recombinant inbred lines (maize Nested Association Mapping population, NAM). Nearly a million plants were assayed in eight environments but showed no evidence for any single largeeffect quantitative trait loci (QTLs). Instead, we identified evidence for numerous small-effect QTLs shared among families; however, allelic effects differ across founder lines. We identified no individual QTLs at which allelic effects are determined by geographic origin or large effects for epistasis or environmental interactions. Thus, a simple additive model accurately predicts flowering time for maize, in contrast to the genetic architecture observed in the selfing plant species rice and Arabidopsis.
A-maize-ing Diversity
Analysis of a new maize resource reveals that a large number of genetic loci with small effects may underlie the wide variation seen in traits such as flowering time.
Phenology Feedbacks on Climate Change
A longer growing season as a result of climate change will in turn affect climate through biogeochemical and biophysical effects. SCIENCE VOL 324
Risks of Climate Engineering
Observations indicate that attempts to limit climate warming by reducing incoming shortwave radiation risk major precipitation changes.
Seasons and Life Cycles
A conceptual framework. This table is a guide to determining how individual species are responding to an extended growing season by observing the duration of peak season. The life history of a species—from the onset of greening through the end of senescence—is illustrated by the length of the solid lines. Each case represents a shift in the timing (columns) and duration (rows) of one or more species in a hypothetical three-species community that includes an early-, mid-, and late-season species. The growing season begins when the first species greens and ends when the last species senesces. The peak season (gray shaded area) occurs when all species have started and none have completed their life history. Reproductive life history events likely begin before the peak season and are completed before its end. The final row and column list changes that can be observed through frequent observations of surface greenness.
The Last Glacial Maximum
We used 5704 14C, 10Be, and 3 He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ~14.5 ka.
Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America
Although the North American megafaunal extinctions and the formation of novel plant communities are well-known features of the last deglaciation, the causal relationships between these phenomena are unclear. Using the dung fungus Sporormiella and other paleoecological proxies from Appleman Lake, Indiana, and several New York sites, we established that the megafaunal decline closely preceded enhanced fire regimes and the development of plant communities that have no modern analogs. The loss of keystone megaherbivores may thus have altered ecosystem structure and function by the release of palatable hardwoods from herbivory pressure and by fuel accumulation. Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions and during the BøllingAllerød warm period. Human impacts remain plausible, but the decline predates Younger Dryas cooling and the extraterrestrial impact event proposed to have occurred 12,900 years ago.
Megafaunal Decline and Fall
Declines in North American megafauna populations began before the Clovis period and were the cause, not the result, of vegetation changes and increased fires.
Warming Up Food Webs
How do predator-prey interactions influence Warming Up Food Webs ecosystem responses to climate change? VOL 323 SCIENCE
Reducing Greenhouse Gas Emissions from Deforestation and ForestDegradation: Global Land-Use Implications
Recent climate talks in Bali have made progress toward action on deforestation and forest degradation in developing countries, within the anticipated post-Kyoto emissions reduction agreements. As a result of such action, many forests will be better protected, but some land-use change will be displaced to other locations. The demonstration phase launched at Bali offers an opportunity to examine potential outcomes for biodiversity and ecosystem services. Research will be needed into selection of priority areas for reducing emissions from deforestation and forest degradation to deliver multiple benefits, on-the-ground methods to best ensure these benefits, and minimization of displaced land-use change into nontarget countries and ecosystems, including through revised conservation investments
Ecological Restoration in the Light of Ecological History
Ecological history plays many roles in ecological restoration, most notably as a tool to identify and characterize appropriate targets for restoration efforts. However, ecological history also reveals deep human imprints on many ecological systems and indicates that secular climate change has kept many targets moving at centennial to millennial time scales. Past and ongoing environmental changes ensure that many historical restoration targets will be unsustainable in the coming decades. Ecological restoration efforts should aim to conserve and restore historical ecosystems where viable, while simultaneously preparing to design or steer emerging novel ecosystems to ensure maintenance of ecological goods and services.
Stationarity Is Dead: Whither Water Management?
Climate change undermines a basic assumption that historically has facilitated management of water supplies, demands, and risks. SCIENCE VOL 319
A Determination of the Cloud Feedback from Climate Variations over the Past Decade
Estimates of Earth's climate sensitivity are uncertain, largely because of uncertainty in the long-term cloud feedback. I estimated the magnitude of the cloud feedback in response to short-term climate variations by analyzing the top-of-atmosphere radiation budget from March 2000 to February 2010. Over this period, the short-term cloud feedback had a magnitude of 0.54 T 0.74 (2s) watts per square meter per kelvin, meaning that it is likely positive. A small negative feedback is possible, but one large enough to cancel the climate’s positive feedbacks is not supported by these observations. Both long- and short-wave components of short-term cloud feedback are also likely positive. Calculations of short-term cloud feedback in climate models yield a similar feedback. I find no correlation in the models between the short- and long-term cloud feedbacks.
Modeling Effects of Environmental Change on Wolf Population Dynamics, Trait Evolution, and Life History
Environmental change has been observed to generate simultaneous responses in population dynamics, life history, gene frequencies, and morphology in a number of species. But how common are such eco-evolutionary responses to environmental change likely to be? Are they inevitable, or do they require a specific type of change? Can we accurately predict eco-evolutionary responses? We address these questions using theory and data from the study of Yellowstone wolves. We show that environmental change is expected to generate eco-evolutionary change, that changes in the average environment will affect wolves to a greater extent than changes in how variable it is, and that accurate prediction of the consequences of environmental change will probably prove elusive.
Beyond Predictions: Biodiversity Conservation in a Changing Climate
Climate change is predicted to become a major threat to biodiversity in the 21st century, but accurate predictions and effective solutions have proved difficult to formulate. Alarming predictions have come from a rather narrow methodological base, but a new, integrated science of climate-change biodiversity assessment is emerging, based on multiple sources and approaches. Drawing on evidence from paleoecological observations, recent phenological and microevolutionary responses, experiments, and computational models, we review the insights that different approaches bring to anticipating and managing the biodiversity consequences of climate change, including the extent of species’ natural resilience. We introduce a framework that uses information from different sources to identify vulnerability and to support the design of conservation responses. Although much of the information reviewed is on species, our framework and conclusions are also applicable to ecosystems, habitats, ecological communities, and genetic diversity, whether terrestrial, marine, or fresh water.
The Hot Summer of 2010: Redrawing the Temperature Record Map of Europe
The summer of 2010 was exceptionally warm in eastern Europe and large parts of Russia. We provide evidence that the anomalous 2010 warmth that caused adverse impacts exceeded the amplitude and spatial extent of the previous hottest summer of 2003. 'Mega-heatwaves' such as the 2003 and 2010 events broke the 500-yr long seasonal temperature records over approximately 50% of Europe. According to regional multi-model experiments, the probability of a summer experiencing 'megaheatwaves' will increase by a factor of 5 to 10 within the next 40 years. However, the magnitude of the 2010 event was so extreme that despite this increase, the occurrence of an analogue over the same region remains fairly unlikely until the second half of the 21st century.
Global Resilience of Tropical Forest and Savanna to Critical Transitions
It has been suggested that tropical forest and savanna could represent alternative stable states, implying critical transitions at tipping points in response to altered climate or other drivers. So far, evidence for this idea has remained elusive, and integrated climate models assume smooth vegetation responses. We analyzed data on the distribution of tree cover in Africa, Australia, and South America to reveal strong evidence for the existence of three distinct attractors: forest, savanna, and a treeless state. Empirical reconstruction of the basins of attraction indicates that the resilience of the states varies in a universal way with precipitation. These results allow the identification of regions where forest or savanna may most easily tip into an alternative state, and they pave the way to a new generation of coupled climate models.
Time to Adapt to a Warming World, But Where’s the Science?
With dangerous global warming seemingly inevitable, users of climate information— from water utilities to international aid workers—are turning to climate scientists for guidance. But usable knowledge is in short supply VOL 334 SCIENCE
The 2010 Amazon Drought
Several global circulation models (GCMs) project an increase in the frequency and severity of drought events affecting the Amazon region as a consequence of anthropogenic greenhouse gas emissions (1). The proximate cause is twofold, increasing Pacific sea surface temperatures (SSTs), which may intensify El Niño Southern Oscillation events and associated periodic Amazon droughts, and an increase in the frequency of historically rarer droughts associated with high Atlantic SSTs and northwest displacement of the intertropical convergence zone (1, 2). Such droughts may lead to a loss of some Amazon forests, which would accelerate climate change (3). In 2005, a major Atlantic SST–associated drought occurred, identified as a 1-in-100-year event (2). Here, we report on a second drought in 2010, when Atlantic SSTs were again high.
Climate Outlook Looking Much The Same, or Even Worse
Climate scientists have been feverishly preparing analyses for inclusion in the fifth climate assessment report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) due out in 2013. At the meeting, they gave colleagues a peek at where climate science stands 5 years after their last push to inform the authoritative international evaluation . The climate models are bigger and more sophisticated than ever, speakers reported, but they are yielding the same wide range of possible warming and precipitation changes as they did 5 years ago. But when polled on other areas of concern, researchers say they see more trouble ahead than the previous IPCC assessment had, though less than some scientists had feared
The Global Extent and Determinants of Savanna and Forest as Alternative Biome States
Theoretically, fire–tree cover feedbacks can maintain savanna and forest as alternative stable states. However, the global extent of fire-driven discontinuities in tree cover is unknown, especially accounting for seasonality and soils. We use tree cover, climate, fire, and soils data sets to show that tree cover is globally discontinuous. Climate influences tree cover globally but, at intermediate rainfall (1000 to 2500 millimeters) with mild seasonality (less than 7 months), tree cover is bimodal, and only fire differentiates between savanna and forest. These may be alternative states over large areas, including parts of Amazonia and the Congo. Changes in biome distributions, whether at the cost of savanna (due to fragmentation) or forest (due to climate), will be neither smooth nor easily reversible.
Navigating the Anthropocene: Improving Earth System Governance
The United Nations conference in Rio de Janeiro in June is an important opportunity to improve the institutional framework for sustainable development. VOL 335 SCIENCE
Impacts of Biodiversity Loss
How much diversity is needed to maintain the productivity of ecosystems? VOL 336 SCIENCE
Generic Indicators for Loss of Resilience Before a Tipping Point Leading to Population Collapse
Theory predicts that the approach of catastrophic thresholds in natural systems (e.g., ecosystems, the climate) may result in an increasingly slow recovery from small perturbations, a phenomenon called critical slowing down. We used replicate laboratory populations of the budding yeast Saccharomyces cerevisiae for direct observation of critical slowing down before population collapse. We mapped the bifurcation diagram experimentally and found that the populations became more vulnerable to disturbance closer to the tipping point. Fluctuations of population density increased in size and duration near the tipping point, in agreement with the theory. Our results suggest that indicators of critical slowing down can provide advance warning of catastrophic thresholds and loss of resilience in a variety of dynamical systems. SCIENCE VOL 336 1
Ocean Salinities Reveal Strong Global Water Cycle Intensification During 1950 to 2000
Fundamental thermodynamics and climate models suggest that dry regions will become drier and wet regions will become wetter in response to warming. Efforts to detect this long-term response in sparse surface observations of rainfall and evaporation remain ambiguous. We show that ocean salinity patterns express an identifiable fingerprint of an intensifying water cycle. Our 50-year observed global surface salinity changes, combined with changes from global climate models, present robust evidence of an intensified global water cycle at a rate of 8 T 5% per degree of surface warming. This rate is double the response projected by current-generation climate models and suggests that a substantial (16 to 24%) intensification of the global water cycle will occur in a future 2° to 3° warmer world. SCIENCE VOL 336
The Greenhouse Is Making the Water-Poor Even Poorer
How bad will global warming get? The question has long been cast in terms of how hot the world will get. But perhaps more important to the planet’s inhabitants will be how much rising greenhouse gases crank up the water cycle. Theory and models predict that a strengthening greenhouse will increase precipitation where it is already relatively high—tropical rain forests, for example— and decrease it where it is already low, as in the subtropics. SCIENCE VOL 336 27 APRIL 2012
Plant Species Richness and Ecosystem Multifunctionality in Global Drylands
Experiments suggest that biodiversity enhances the ability of ecosystems to maintain multiple functions, such as carbon storage, productivity, and the buildup of nutrient pools (multifunctionality). However, the relationship between biodiversity and multifunctionality has never been assessed globally in natural ecosystems. We report here on a global empirical study relating plant species richness and abiotic factors to multifunctionality in drylands, which collectively cover 41% of Earth’s land surface and support over 38% of the human population. Multifunctionality was positively and significantly related to species richness. The best-fitting models accounted for over 55% of the variation in multifunctionality and always included species richness as a predictor variable. Our results suggest that the preservation of plant biodiversity is crucial to buffer negative effects of climate change and desertification in drylands.
Financial Costs of Meeting Global Biodiversity Conservation Targets: Current Spending and Unmet Needs
World governments have committed to halting human-induced extinctions and safeguarding important sites for biodiversity by 2020, but the financial costs of meeting these targets are largely unknown. We estimate the cost of reducing the extinction risk of all globally threatened bird species (by ≥1 International Union for Conservation of Nature Red List category) to be U.S. $0.875 to $1.23 billion annually over the next decade, of which 12% is currently funded. Incorporating threatened nonavian species increases this total to U.S. $3.41 to $4.76 billion annually. We estimate that protecting and effectively managing all terrestrial sites of global avian conservation significance (11,731 Important Bird Areas) would cost U.S. $65.1 billion annually. Adding sites for other taxa increases this to U.S. $76.1 billion annually. Meeting these targets will require conservation funding to increase by at least an order of magnitude.
Simultaneously Mitigating Near-Term Climate Change and Improving Human Health and Food Security
Tropospheric ozone and black carbon (BC) contribute to both degraded air quality and global warming. We considered ~400 emission control measures to reduce these pollutants by using current technology and experience. We identified 14 measures targeting methane and BC emissions that reduce projected global mean warming ~0.5°C by 2050. This strategy avoids 0.7 to 4.7 million annual premature deaths from outdoor air pollution and increases annual crop yields by 30 to 135 million metric tons due to ozone reductions in 2030 and beyond. Benefits of methane emissions reductions are valued at $700 to $5000 per metric ton, which is well above typical marginal abatement costs (less than $250). The selected controls target different sources and influence climate on shorter time scales than those of carbon dioxide–reduction measures. Implementing both substantially reduces the risks of crossing the 2°C threshold.
Carbon Storage with Benefits
Biochar—a material related to charcoal—has the potential to benefit farming as well as mitigate climate change.
Biotic Multipliers of Climate Change
A focus on species interactions may improve predictions of the effects of climate change on ecosystems.
Old Trees: Extraction, Conservation Can Coexist
BECAUSE LARGE OLD TREES ARE ESSENTIAL FOR FOREST ECOSYSTEM INTEGRITY AND BIODIVERsity, timber extraction in managed forests should preferentially be concentrated where large old trees are least likely to develop (“Global decline in large old trees,” D. B. Lindenmayer et al., Perspectives, 7 December 2012, p. 1305). However, timber extraction and the conservation of large old trees are not necessarily mutually exclusive. Current forest policy and management practices in Flanders, Belgium, aim to convert even-aged stands (areas in which trees are all the same age) to stands with trees of varying ages in an effort to increase forest ecosystem stability and resilience and to allow trees to grow old. As part of their ecologically sustainable forest management, public forest managers have adopted a large-tree retention approach [see also (1, 2)]. Tree islands within stands managed for production of high-quality timber are reserved for conservation, and trees within these islands will never be extracted. Large old trees of commercially valuable species that have grown beyond the commercially optimal dimensions will not be logged either. And no tree beyond a threshold diameter [currently set at dbh (diameter at breast height) of more than 102 cm] will ever be logged. The strip-shelterwood system (in which trees are cut in linear strips and surrounding trees are given time to grow old) and the coppice-with-standards system (in which some trees are left to grow while others around them are cut) are two examples of forest management that allows the combination of sustainable forest exploitation and conservation of large old trees
What Does Zero Deforestation Mean?
Ambiguous defi nitions and metrics create risks for forest conservation and accountability. SCIENCE VOL 342
Physical Laws Shape Biology
IN THE PERSPECTIVE “A DYNAMICAL-SYSTEMS VIEW OF STEM CELL biology” (12 October 2012, p. 215), C. Furusawa and K. Kaneko discuss the relevance of dynamic systems biology approaches and the concept of “attractors” to understand cell differentiation and proliferation. We share their excitement in using computational models that apply physical laws to cell fate decision.
Water in the Balance
Satellite data may enable improved management of regional groundwater reserves. VOL 340 SCIENCE
Enhanced Seasonal Exchange of CO2 by Northern Ecosystems Since 1960
Seasonal variations of atmospheric carbon dioxide (CO2) in the Northern Hemisphere have increased since the 1950s, but sparse observations have prevented a clear assessment of the patterns of long-term change and the underlying mechanisms. We compare recent aircraft-based observations of CO2 above the North Pacific and Arctic Oceans to earlier data from 1958 to 1961 and find that the seasonal amplitude at altitudes of 3 to 6 km increased by 50% for 45° to 90°N but by less than 25% for 10° to 45°N. An increase of 30 to 60% in the seasonal exchange of CO2 by northern extratropical land ecosystems, focused on boreal forests, is implicated, substantially more than simulated by current land ecosystem models. The observations appear to signal large ecological changes in northern forests and a major shift in the global carbon cycle.
Pathways for Conservation
NEXT WEEK, CONSERVATION SCIENTISTS WILL GATHER AT THE INTERNATIONAL CONGRESS FOR Conservation Biology (ICCB) in Baltimore, Maryland, to grapple with the challenges of preserving our natural world in the face of a growing and increasingly consumptive human population. The natural world provides countless services, such as clean water, protection from fl ooding, and carbon sequestration, while offering opportunities for new medicines, foods, and energy production. Yet these valuable services and opportunities are disappearing along with the species and natural areas that supply them. The needs of a growing human population must be met while conserving the planet’s natural systems. Accomplishing both will depend on making clearer connections between scientifi c results regarding issues such as biodiversity loss and the critical decisions that must be made about conditions that underlie change, such as greenhouse gas emissions and freshwater availability. The good news is that today’s conservation scientists are developing innovative tools and strategies. SCIENCE VOL 341
A Reconstruction of Regional and Global Temperature for the Past 11,300 Years
Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time. Here we provide a broader perspective by reconstructing regional and global temperature anomalies for the past 11,300 years from 73 globally distributed records. Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C cooling through the middle to late Holocene (<5000 years ago), culminating in the coolest temperatures of the Holocene during the Little Ice Age, about 200 years ago. This cooling is largely associated with ~2°C change in the North Atlantic. Current global temperatures of the past decade have not yet exceeded peak interglacial values but are warmer than during ~75% of the Holocene temperature history. Intergovernmental Panel on Climate Change model projections for 2100 exceed the full distribution of Holocene temperature under all plausible greenhouse gas emission scenarios.
Is Embracing Change Our Best Bet?
Restoration ecology and conservation biology are both under pressure to adapt to accelerated anthropogenic global change. Pristine areas free from human infl uence no longer exist and, arguably, have not for thousands of years ( 1). Major landcover transformations for agriculture affected vast territories more than 3000 years ago ( 2). Large mammal extinctions in the late Pleistocene (circa 12,000 years ago) were related to human expansion ( 3). And relocation of nowwidespread naturalized species was already happening 4230 years ago, when domestic dogs (dingos) were introduced into Australia by way of southeast Asia ( 4). Thus, humansculpted landscapes are what we have been mostly managing for millennia. Because the rate of alteration has dramatically increased over the past 200 years, those ancient localized impacts now affect most of the world. Additionally, other indirect impacts act at a planetary scale—e.g., increased carbon dioxide concentration and nitrogen deposition
Hell and High Water: PracticeRelevant Adaptation Science
Adaptation requires science that analyzes decisions, identifies vulnerabilities, improves foresight, and develops options
Marine Taxa Track Local Climate Velocities
Organisms are expected to adapt or move in response to climate change, but observed distribution shifts span a wide range of directions and rates. Explanations often emphasize biological distinctions among species, but general mechanisms have been elusive. We tested an alternative hypothesis: that differences in climate velocity—the rate and direction that climate shifts across the landscape—can explain observed species shifts. We compiled a database of coastal surveys around North America from 1968 to 2011, sampling 128 million individuals across 360 marine taxa. Climate velocity explained the magnitude and direction of shifts in latitude and depth much more effectively than did species characteristics. Our results demonstrate that marine species shift at different rates and directions because they closely track the complex mosaic of local climate velocities. SCIENCE VOL 341 13 SEPTEMBER 2013
Monsoon Melee
The rhythms of life across South Asia depend on the Indian monsoon. Climate scientists are locking horns over the cause of the summer deluges
Climate Change Conversations
THE THOUSANDS OF PRESENTATIONS AT NEXT WEEK’S MEETING OF THE AMERICAN CHEMICAL SOCIETY (ACS) in New Orleans exemplify one of the many ways scientists converse among themselves about the most recent advances in science. Science and technology continue to reshape the world we live in, and appreciating how these changes, both intended and unintended, come about is a necessity for all citizens in a democratic society. Scientists have a responsibility to help their fellow citizens understand what science and technology can and cannot do for them
The Global Plight of Pollinators
Wild pollinators are in decline, and managed honeybees cannot compensate for their loss. 29 MARCH 2013 VOL 339 SCIENCE
Wildlife decline and social conflict
Policies aimed at reducing wildlife-related conflict must address the underlying causes
Assemblage Time Series Reveal Biodiversity Change but Not Systematic Loss
The extent to which biodiversity change in local assemblages contributes to global biodiversity loss is poorly understood. We analyzed 100 time series from biomes across Earth to ask how diversity within assemblages is changing through time. We quantified patterns of temporal a diversity, measured as change in local diversity, and temporal b diversity, measured as change in community composition. Contrary to our expectations, we did not detect systematic loss of a diversity. However, community composition changed systematically through time, in excess of predictions from null models. Heterogeneous rates of environmental change, species range shifts associated with climate change, and biotic homogenization may explain the different patterns of temporal a and b diversity. Monitoring and understanding change in species composition should be a conservation priority.
From Past to Future Warming
Analyses of past observations help to predict the human contribution to future climate change. 21 FEBRUARY 2014 VOL 343 SCIENCE
Carbon Market Lessons and Global Policy Outlook
Summary: Ongoing work on linking markets and mixing policies builds on successes and failures in pricing and trading carbon. Closing sentence, 1st paragraph: Are carbon markets seriously challenged or succeeding and on the rise?
Status and Ecological Effects of the World’s Largest Carnivores
The largest terrestrial species in the order Carnivora are wide-ranging and rare because of their positions at the top of food webs. They are some of the world’s most admired mammals and, ironically, some of the most imperiled. Most have experienced substantial population declines and range contractions throughout the world during the past two centuries. Because of the high metabolic demands that come with endothermy and large body size, these carnivores often require large prey and expansive habitats. These food requirements and wide-ranging behavior often bring them into confl ict with humans and livestock. This, in addition to human intolerance, renders them vulnerable to extinction. Large carnivores face enormous threats that have caused massive declines in their populations and geographic ranges, including habitat loss and degradation, persecution, utilization, and depletion of prey. We highlight how these threats can affect the conservation status and ecological roles of this planet’s 31 largest carnivores.
Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years
During the Middle Miocene, when temperatures were ~3° to 6°C warmer and sea level 25 to 40 meters higher than present, pCO2 was similar to modern levels.
Changes in Wind Pattern Alter Albatross Distribution and Life-History Traits
Westerly winds in the Southern Ocean have increased in intensity and moved poleward. Using long-term demographic and foraging records, we show that foraging range in wandering albatrosses has shifted poleward in conjunction with these changes in wind pattern, while their rates of travel and flight speeds have increased. Consequently, the duration of foraging trips has decreased, breeding success has improved, and birds have increased in mass by more than 1 kilogram. These positive consequences of climate change may be temporary if patterns of wind in the southern westerlies follow predicted climate change scenarios. This study stresses the importance of foraging performance as the key link between environmental changes and population processes.
Freshwater Methane Emissions Offset the Continental Carbon Sink
Acornerstone of our understanding of the contemporary global carbon cycle is that the terrestrial land surface is an important greenhouse gas (GHG) sink (1, 2). The global land sink is estimated to be 2.6 T 1.7 Pg of C year−1 (variability T range, excluding C emissions because of deforestation) (1). Lakes, impoundments, and rivers are parts of the terrestrial landscape, but they have not yet been included in the terrestrial GHG balance (3, 4). Available data suggest, however, that freshwaters can be substantial sources of CO2 (3, 5) and CH4 (6). Over time, soil carbon reaches freshwaters by lateral hydrological transport, where it can meet several fates, including burial in sediments, further transport to the sea, or evasion to the atmosphere as CO2 or CH4 (7). CH4 emissions may be small in terms of carbon, but CH4 is a more potent GHG than CO2 over century time scales. This study indicates that global CH4 emissions expressed as CO2 equivalents correspond to at least 25% of the estimated terrestrial GHG sink.
Not All About Consumption
Resource exploitation can lead to increased ecological impacts even when overall consumption levels stay the same 15 March 2013 VOL 339 SCIENCE
Defaunation in the Anthropocene
We live amid a global wave of anthropogenically driven biodiversity loss: species and population extirpations and, critically, declines in local species abundance. Particularly, human impacts on animal biodiversity are an under-recognized form of global environmental change. Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance. Invertebrate patterns are equally dire: 67% of monitored populations show 45% mean abundance decline. Such animal declines will cascade onto ecosystem functioning and human well-being. Much remains unknown about this “Anthropocene defaunation”; these knowledge gaps hinder our capacity to predict and limit defaunation impacts. Clearly, however, defaunation is both a pervasive component of the planet’s sixth mass extinction and also a major driver of global ecological change 25 JULY 2014 • VOL 345 ISSUE 6195
How Does Climate Change Affect Biodiversity?
The most recent and complex bioclimate models excel at describing species’ current distributions. Yet, it is unclear which models will best predict how climate change will affect their future distributions. 8 SEPTEMBER 2006 VOL 313 SCIENCE
Changes in Climatic Water Balance Drive Downhill Shifts in Plant Species’ Optimum Elevations
Uphill shifts of species’ distributions in response to historical warming are well documented, which leads to widespread expectations of continued uphill shifts under future warming. Conversely, downhill shifts are often considered anomalous and unrelated to climate change. By comparing the altitudinal distributions of 64 plant species between the 1930s and the present day within California, we show that climate changes have resulted in a significant downward shift in species’ optimum elevations. This downhill shift is counter to what would be expected given 20th-century warming but is readily explained by species’ niche tracking of regional changes in climatic water balance rather than temperature. Similar downhill shifts can be expected to occur where future climate change scenarios project increases in water availability that outpace evaporative demand.
The Greening of Synfuels
An old, dirty technology to make transportation fuels from coal could fight global warming, say proponents. The trick is using more biomass and burying the carbon dioxide that’s generated 18 APRIL 2008 VOL 320 SCIENCE
All Downhill From Here?
Biologists say climate change may already be affecting high-mountain ecosystems around the world, where plants and animals adapted to cold, barren conditions now face higher temperatures and a surge of predators and competitors
Human Evolution Out of Africa: The Role of Refugia and Climate Change
Although an African origin of the modern human species is generally accepted, the evolutionary processes involved in the speciation, geographical spread, and eventual extinction of archaic humans outside of Africa are much debated. An additional complexity has been the recent evidence of limited interbreeding between modern humans and the Neandertals and Denisovans. Modern human migrations and interactions began during the buildup to the Last Glacial Maximum, starting about 100,000 years ago. By examining the history of other organisms through glacial cycles, valuable models for evolutionary biogeography can be formulated. According to one such model, the adoption of a new refugium by a subgroup of a species may lead to important evolutionary changes.
Rescuing Wolves from Politics: Wildlife as a Public Trust Resource
Long-term conservation of gray wolves is possible if states recognize a legal obligation to conserve species as a public trust resource
Rapid Range Shifts of Species Associated with High Levels of Climate Warming
The distributions of many terrestrial organisms are currently shifting in latitude or elevation in responseto changing climate. Using a meta-analysis, we estimated that the distributions of species haverecently shifted to higher elevations at a median rate of 11.0 meters per decade, and to higher latitudes at a median rate of 16.9 kilometers per decade. These rates are approximately two and three times faster than previously reported. The distances moved by species are greatest in studies showing thehighest levels of warming, with average latitudinal shifts being generally sufficient to track temperature changes. However, individual species vary greatly in their rates of change, suggesting that the range shift of each species depends on multiple internal species traits and external drivers of change. Rapid average shifts derive from a wide diversity of responses by individual species.
Seeds of Change for Restoration Ecology
FORESTS PROVIDE A WIDE VARIETY OF ECOSYSTEM SERVICES, INCLUDING PROVISIONS SUCH AS food and fuel and services that affect climate and water quality (1). In light of the increasing global population pressure, we must not only conserve, but also restore forests to meet the increasing demands for ecosystem services and goods that they provide (2). Ecological restoration has recently adopted insights from the biodiversity-ecosystem function (BEF) perspective (3). This emphasis on functional rather than taxonomic diversity (3, 4), combined with increasing acceptance of perennial, global-scale effects on the environment (5, 6) and the associated species gains and losses (“Terrestrial ecosystem responses to species gains and losses,” D. A. Wardle et al., Review, 10 June, p. 1273), may be the beginning of a paradigm shift in forest conservation and restoration ecology. As a result, we may see increased tolerance toward and the use of nonnative tree species in forests worldwide 8 JULY 2011 VOL 333 SCIENCE
From Ocean to Stratosphere
Rising tropical sea surface temperatures alter atmospheric dynamics at heights of 16 kilometers or more. SCIENCE VOL 322 3 OCTOBER 2008
Linked in: Connectiong Riparian areas to support Forest Biodiversity
Many forest-dwelling species rely on both terrestrial and aquatic habitat for their survival. These species, including rare and little-understood amphibians and arthropods, live in and around headwater streams and disperse overland to neighboring headwater streams. Forest management policies that rely on riparian buffer strips and structurebased management—practices meant to preserve habitat—address only some of these habitat needs. They generally do not consider the overland connectivity necessary for these species to successfully move across a landscape to maintain genetically diverse populations. Management in headwater areas also can affect downstream salmon habitat. Landslides and debris flows initiated in these areas can severely degrade habitat by dumping too much sediment and not enough large wood into the stream. Carefully managing sensitive headwater areas can aid not only amphibians and arthropods, but also threatened salmon populations and other forest organisms. Pacific Northwest Research Station scientists are exploring scenarios for protecting headwaters by extending riparian buffers and connecting them over ridgelines to neighboring drainages. A range of management practices designed to achieve multiple objectives may be appropriate in these protected areas to facilitate cost-effective, ecologically integrated management plans. Headwater links could piggyback on lands that are already protected and could consider such factors as sensitivity to debris flows and landslides, land ownerships and objectives, and climate change.
Mount St. Helens: Still Erupting Lessons 31 Years Later
The massive volcanic eruption of Mount St. Helens 31 years ago provided the perfect backdrop for studying the earliest stages of forest development. Immediately after the eruption, some areas of the blast area were devoid of life. On other parts of the volcanic landscape, many species survived, although their numbers were greatly reduced. Reassembly began at many different starting points along the spectrum of disturbance. Within the national volcanic monument, natural regeneration generally has been allowed to proceed at its own pace. Charlie Crisafulli and Fred Swanson, scientists with the Pacific Northwest Research Station, along with numerous collaborators, have found that the sunlit environment, dominated by shrubs, herbs, and grasses that characterize early-seral ecosystems, supports complex food webs involving numerous herbivores. These biologically rich areas provide habitat for plant and animal species that are either found only in these early-seral ecosystems or reach their highest densities there. Although much of the focus of forest ecosystem management over the past 20 years in the Pacific Northwest has been on protecting old forests and hastening development of conditions associated with older forests, the research on Mount St. Helens points to the ecological value of allowing a portion of a managed landscape to develop characteristics of a complex early-seral ecosystem
Thinking Big: Linking Rivers to Landscapes
Exploring relationships between landscape characteristics and rivers is an emerging field of study, bolstered by the proliferation of satellite data, advances in statistical analysis, and increased emphasis on largescale monitoring. Climate patterns and landscape features such as road networks, underlying geology, and human developments determine the characteristics of the rivers flowing through them. A multiagency team of scientists developed novel modeling methods to link these landscape features to instream habitat and to abundance of coho salmon in Oregon coastal streams. This is the first comprehensive analysis of landscape-scale data collected as part of the state’s Oregon Plan for Salmon and Watersheds. The research team found that watershed characteristics and human activities far from the river’s edge influence the distribution and habitats of coho salmon. Although large-scale landscape characteristics can predict stream reaches that might support greater numbers of coho salmon, smaller scale features and random chance also play a role in whether coho spawn in a particular stream and in a particular year. The team developed new models that successfully predicted the distribution of instream habitat features. Volume of instream wood and pool frequency were the features most influenced by human activities. Studying these relationships can help guide large-scale monitoring and management of aquatic resources.
Seasonal Neighbors: Residential Development Encroaches on Mule Deer Winter Range in Central Oregon
Mule deer populations in central Oregon are in decline, largely because of habitat loss. Several factors are likely contributors. Encroaching juniper and invasive cheatgrass are replacing deer forage with high nutritional value, such as bitterbrush and sagebrush. Fire suppression and reduced timber harvests mean fewer acres of early successional forest, which also offer forage opportunities. Human development, including homes and roads, is another factor. It is this one that scientists with the Pacific Northwest Research Station and their collaborators investigated in a recent study. As part of an interagency assessment of the ecological effects of resort development near Bend, Oregon, researchers examined recent and potential development rates and patterns and evaluated their impact on mule deer winter range. They found that residential development in central Oregon is upsetting traditional migratory patterns, reducing available habitat, and possibly increasing stress for mule deer. Many herds of mule deer spend the summer in the Cascade Range and move to lower elevations during the winter. An increasing number of buildings, vehicle traffic, fencing, and other obstacles that accompany human land use are making it difficult for mule deer to access and use their winter habitat. The study provides valuable information for civic leaders, land use planners, and land managers to use in weighing the ecological impact of various land use decisions in central Oregon.
Ecosystem Service Markets 101: Supply and Demand for Nature
Establishing markets for ecosystem services—the benefits that nature provides, such as clean air, water, and wildlife habitat—has gained traction in some circles as a way to finance the conservation of these public goods. Market influences on supply and demand work in tandem to encourageecosystem protection. Jeff Kline and Trista Patterson, scientists with the Pacific Northwest (PNW) Research Station, have identified several criteria needed for ecosystem service markets to achieve their potential. These include regulatory limits on environmental damage, ecosystem services that are amenable to trading, and manageable transaction costs related to administering market programs and the necessary measuring and monitoring of marketed resources. If these criteria are not met, other conservation methods such as conservation easements, landowner incentive programs for environmental enhancement or protection, or taxes on environmental damage may be more effective. Discussions about ecosystem services often focus on increasing supply— storing more carbon or delivering more water, for example. However, net pressures on ecosystems can also be reduced by addressing consumption. Many energy efficiencies can be achieved by promoting awareness, informed choices, and behavior change. The PNW Research Station is examining both supply and demand approaches to ecosystem protection by encouraging the development of ecosystem services markets and identifying ways to reduce its own environmental footprint.
Logging Debris Matters: Better Soil, Fewer Invasive Plants
The logging debris that remains after timber harvest traditionally has been seen as a nuisance. It can make subsequent tree planting more difficult and become fuel for wildfire. It is commonly piled, burned, or taken off site. Logging debris, however, contains significant amounts of carbon and nitrogen—elements critical to soil productivity. Its physical presence in the regenerating forest creates microclimates that influence a broad range of soil and plant processes. Researchers Tim Harrington of the Pacific Northwest Research Station; Robert Slesak, a soil scientist with the Minnesota Forest Resources Council; and Stephen Schoenholtz, a professor of forest hydrology and soils at Virginia Tech, conducted a five-year study at two sites in Washington and Oregon to see how retaining logging debris affected the soil and other growing conditions at each locale. They found that keeping logging debris in place improved soil fertility, especially in areas with coarse-textured, nutrient-poor soils. Soil nitrogen and other nutrients important to tree growth increased, and soil water availability increased due to the debris’ mulching effect. The debris cooled the soil, which slowed the breakdown and release of soil carbon into the atmosphere. It also helped prevent invasive species such as Scotch broom and trailing blackberry from dominating the sites. Forest managers are using this information to help maximize the land’s productivity while reducing their costs associated with debris disposal.
Adaptation: Planning for Climate Change and Its Effects on Federal Lands
National forest managers are charged with tackling the effects of climate change on the natural resources under their care. The Forest Service National Roadmap for Responding to Climate Change and the Climate Change Performance Scorecard require managers to make significant progress in addressing climate change by 2015. To help land managers meet this challenge, Forest Service scientists conducted three case studies on national forests and adjacent national parks and documented a wide range of scientific issues and solutions. They summarized the scientific foundation for climate change adaptation and made the information accessible to land managers by creating a climate change adaptation guidebookand web portal. Case study teams discovered that collaboration among scientists and land managers is crucial to adaptation planning, as are management plans targeted to the particular ecosystem conditions and management priorities of each region. Many current management practices are consistent with climate change adaptation goals. Because timely implementation is critical, strategies are in development at the national level to speed the implementation of science-based climate change adaptation processes in national forests throughout the country.
Tangled Trends for Temperate Rain Forests as Temperatures Tick Up
Climate change is altering growing conditions in the temperate rain forest region that extends from northern California to the Gulf of Alaska. Longer, warmer growing seasons are generally increasing the overall potential for forest growth in the region. However, species differ in their ability to adapt to changing conditions. For example, researchers with Pacific Northwest Research Station examined forest trends for southeastern and southcentral Alaska and found that, in 13 years, western redcedar showed a 4.2-percent increase in live-tree biomass, while shore pine showed a 4.6-percent decrease. In general, the researchers found that the amount of live-tree biomass in extensive areas of unmanaged, higher elevation forest in southern Alaska increased by as much as 8 percent over the 13-year period, contributing to significant carbon storage. Hemlock dwarf mistletoe is another species expected to fare well under warmer conditions in Alaska. Model projections indicate that habitat for this parasitic species could increase 374 to 757 percent over the next 100 years. This could temper the prospects for western hemlock—a tree species otherwise expected to do well under future climate conditions projected for southern Alaska. In coastal forests of Washington and Oregon, water availability may be a limiting factor in future productivity, with gains at higher elevations but declines at lower elevations
Forests in Decline: Yellow-Cedar Research Yields Prototype for Climate Change Adaptation Planning
Yellow-cedar has been dying across 600 miles of North Pacific coastal rain forest—from Alaska to British Columbia—since about 1880. Thirty years ago, a small group of pathologists began investigating possible biotic causes of the decline. When no biotic cause could be found, the scope broadened into a research program that eventually encompassed the fields of ecology, soils, hydrology, ecophysiology, dendrochronology, climatology, and landscape analysis. Combined studies ultimately revealed that the loss of this culturally, economically, and ecologically valuable tree is caused by a warming climate, reduced snowpack, poor soil drainage, and the species’ shallow roots. These factors lead to fine-root freezing, which eventually kills the trees. The considerable knowledge gained while researchers sought the cause of widespread yellow-cedar mortality forms the basis for a conservation and adaptive management strategy. A new approach to mapping that overlays topography, cedar populations, soil drainage, and snow enables land managers to pinpoint locations where yellowcedar habitat is expected to be suitable or threatened in the future, thereby bringing climate change predictions into management scenarios. The research program serves as a prototype for evaluating the effects of climate change in other landscapes. It shows the value of long-term, multidisciplinary research that encourages scientists and land managers to work together toward developing adaptive management strategies
Managing Wildfire Risk in Fire-Prone Landscapes: How Are Private Landowners Contributing?
The fire-prone landscapes of the West 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. Paige Fischer and Susan Charnley, social scientists with the Pacific Northwest Research Station, surveyed private landowners in eastern Oregon to learn how they perceive fire risk on their land and what they do, if anything, to reduce that risk. The scientists found that owners who live on a forested parcel are much more likely to reduce fuels than are those who live elsewhere. Private forest owners are aware of fire risk and knowledgeable about methods for reducing fuels, but are constrained by the costs and technical challenges of protecting large acreages of forested land. Despite the collective benefits of working cooperatively, most of these owners reduce hazardous fuels on their land independently, primarily because of their distrust about working with others, and because of social norms associated with private property ownership. These results provide guidance for developing more effective fuel reduction programs that accommodate the needs and preferences of private forest landowners. The findings also indicate the potential benefits of bringing landowners into collective units to work cooperatively, raising awareness about landscape-scale fire risk, and promoting strategies for an “alllands” approach to reducing wildfire risk
DO CARBON OFFSETS WORK? THE ROLE OF FOREST MANAGEMENT IN GREENHOUSE GAS MITIGATION
As forest carbon offset projects become more popular, professional foresters are providing their expertise to support them. But when several members of the Society of American Foresters questioned the science and assumptions used to design the projects, the organization decided to convene a task force to examine whether these projects can provide the intended climate benefits.The authors emphasize the carbon-storage benefits of using wood products in place of nonrenewable, energy-intensive materials and using woodbased energy instead of fossil fuels.
Looking at the Big Picture: The Importance of Landbase Interactions Among Forests, Agriculture, and Climate Mitigation Policies
Land use change is a key part of global change. Deforestation, urban sprawl, agriculture, and other human influences have substantially altered natural ecosystems and fragmented the global landscape. Slowing down deforestation and afforesting environmentally sensitive agricultural land are important steps for mitigating climate change. Because no policy operates in a vacuum, however, it’s important to consider how separate climate mitigation policies might interact with each other. Ralph Alig, a scientist with the Pacific Northwest Research Station, and his colleagues evaluated the potential impacts of policy instruments available for climate change mitigation. By using the Forest and Agriculture Sector Optimization Greenhouse Gases model, the researchers analyzed how land might shift between forestry and agriculture and to more developed uses depending on different land use policies and several carbon pricing scenarios. They also examined the likely effects on timber, crop prices, and bioenergy production if landowners were paid to sequester carbon on their land. The researchers found that projected competition for raw materials is greatest in the short term, over the first 25 years of the 50-year projections. Climate change is occurring within a matrix of other changes. By 2050, an additional 3 billion people are expected to be living on Earth, needing food, clean water, and places to live. Incentives for landowners to maintain undeveloped land will be vital to sequestering carbon and providing other services of intact ecosystems
Tangled Trends for Temperate Rain Forests as Temperatures Tick Up
Climate change is altering growing conditions in the temperate rain forest region that extends from northern California to the Gulf of Alaska. Longer, warmer growing seasons are generally increasing the overall potential for forest growth in the region. However, species differ in their ability to adapt to changing conditions. For example, researchers with Pacific Northwest Research Station examined forest trends for southeastern and southcentral Alaska and found that, in 13 years, western redcedar showed a 4.2-percent increase in live-tree biomass, while shore pine showed a 4.6-percent decrease. In general, the researchers found that the amount of live-tree biomass in extensive areas of unmanaged, higher elevation forest in southern Alaska increased by as much as 8 percent over the 13-year period, contributing to significant carbon storage. Hemlock dwarf mistletoe is another species expected to fare well under warmer conditions in Alaska. Model projections indicate that habitat for this parasitic species could increase 374 to 757 percent over the next 100 years. This could temper the prospects for western hemlock—a tree species otherwise expected to do well under future climate conditions projected for southern Alaska. In coastal forests of Washington and Oregon, water availability may be a limiting factor in future productivity, with gains at higher elevations but declines at lower elevations.
The Role of Local Governance and Institutions in Livelihoods Adaptation to Climate Change
The most important implications of climate change from the perspective of the World Bank concern its potentially disastrous impacts on the prospects for development, especially for poorer populations in the global South. Earlier writings on climate change had tended to focus more on its links with biodiversity loss, spread of pathogens and diseases, land use planning, ecosystem change, and insurance markets, rather than its connections with development (Easterling and Apps 2005, Harvell et al. 2002, Tompkins and Adger 2004). But as the Social Development Department of the World Bank recently noted, “Climate change is the defining development challenge of our generation” (SDV, 2007: 2). These words echo the World Bank President Robert Zoellick’s statement at the United Nations Climate Change Conference in 2007 in Bali where he called climate change a “development, economic, and investment challenge.” Indeed, understanding the relationship between climate change, the human responses it necessitates, and how institutions shape such responses is an increasingly urgent need. This report directs attention towards a subset of such relationships, focusing on rural institutions and poor populations in the context of climate variability and change-induced adaptations.
Temperature control of larval dispersal and the implications for marine ecology, evolution, and conservation
Temperature controls the rate of fundamental biochemical processes and thereby regulates organismal attributes including development rate and survival. The increase in metabolic rate with temperature explains substantial among-species variation in lifehistory traits, population dynamics, and ecosystem processes. Temperature can also cause variability in metabolic rate within species. Here, we compare the effect of temperature on a key component of marine life cycles among a geographically and taxonomically diverse group of marine fish and invertebrates. Although innumerable lab studies document the negative effect of temperature on larval development time, little is known about the generality versus taxon-dependence of this relationship. We present a unified, parameterized model for the temperature dependence of larval development in marine animals. Because the duration of the larval period is known to influence larval dispersal distance and survival, changes in ocean temperature could have a direct and predictable influence on population connectivity, community structure, and regional-to-global scale patterns of biodiversity.
Politics for the day after tomorrow: The logic of apocalypse in global climate politics
The recent global climate change discourse is a prominent example of a securitization of environmental issues. While the problem is often framed in the language of existentialism, crisis or even apocalypse, climate discourses rarely result in exceptional or extraordinary measures, but rather put forth a governmental scheme of piecemeal and technocratic solutions often associated with risk management. This article argues that this seeming paradox is no accident but follows from a politics of apocalypse that combines two logics – those of security and risk – which in critical security studies are often treated as two different animals. Drawing on the hegemony theory of Ernesto Laclau and Chantal Mouffe, however, this article shows that the two are inherently connected. In the same way as the Christian pastorate could not do without apocalyptic imageries, today’s micro-politics of risk depends on a series of macro-securitizations that enable and legitimize the governmental machinery. This claim is backed up by an inquiry into current global discourses of global climate change regarding mitigation, adaptation and security implications. Although these discourses are often framed through the use of apocalyptic images, they rarely result in exceptional or extraordinary measures, but rather advance a governmental scheme of risk management. Tracing the relationship between security and risk in these discourses, we use the case of climate change to highlight the relevance of our theoretical argument.
Prolonged suppression of ecosystem carbon dioxide uptake after an anomalously warm year
Terrestrial ecosystems control carbon dioxide fluxes to and from the atmosphere1,2 through photosynthesis and respiration, a balance between net primary productivity and heterotrophic respiration, that determines whether an ecosystem issequestering carbon or releasing it to the atmosphere. Global1,3–5 and site-specific6 data sets have demonstrated that climate and climate variability influence biogeochemical processes that determine net ecosystem carbon dioxide exchange (NEE) at multiple timescales. Experimental data necessary to quantify impacts of a single climate variable, such as temperature anomalies, on NEE and carbon sequestration of ecosystems at interannual timescales have been lacking. This derives from an inability of field studies to avoid the confounding effects of natural intra-annual and interannual variability in temperature and precipitation. Here we present results from a fouryear study using replicate 12,000-kg intact tallgrass prairie monoliths located in four 184-m3 enclosed lysimeters7 . We exposed 6 of 12 monoliths to an anomalously warm year in the second year of the study8 and continuously quantified rates of ecosystem processes, including NEE. We find that warming decreases NEE in both the extreme year and the following year by inducing drought that suppresses net primary productivity in the extreme year and by stimulating heterotrophic respiration of soil biota in the subsequent year. Our data indicate thattwo years are required for NEE in the previously warmed experimental ecosystems to recover to levels measured in the control ecosystems. Thistime lag caused net ecosystem carbon sequestration in previously warmed ecosystems to be decreased threefold over the study period, compared with control ecosystems. Our findings suggest that more frequent anomalously warm years9 , a possible consequence of increasing anthropogenic carbon dioxide levels10, may lead to a sustained decrease in carbon dioxide uptake by terrestrial ecosystems. Vol 455| 18 September 2008
Aeolian process effects on vegetation communities in an arid grassland ecosystem
Many arid grassland communities are changing from grass dominance to shrub dominance, but the mechanisms involved in this conversion process are not completely understood. Aeolian processes likely contribute to this conversion from grassland to shrubland. The purpose of this research is to provide information regarding how vegetation changes occur in an arid grassland as a result of aeolian sediment transport. The experimental design included three treatment blocks, each with a 25 × 50 m area where all grasses, semi-shrubs, and perennial forbs were hand removed, a 25 × 50 m control area with no manipulation of vegetation cover, and two 10 × 25 m plots immediately downwind of the grass-removal and control areas in the prevailing wind direction, 19◦ north of east, for measuring vegetation cover. Aeolian sediment flux, soil nutrients, and soil seed bank were monitored on each treatment area and downwind plot. Grass and shrub cover were measured on each grass-removal, control, and downwind plot along continuous line transects as well as on 5 × 10 m subplots within each downwind area over four years following grass removal. On grass-removal areas, sediment flux increased significantly, soil nutrients and seed bank were depleted, and Prosopis glandulosa shrub cover increased compared to controls. Additionally, differential changes for grass and shrub cover were observed for plots downwind of vegetation-removal and control areas. Grass cover on plots downwind of vegetation-removal areas decreased over time (2004–2007) despite above average rainfall throughout the period of observation, while grass cover increased downwind of control areas; P. glandulosa cover increased on plots downwind of vegetation-removal areas, while decreasing on plots downwind of control areas. The relationships between vegetation changes and aeolian sediment flux were significant and were best described by a logarithmic function, with decreases in grass cover and increases in shrub cover occurring with small increases in aeolian sediment flux
Coupling of Vegetation Growing Season Anomalies and Fire Activity with Hemispheric and Regional-Scale Climate Patterns in Central and East Siberia
An 18-yr time series of the fraction of absorbed photosynthetically active radiation (fAPAR) taken in by the green parts of vegetation data from the NOAA Advanced Very High Resolution Radiometer (AVHRR) instrument series was analyzed for interannual variations in the start, peak, end, and length of the season of vegetation photosynthetic activity in central and east Siberia. Variations in these indicators of seasonality can give important information on interactions between the biosphere and atmosphere. A second-order local moving window regression model called the “camelback method” was developed to determine the dates of phenological events at subcontinental scale. The algorithm was validated by comparing the estimated dates to phenological field observations. Using spatial correlations with temperature and precipitation data and climatic oscillation indices, two geographically distinct mechanisms in the system of climatic controls of the biosphere in Siberia are postulated: central Siberia is controlled by an “Arctic Oscillation–temperature mechanism,” while east Siberia is controlled by an “El Niño–precipitation mechanism.” While the analysis of data from 1982 to 1991 indicates a slight increase in the length of the growing season for some land-cover types due to an earlier beginning of the growing season, the overall trend from 1982 to 1999 is toward a slightly shorter season for some land-cover types caused by an earlier end of season. The Arctic Oscillation tended toward a more positive phase in the 1980s leading to enhanced high pressure system prevalence but toward a less positive phase in the 1990s. The results suggest that the two mechanisms also control the fire regimes in central and east Siberia. Several extreme fire years in central Siberia were associated with a highly positive Arctic Oscillation phase, while several years with high fire damage in east Siberia occurred in El Niño years. An analysis of remote sensing data of forest fire partially supports this hypothesis VOLUME 20
Illuminating the Modern Dance of Climate and CO2
Records of Earth’s past climate imply higher atmospheric carbon dioxide concentrations in the future 19 SEPTEMBER 2008 VOL 321 SCIENCE
Soil Temperature following Logging-Debris Manipulation and Aspen Regrowth in Minnesota: Implications for Sampling Depth and Alteration of Soil Processes
Soil temperature is a fundamental controller of processes influencing the transformation and flux of soil C and nutrients following forest harvest. Soil temperature response to harvesting is influenced by the amount of logging debris (biomass) removal that occurs, but the duration, magnitude, and depth of influence is unclear. Logging debris manipulations (none, moderate, and heavy amounts) were applied following clearcut harvesting at four aspendominated (Populus tremuloides Michx.) sites in northeastern Minnesota, and temperature was measured at 10-, 30-, and 50-cm depths for two growing seasons. Across sites, soil temperature was significantly greater at all sample depths relative to uncut forest in some periods of each year, but the increase was reduced with increasing logging-debris retention. When logging debris was removed compared to when it was retained in the first growing season, mean growing season soil temperatures were 0.9, 1.0, and 0.8°C greater at 10-, 30-, and 50-cm depths, respectively. These patterns were also observed early in the second growing season, but there was no discernible difference among treatments later in the growing season due to the modifying effect of rapid aspen regrowth. Where vegetation establishment and growth occurs quickly, effects of logging debris removal on soil temperature and the processes influenced by it will likely be short-lived. The significant increase in soil temperature that occurred in deep soil for at least 2 yr after harvest supports an argument for deeper soil sampling than commonly occurs in experimental studies.
Climate-induced changes in the small mammal communities of the Northern Great Lakes Region
We use museum and other collection records to document large and extraordinarily rapid changes in the ranges and relative abundance of nine species of mammals in the northern Great Lakes region (white-footed mice, woodland deer mice, southern red-backed voles, woodland jumping mice, eastern chipmunks, least chipmunks, southern flying squirrels, northern flying squirrels, common opossums). These species reach either the southern or the northern limit of their distributions in this region. Changes consistently reflect increases in species of primarily southern distribution (white-footed mice, eastern chipmunks, southern flying squirrels, common opossums) and declines by northern species (woodland deer mice, southern red-backed voles, woodland jumping mice, least chipmunks, northern flying squirrels). White-footed mice and southern flying squirrels have extended their ranges over 225 km since 1980, and at particularly well-studied sites in Michigan’s Upper Peninsula, small mammal assemblages have shifted from numerical domination by northern species to domination by southern species. Repeated resampling at some sites suggests that southern species are replacing northern ones rather than simply being added to the fauna. Observed changes are consistent with predictions from climatic warming but not with predictions based on recovery from logging or changes in human populations. Because of the abundance of these focal species (the eight rodent species make up 96.5% of capture records of all forest-dwelling rodents in the region and 70% of capture records of all forest-dwelling small mammals) and the dominating ecological roles they play, these changes substantially affect the composition and structure of forest communities. They also provide an unusually clear example of change that is likely to be the result of climatic warming in communities that are experienced by large numbers of people.
Linking climate change to lemming cycles
The population cycles of rodents at northern latitudes have puzzled people for centuries1,2 , and their impact is manifest throughout the alpine ecosystem2,3 . Climate change is known to be able to drive animal population dynamics between stable and cyclic phases 4,5 , and has been suggested to cause the recent changesin cyclic dynamics of rodents and their predators 3,6–9 . But although predator–rodent interactions are commonly argued to be the cause of the Fennoscandian rodent cycles 1,10–13 , the role of the environment in the modulation of such dynamics is often poorly understood in natural systems 8,9,14 . Hence, quantitative links between climatedriven processes and rodent dynamics have so far been lacking. Here we show that winter weather and snow conditions, together with density dependence in the net population growth rate, account for the observed population dynamics of the rodent community dominated by lemmings (Lemmus lemmus) in an alpine Norwegian core habitat between 1970 and 1997, and predictthe observed absence of rodent peak years after 1994. These local rodent dynamics are coherentwith alpine bird dynamics both locally and over all ofsouthern Norway, consistent with the influence of large-scale fluctuations in winter conditions. The relationship between commonly available meteorological data and snow conditions indicates that changes in temperature and humidity, and thus conditions in the subnivean space, seem to markedly affect the dynamics of alpine rodents and their linked groups. The pattern of less regular rodent peaks, and corresponding changes in the overall dynamics of the alpine ecosystem, thusseemslikely to prevail over a growing area under projected climate change.
Impact of disturbed desert soils on duration of mountain snow cover
Snow cover duration in a seasonally snow covered mountain range (San Juan Mountains, USA) was found to be shortened by 18 to 35 days during ablation through surface shortwave radiative forcing by deposition of disturbed desert dust. Frequency of dust deposition and radiative forcing doubled when the Colorado Plateau, the dust source region, experienced intense drought (8 events and 39–59 Watts per square meter in 2006) versus a year with near normal precipitation (4 events and 17–34 Watts per square meter in 2005). It is likely that the current duration of snow cover and surface radiation budget represent a dramatic change from those before the widespread soil disturbance of the western US in the late 1800s that resulted in enhanced dust emission. Moreover, the projected increases in drought intensity and frequency and associated increases in dust emission from the desert southwest US may further reduce snow cover duration
The Historical Dynamics of Socio-ecological Traps
Environmental degradation is a typical unintended outcome of collective human behavior. Hardin’s metaphor of the ‘‘tragedy of the commons’’ has become a conceived wisdom that captures the social dynamics leading to environmental degradation. Recently, ‘‘traps’’ has gained currency as an alternative concept to explain the rigidity of social and ecological processes that produce environmental degradation and livelihood impoverishment. The trap metaphor is, however, a great deal more complex compared to Hardin’s insight. This paper takes stock of studies using the trap metaphor. It argues that the concept includes time and history in the analysis, but only as background conditions and not as a factor of causality. From a historical–sociological perspective this is remarkable since social–ecological traps are clearly path-dependent processes, which are causally produced through a conjunction of events. To prove this point the paper conceptualizes social–ecological traps as a process instead of a condition, and systematically compares history and timing in one classic and three recent studies of social– ecological traps. Based on this comparison it concludes that conjunction of social and environmental events contributes profoundly to the production of trap processes. The paper further discusses the implications of this conclusion for policy intervention and outlines how future research might generalize insights from historical–sociological studies of traps.
The influence of conversion of forest types on carbon sequestration and other ecosystem services in the South Central United States
This paper develops a forestland management model for the three states in the South Central United States (Arkansas, Louisiana, and Mississippi). Forest type and land-use shares are estimated to be a function of economic and physical variables. The results suggest that while historically pine plantations in this region have been established largely on old agricultural land, in the future pine plantations are likely to occur on converted hardwood-forest lands. This shift in the supply of land for plantations could have large effects on above-ground carbon storage and other ecosystem services. Subsidies of approximately $12–27 per ha per year would maintain the area of hardwood forests and reduce carbon emissions from the above-ground and product pool carbon stocks over the next 30 years. Across the several scenarios considered, results suggest that maintaining hardwoods could be an efficient carbon sequestration alternative.
Understanding Soil Time
Efforts to maintain soils in a sustainable manner are complicated by interactions among soil components that respond to perturbation at vastly different rates. VOL 321 SCIENCE
An Uncertain Future for Soil Carbon
Predictions of how rapidly the large amounts of carbon stored as soil organic matter will respond to warming are highly uncertain (1). Organic matter plays a key role in determining the physical and chemical properties of soils and is a major reservoir for plant nutrients. Understanding how fast organic matter in soils can be built up and lost is thus critical not just for its net effect on the atmospheric CO2 concentration but for sustaining other soil functions, such as soil fertility, on which societies and ecosystems rely. Recent analytic advances are rapidly improving our understanding of the complex and interacting factors that control the age and form of organic matter in soils, but the processes that destabilize organic matter in response to disturbances (such as warming or land use change) are poorly understood
Impact of terrestrial biosphere carbon exchanges on the anomalous CO2 increase in 2002–2003
Understanding the carbon dynamics of the terrestrial biosphere during climate fluctuations is a prerequisite for any reliable modeling of the climate-carbon cycle feedback. We drive a terrestrial vegetation model with observed climate data to show that most of the fluctuations in atmospheric CO2 are consistent with the modeled shift in the balance between carbon uptake by terrestrial plants and carbon loss through soil and plant respiration. Simulated anomalies of the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) during the last two El Nin˜o events also agree well with satellite observations. Our model results suggest that changes in net primary productivity (NPP) are mainly responsible for the observed anomalies in the atmospheric CO2 growth rate. Changes in heterotrophic respiration (Rh) mostly happen in the same direction, but with smaller amplitude. We attribute the unusual acceleration of the atmospheric CO2 growth rate during 2002–2003 to a coincidence of moderate El Nin˜o conditions in the tropics with a strong NPP decrease at northern mid latitudes, only partially compensated by decreased
Emerging Techniques for Soil Carbon measurements
Soil carbon sequestration is one approach to mitigate greenhouse gases. However, to reliably assess the quantities sequestered as well as the chemical structure of the soil carbon, new methods and equipment are needed. These methods and equipment must allow large scale measurements and the construction of dynamic maps. This paper presents results from some emerging techniques to measure carbon quantity and stability. Each methodology has specific capabilities and their combined use along with other analytical tools will improve soil organic matter research. New opportunities arise with the development and application of portable equipment, based on spectroscopic methods, as laser-induced fluorescence, laser-induced breakdown spectroscopy and near infrared, for in situ carbon measurements in different ecosystems. These apparatus could provide faster and lower cost field analyses thus improving soil carbon contents and quality databases. Improved databases are essential to model carbon balance, thus reducing the uncertainties generated through the extrapolation of limited data.
Protected Areas as Frontiers for Human Migration
Causes of human population growth near protected areas have been much debated. We conducted 821 interviews in 16 villages around Budongo Forest Reserve, Masindi district, Uganda, to explore the causes of human migration to protected areas and to identify differences in forest use between migrant and nonmigrant communities. We asked subjects for information about birthplace, migration, household assets, household activities, and forest use. Interview subjects were categorized as nonmigrants (born in one of the interview villages), socioeconomic migrants (chose to emigrate for economic or social reasons) from within Masindi district (i.e., local migrants) and from outside the Masindi district (i.e., regional migrants), or forced migrants (i.e., refugees or internally displaced individuals who emigrated as a result of conflict, human rights abuses, or natural disaster). Only 198 respondents were born in interview villages, indicating high rates of migration between 1998 and 2008. Migrants were drawn to Budongo Forest because they thought land was available (268 individuals) or had family in the area (161 individuals). A greater number of regional migrants settled in villages near Lake Albert than did forced and local migrants. Migration category was also associated with differences in sources of livelihood. Of forced migrants 40.5% earned wages through labor, whereas 25.5% of local and 14.5% of regional migrants engaged in wage labor. Migrant groups appeared to have different effects on the environment. Of respondents that hunted, 72.7% were regional migrants. Principal component analyses indicated households of regional migrants were more likely to be associated with deforestation. Our results revealed gaps in current models of human population growth around protected areas. By highlighting the importance of social networks and livelihood choices, our results contribute to a more nuanced understanding of causes of migration and of the environmental effects of different migrant groups. Conservation Biology, Volume 26, No. 3, 547–556
Barking up the Wrong Tree? Forest Sustainability in the wake of Emerging Bioenergy Policies
The spotted owl controversy revealed that federal forest management policies alone could not guarantee functioning forest ecosystems. At the same time as the owl’s listing, agreements made at the 1992 Rio Earth Summit highlighted the mounting pressures on natural systems, thus unofficially marking the advent of sustainable forestry management (SFM).2 While threats to forest ecosystems from traditional logging practices certainly remain,3 developed and developing countries have shifted generally toward more sustainable forest management, at least on paper, including codifying various sustainability indicators in public laws.4 Nevertheless, dark policy clouds are gathering on the forest management horizon. Scientific consensus has grown in recent years around a new and arguably more onerous threat to all of the world’s ecosystems—climate change. Governments’ responses have focused on bioenergy policies aimed at curtailing anthropogenic greenhouse gas (GHG) emissions, and mandatesfor renewables in energy supplies now abound worldwide. [Vol. 37:000
