-
Biodiversity loss and its impact on humanity
-
The most unique feature of Earth is the existence of life, and the most extraordinary feature of life is its diversity. Approximately 9 million types of plants, animals, protists and fungi inhabit the Earth. So, too, do 7 billion people. Two decades ago, at the first Earth Summit, the vast majority of the world’s nations declared that human actions were dismantling the Earth’s ecosystems, eliminating genes, species and biological traits at an alarming rate. This observation led to the question of how such loss of biological diversity will alter the functioning of ecosystems and their ability to provide society with the goods and services needed to prosper.
Located in
Resources
/
Climate Science Documents
-
A large source of low-volatility secondary organic aerosol
-
Forests emit large quantities of volatile organic compounds (VOCs) to the atmosphere. Their condensable oxidation products can form secondary organic aerosol, a significant and ubiquitous component of atmospheric aerosol 1,2, which is known to affect the Earth’s radiation balance by scattering solar radiation and by acting as cloud condensation nuclei 3. The quantitative assessment of such climate effects remains hampered by a number of factors, including an incom- plete understanding of how biogenic VOCs contribute to the formation of atmospheric secondary organic aerosol. The growth of newly formed particles from sizes of less than three nanometres up to the sizes of cloud condensation nuclei (about one hundred nanometres) in many continental ecosystems requires abundant, essentially non- volatile organic vapours4–6, but the sources and compositions of such vapours remain unknown. Here we investigate the oxidation of VOCs, in particular the terpene a-pinene, under atmospherically relevant conditions in chamber experiments. We find that a direct pathway leads from several biogenic VOCs, such as monoterpenes, to the for- mation of large amounts of extremely low-volatility vapours. These vapours form at significant mass yield in the gas phase and condense irreversibly onto aerosol surfaces to produce secondary organic aero- sol, helping to explain the discrepancy between the observed atmo- spheric burden of secondary organic aerosol and that reported by many model studies2. We further demonstrate how these low-volatility vapours can enhance, or even dominate, the formation and growth of aerosol particles over forested regions, providing a missing link between biogenic VOCs and their conversion to aerosol particles. Our findings could help to improve assessments of biosphere–aerosol– climate feedback mechanisms 6–8, and the air quality and climate effects of biogenic emissions generally.
Located in
Resources
/
Climate Science Documents
-
Coastal habitats shield people and property from sea-level rise and storms
-
Extreme weather, sea-level rise and degraded coastal ecosystems are placing people and property at greater risk of damage from coastal hazards 1–5. The likelihood and magnitude of losses may be reduced by intact reefs and coastal vegetation 1, especially when those habitats fringe vulnerable communities and infrastructure. Using five sea-level-rise scenarios, we calculate a hazard index for every 1 km2 of the United States coastline. We use this index to identify the most vulnerable people and property as indicated by being in the upper quartile of hazard for the nation’s coastline. The number of people, poor families, elderly and total value of residential property that are most exposed to hazards can be reduced by half if existing coastal habitats remain fully intact. Coastal habitats defend the greatest number of people and total property value in Florida, New York and California. Our analyses deliver the first national map of risk reduction owing to natural habitats and indicates where conservation and restoration of reefs and vegetation have the greatest potential to protect coastal communities.
Located in
Resources
/
Climate Science Documents
-
Basic mechanism for abrupt monsoon transitions
-
Monsoon systems influence the livelihood of hundreds of millions of people. During the Holocene and last glacial period, rainfall in India and China has undergone strong and abrupt changes. Though details of monsoon circulations are complicated, observations reveal a defining moisture-advection feedback that dominates the seasonal heat balance and might act as an internal amplifier, leading to abrupt changes in response to relatively weak external perturbations. Here we present a minimal conceptual model capturing this positive feedback. The basic equations, motivated by observed relations, yield a threshold behavior, robust with respect to addition of other physical processes. Below this threshold in net radiative influx, Rc , no conventional monsoon can develop; above Rc , two stable regimes exist. We identify a nondimensional para- meter l that defines the threshold and makes monsoon systems comparable with respect to the character of their abrupt transition. This dynamic similitude may be helpful in understanding past and future variations in monsoon circulation. Within the restrictions of the model, we compute Rc for current monsoon systems in India, China, the Bay of Bengal, West Africa, North America, and Australia, where moisture advection is the main driver of the circulation.
Earth system | tipping element | abrupt climate change | atmospheric circulation | nonlinear dynamics
Located in
Resources
/
Climate Science Documents
-
Evolutionary history and the effect of biodiversity on plant productivity
-
Loss of biological diversity because of extinction is one of the most pronounced changes to the global environment. For several decades, researchers have tried to understand how changes in biodiversity might impact biomass production by examining how biomass correlates with a number of biodiversity metrics (especially the number of species and functional groups). This body of research has focused on species with the implicit assumption that they are independent entities. However, functional and ecological similarities are shaped by patterns of common ancestry, such that distantly related species might contribute more to production than close relatives, perhaps by increasing niche breadth. Here, we analyze 2 decades of experiments performed in grassland ecosystems throughout the world and examine whether the evolutionary relationships among the species comprising a community predict how biodiversity impacts plant biomass production. We show that the amount of phylogenetic diversity within communities explained significantly more variation in plant community biomass than other measures of diversity, such as the number of species or functional groups. Our results reveal how evolutionary history can provide critical information for understanding, predicting, and potentially ameliorating the effects of biodiversity loss and should serve as an impetus for new biodiversity experiments.
Located in
Resources
/
Climate Science Documents
-
Ecosystem services: From theory to implementation
-
Around the world, leaders are increasingly recognizing ecosystems as natural capital assets that supply life-support services of tremendous value. The challenge is to turn this recognition into incentives and institutions that will guide wise investments in natural capital, on a large scale. Advances are required on three key fronts, each featured here: the science of ecosystem production functions and service mapping; the design of appropriate finance, policy, and governance systems; and the art of implementing these in diverse biophysical and social contexts. Scientific understanding of ecosystem production functions is improving rapidly but remains a limiting factor in incorporating natural capital into decisions, via systems of national accounting and other mechanisms. Novel institutional structures are being established for a broad array of services and places, creating a need and opportunity for systematic assessment of their scope and limitations. Finally, it is clear that formal sharing of experience, and defining of priorities for future work, could greatly accelerate the rate of innova- tion and uptake of new approaches.
Located in
Resources
/
Climate Science Documents
-
Biotic Drivers of Stream Planform: Implications for Understanding the Past and Restoring the Future
-
Traditionally, stream channel planform has been viewed as a function of larger watershed and valley-scale physical variables, including valley slope, the amount of discharge, and sediment size and load. Biotic processes serve a crucial role in transforming channel planform among straight, braided, meandering, and anabranching styles by increasing stream-bank stability and the probability of avulsions, creating stable multithread (anabranching) channels, and affecting sedimentation dynamics. We review the role of riparian vegetation and channel-spanning obstructions—beaver dams and logjams—in altering channel–floodplain dynamics in the southern Rocky Mountains, and we present channel planform scenarios for combinations of vegetation and beaver populations or old-growth forest that control logjam formation. These conceptual models provide understanding of historical planform variability throughout the Holocene and outline the implications for stream restoration or management in broad, low-gradient headwater valleys, which are important for storing sediment, carbon, and nutrients and for supporting a diverse riparian community.
Keywords: stream planform, riparian vegetation, beaver, old-growth forest, restoration
Located in
Resources
/
Climate Science Documents
-
Diverse pollinator communities enhance plant reproductive success
-
Understanding the functional consequences of biodiversity loss is a major goal of ecology. Animal-mediated pollination is an essential ecosystem function and service provided to mankind. However, little is known how pollinator diversity could affect pollination services. Using a substitutive design, we experimentally manipu- lated functional group (FG) and species richness of pollinator communities to investigate their consequences on the reproductive success of an obligate out-crossing model plant species, Raphanus sativus. Both fruit and seed set increased with pollinator FG richness. Furthermore, seed set increased with species richness in pol- linator communities composed of a single FG. However, in multiple-FG communities, highest species richness resulted in slightly reduced pollination services compared with intermediate species richness. Our analysis indicates that the presence of social bees, which showed roughly four times higher visitation rates than solitary bees or hoverflies, was an important factor contributing to the positive pollinator diversity–pollination service relationship, in particular, for fruit set. Visitation rate at different daytimes, and less so among flower heights, varied among social bees, solitary bees and hoverflies, indicating a niche complementarity among these pollinator groups. Our study demonstrates enhanced pollination services of diverse pollinator communities at the plant population level and suggests that both the niche complementarity and the presence of specific taxa in a pollinator community drive this positive relationship.
Located in
Resources
/
Climate Science Documents
-
Can a collapse of global civilization be avoided?
-
Environmental problems have contributed to numerous collapses of civilizations in the past. ... But today, for the first time, humanity’s global civilization—the worldwide,increasingly interconnected, highly technological society in which we all are to one degree or another, embedded—is threatened with collapse by an array of
environmental problems. Humankind finds itself engaged in what Prince Charles described as ‘an act of suicide on a grand scale’ [4], facing what the UK’s Chief Scientific Advisor John Beddington called a ‘perfect storm’ of environmental problems [5]. The most serious of these problems show signsof rapidly escalating severity, especially climate disruption.
Located in
Resources
/
Climate Science Documents
-
Climate Change and Existing Law: A Survey of Legal Issues Past, Present, and Future
-
Summary: This report surveys existing law for legal issues that have arisen, or may arise in the future, on account of climate change and government responses thereto. At the threshold of many climate-change-related lawsuits are two barriers—whether the plaintiff has standing to sue and whether the claim being made presents a political question. Both barriers have forced courts to apply amorphous standards in a new and complex context. Efforts to mitigate climate change—that is, reduce greenhouse gas (GHG) emissions—have spawned a host of legal issues. The Supreme Court resolved a big one in 2007: the Clean Air Act (CAA), it said, authorizes EPA to regulate GHG emissions. EPA’s subsequent efforts to carry out that authority have been sustained by the D.C. Circuit. Another issue is whether EPA’s “endangerment finding” for GHG emissions from new motor vehicles will compel EPA to move against GHG emissions from other sources, and, if EPA does, whether the CAA authorizes cap- and-trade programs. Still other mitigation issues are (1) the role of the Endangered Species Act in addressing climate change; (2) how climate change must be considered under the National Environmental Policy Act; (3) liability and other questions raised by carbon capture and sequestration; (4) constitutional constraints on land use regulation and state actions to control GHG emissions; and (5) whether the public trust doctrine applies to the atmosphere. Liability for harms allegedly caused by climate change has raised another crop of legal issues. The Supreme Court decision that the CAA bars federal judges from imposing their own limits on GHG emissions from power plants has led observers to ask: Can plaintiffs alleging climate change harms still seek monetary damages, and are state law claims still allowed? The two rulings so far say no to the former, but split on the latter. Questions of insurance policy coverage are also likely to be litigated. Finally, the applicability of international law principles to climate change has yet to be resolved.Water shortages thought to be induced by climate change likely will lead to litigation over the nature of water rights. Shortages have already prompted several lawsuits over whether cutbacks in water delivered from federal projects effect Fifth Amendment takings or breaches of contract. Sea level rise and extreme precipitation linked to climate change raise questions as to (1) the effect of sea level rise on the beachfront owner’s property line; (2) whether public beach access easements migrate with the landward movement of beaches; (3) design and operation of federal levees; and (4) government failure to take preventive measures against climate change harms. Other adaptation responses to climate change raising legal issues, often property rights related, are beach armoring (seawalls, bulkheads, etc.), beach renourishment, and “retreat” measures. Retreat measures seek to move existing development away from areas likely to be affected by floods and sea level rise, and to discourage new development there.
Natural disasters to which climate change contributes may prompt questions as to whether response actions taken in an emergency are subject to relaxed requirements and, similarly, as to the rebuilding of structures destroyed by such disasters just as they were before. Finally, immigration and refugee law appear not to cover persons forced to relocate because of climate change impacts such as drought or sea level rise.
Located in
Resources
/
Climate Science Documents
