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Insect Responses to Major Landscape-Level Disturbance
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Keywords
tolerance, dispersal, succession, local extinction, outbreak, population dynamics
Abstract
Disturbances are abrupt events that dramatically alter habitat conditions and resource distribution for populations and communities. Terrestrial land- scapes are subject to various disturbance events that create a matrix of patches with different histories of disturbance and recovery. Species tolerances to ex- treme conditions during disturbance or to altered habitat or resource condi- tions following disturbances determine responses to disturbance. Intolerant populations may become locally extinct, whereas other species respond posi- tively to the creation of new habitat or resource conditions. Local extinction represents a challenge for conservation biologists. On the other hand, out- breaks of herbivorous species often are triggered by abundant or stressed hosts and relaxation of predation following disturbances. These insect re- sponses can cause further changes in ecosystem conditions and predispose communities to future disturbances. Improved understanding of insect re- sponses to disturbance will improve prediction of population and community dynamics, as well as ecosystem and global changes.
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The Rescaling of Global Environmental Politics
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Key Words
governance, international, linked issues, networks, scale
Abstract
In the past half-century, the practice and study of global environmental politics and governance have been dramatically rescaled. They have be- come increasingly complex and interconnected with respect to the level (between local and global) at which they take place, the range of actors engaged in them, and the linkages between them and nominally nonen- vironmental issues. Global environmental politics and governance have been rescaled vertically down toward provincial and municipal gov- ernments and up toward supranational regimes. They have also been rescaled horizontally across regional and sectoral organizations and net- works and across new issues, such as development, security, and trade among others. This rescaling reflects shifts in the magnitude, complexity, and interconnectedness of the global environmental problems humans face as well as epistemological shifts in how humans understand and respond to these problems, and rescaling has implications for both the practice and study of global environmental politics.
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20th-Century doubling in dust archived in an Antarctic Peninsula ice core parallels climate change and desertification in South America
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Crustal dust in the atmosphere impacts Earth’s radiative forcing directly by modifying the radiation budget and affecting cloud nucleation and optical properties, and indirectly through ocean fertilization, which alters carbon sequestration. Increased dust in the atmosphere has been linked to decreased global air tempera- ture in past ice core studies of glacial to interglacial transitions. We present a continuous ice core record of aluminum deposition during recent centuries in the northern Antarctic Peninsula, the most rapidly warming region of the Southern Hemisphere; such a record has not been reported previously. This record shows that aluminosilicate dust deposition more than doubled during the 20th century, coincident with the 1°C Southern Hemisphere warming: a pattern in parallel with increasing air temperatures, decreasing relative humidity, and widespread desertification in Patagonia and northern Argentina. These results have far-reaching implications for understanding the forces driving dust generation and impacts of changing dust levels on climate both in the recent past and future.
aluminosilicate dust global warming human impacts Patagonia radiative transfer
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HOW LONG HAVE WE BEEN IN THE ANTHROPOCENE ERA?
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Editorial- 1st paragraph: With great interest we have read Ruddiman’s intriguing article which is in favor of placing the start of the Anthropocene at 5–8 millennia BP instead of the late quarter of the 18th century. He shows how land exploitation for agriculture and animal husbandry may have led to enhanced emissions of CO2 and CH4 to the atmosphere, thereby modifying the expected changes in the concentrations of these gases beyond those expected from variations in the Milankovich orbital parameters. Much of his argument depends on the correctness of their projected CH4 concen- tration curve from 7,000 years BP to pre-industrial times showing a decline to about 425 ppb, according to Milankovich, instead of the measured 700 ppb. It appears, however, strange that in Ruddiman’s analysis the proposed increase of CH4 due to anthropogenic activities stopped at about 1000 years BP, because ice core data showed almost constant mixing ratios of CH4 between 1000 years BP and about 200 years ago before the rapid rise of CH4 in the industrial period (IPCC, 2001). A major feature of Ruddiman’s argument is that natural atmospheric CH4 concentrations depend strongly on geological varying summer time insolations in the tropical northern hemisphere, controlling tropical wetlands and methane release from decaying organic matter under anaerobic conditions.
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Turning back from the brink: Detecting an impending regime shift in time to avert it
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Ecological regime shifts are large, abrupt, long-lasting changes in ecosystems that often have considerable impacts on human econ- omies and societies. Avoiding unintentional regime shifts is widely regarded as desirable, but prediction of ecological regime shifts is notoriously difficult. Recent research indicates that changes in ecological time series (e.g., increased variability and autocorrela- tion) could potentially serve as early warning indicators of im- pending shifts. A critical question, however, is whether such indicators provide sufficient warning to adapt management to avert regime shifts. We examine this question using a fisheries model, with regime shifts driven by angling (amenable to rapid reduction) or shoreline development (only gradual restoration is possible). The model represents key features of a broad class of ecological regime shifts. We find that if drivers can only be manipulated gradually management action is needed substantially before a regime shift to avert it; if drivers can be rapidly altered aversive action may be delayed until a shift is underway. Large increases in the indicators only occur once a regime shift is initiated, often too late for management to avert a shift. To improve usefulness in averting regime shifts, we suggest that research focus on defining critical indicator levels rather than detecting change in the indicators. Ideally, critical indicator levels should be related to switches in ecosystem attractors; we present a new spectral density ratio indicator to this end. Averting ecological regime shifts is also dependent on developing policy pro- cesses that enable society to respond more rapidly to information about impending regime shifts.
early warning indicator ecological threshold spectral density ratio
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The millennial atmospheric lifetime of anthropogenic CO2
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The notion is pervasive in the climate science community and in the public at large that the climate impacts of fossil fuel CO2 release will only persist for a few centuries. This conclusion has no basis in theory or models of the atmosphere/ocean carbon cycle, which we review here. The largest fraction of the CO2 recovery will take place on time scales of centuries, as CO2 invades the ocean, but a significant fraction of the fossil fuel CO2, ranging in published models in the literature from 20–60%, remains airborne for a thousand years or longer. Ultimate recovery takes place on time scales of hundreds of thousands of years, a geologic longevity typically associated in public perceptions with nuclear waste. The glacial/interglacial climate cycles demonstrate that ice sheets and sea level respond dramatically to millennial-timescale changes in climate forcing. There are also potential positive feedbacks in the carbon cycle, including methane hydrates in the ocean, and peat frozen in permafrost, that are most sensitive to the long tail of the fossil fuel CO2 in the atmosphere.
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TUNDRA’S BURNING
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More than 20,000 lightning strikes were recorded on the North Slope of Alaska in 2007. Some struck the vast stretches of lakes; some hit the
treeless tundra. And one of them torched into life the largest and longest-lasting tundra fire recorded in the state’s history. The blaze, which started near the Anaktuvuk River on 16 July, burned 7,000 hectares a day at its peak, and eventually consumed 100,000 hectares, an area larger than that of New York City. It finally stopped burning in early October, smothered by thick snow. Arctic lightning fire
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Environment, vegetation and greenness (NDVI) along the North America and Eurasia Arctic transects
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Satellite-based measurements of the normalized difference vegetation index (NDVI; an index of vegetation greenness and photosynthetic capacity) indicate that tundra environments are generally greening and becoming more productive as climates warm in the Arctic. The greening, however, varies and is even negative in some parts of the Arctic. To help interpret the space-based observations, the International Polar Year (IPY) Greening of the Arctic project conducted ground-based surveys along two >1500 km transects that span all five Arctic bioclimate subzones. Here we summarize the climate, soil, vegetation, biomass, and spectral information collected from the North America Arctic transect (NAAT), which has a more continental climate, and the Eurasia Arctic transect (EAT), which has a more oceanic climate. The transects have broadly similar summer temperature regimes and overall vegetation physiognomy, but strong differences in precipitation, especially winter precipitation, soil texture and pH, disturbance regimes, and plant species composition and structure. The results indicate that summer warmth and NDVI increased more strongly along the more continental transect.
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Late Pleistocene California droughts during deglaciation and Arctic warming
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Recent studies document the synchronous nature of shifts in North Atlantic regional climate, the intensity of the East Asian monsoon, and productivity and precipitation in the Cariaco Basin during the last glacial and deglacial period. Yet questions remain as to what climate mechanisms influenced continental regions far removed from the North Atlantic and beyond the direct influence of the inter-tropical convergence zone. Here, we present U-series calibrated stable isotopic and trace element time series for a speleothem from Moaning Cave on the western slope of the central Sierra Nevada, California that documents changes in precipitation that are approximately coeval with Greenland temperature changes for the period 16.5 to 8.8 ka. From 16.5 to 10.6 ka, the Moaning Cave stalagmite proxies record drier and possibly warmer conditions, signified by elevated à18O, à13C, [Mg], [Sr], and [Ba] and more radiogenic 87Sr/86Sr, during Northern Hemisphere warm periods (Bølling, early and late Allerød) and wetter and possibly colder conditions during Northern Hemisphere cool periods (Older Dryas, Inter-Allerød Cold Period, and Younger Dryas). Moaning Cave stable isotope records indicate that wet conditions persisted in this area well beyond 11.5 ka, suggesting the effects of the Younger Dryas event may have been longer lived in the western Sierra Nevada than in Greenland. However, a shifting drip center and corresponding change in seepage water routing may have influenced the trace element records between 10.6 and 9.6 ka. Linkages between northern high-latitude climate and precipitation in the Sierra Nevada suggested here could indicate that, under conditions of continued global warming, this drought-prone region may experience a reduction in Pacific-sourced moisture.
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Disappearing Arctic sea ice reduces available water in the American west
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Recent decreases in Arctic sea ice cover and the probability of continued decreases have raised the question of how reduced Arctic sea ice cover will influence extrapolar climate. Using a fully coupled earth system model, we generate one possible future Arctic sea ice distribution. We use this ‘‘future’’ sea ice distribution and the corresponding sea surface temperatures (SSTs) to run a fixed SST and ice concentration experiment with the goal of determining direct climate responses to the reduction in Arctic sea ice that is projected to occur in the next 50 years. Our results indicate that future reductions in Arctic sea ice cover could significantly reduce available water in the American west and highlight the fact that the most severe impacts of future climate change will likely be at a regional scale.
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