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Atlantic hurricanes and climate over the past 1,500 years
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Atlantic tropical cyclone activity, as measured by annual storm counts, reached anomalous levels over the past decade1. The short nature of the historical record and potential issues with its reliability in earlier decades, however, has prompted an ongoing debate regarding the reality and significance of the recent rise2–5. Here we place recent activity in a longer-term context by comparing two independent estimates of tropical cyclone activity over the past 1,500 years. The first estimate is based on a composite of regional sedimentary evidence of landfalling hurricanes, while the second estimate uses a previously published statistical model of Atlantic tropical cyclone activity driven by proxy reconstructions of past climate changes. Both approaches yield consistent evidence of a peak in Atlantic tropical cyclone activity during medieval times (around AD 1000) followed by a subsequent lull in activity. The statistical model indicates that the medieval peak, which rivals or even exceeds (within uncertainties) recent levels of activity, results from the reinforcing effects of La-Nina-like climate conditions and relative tropical Atlantic warmth.
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Beaver (Castor canadensis) mitigate the effects of climate on the area of open water in boreal wetlands in western Canada
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Shallow open water wetlands provide critical habitat for numerous species, yet they have become increasingly vulnerable to drought and warming temperatures and are often reduced in size and depth or disappear during drought. We examined how temperature, precipitation and beaver (Castor canadensis) activity influenced the area of open water in wetlands over a 54- year period in the mixed-wood boreal region of east-central Alberta, Canada. This entire glacial landscape with intermittently connected drainage patterns and shallow wetland lakes with few streams lost all beaver in the 19th century, with beaver returning to the study area in 1954. We assessed the area of open water in wetlands using 12 aerial photo mosaics from 1948 to 2002, which covered wet and dry periods, when beaver were absent on the landscape to a time when they had become well established. The number of active beaver lodges explained over 80% of the variability in the area of open water during that period. Temperature, precipitation and climatic variables were much less important than beaver in maintaining open water areas. In addition, during wet and dry years, the presence of beaver was associated with a 9-fold increase in open water area when compared to a period when beaver were absent from those same sites. Thus, beaver have a dramatic influence on the creation and maintenance of wetlands even during extreme drought. Given the important role of bea- ver in wetland preservation and in light of a drying climate in this region, their removal should be considered a wetland disturbance that should be avoided.
Beaver
Castor canadensis
Drought East-central Alberta Elk Island National Park Mixed-wood boreal Wetland conservation
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Effective Enforcement in a Conservation Area
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There are two primary approaches to wildlife conservation, the generation of economic benefits from wildlife to local communities, so that protecting wildlife is in their interest, and the enforcement of protected areas. Outside of protected areas, community- based conservation must be the cornerstone of protection (1). However, within protected areas there is debate as to whether enforcement can maintain wildlife and even whether protected areas as wildlife reserves are realistic or morally justified (2). Here, we present the history of illegal harvesting in Serengeti National Park (SNP), Tanzania; estimate the amount of antipoaching activity by park staff; and show how the level of funding for antipoaching has affected the trends in abundance of three severely affected species: African buffalo, elephant, and black rhino.
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Biophysical and Biogeochemical Responses to Climate Change Depend on Dispersal and Migration
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Different species, populations, and individuals disperse and migrate at different rates. The rate of movement that occurs in response to changes in climate, whether fast or slow, will shape the distribution of natural ecosystems in the decades to come. Moreover, land-use patterns associated with urban, suburban, rural, and agricultural development will complicate ecosystem adaptation to climate change by hindering migration. Here we examine how vegetation’s capacity to disperse and migrate may affect the biophysical and biogeochemical characteristics of the land surface under anthropogenic climate change. We demonstrate that the effectiveness of plant migration strongly influences carbon storage, evapotranspiration, and the absorption of solar radiation by the land surface. As a result, plant migration affects the magnitude, and in some cases the sign, of feedbacks from the land surface to the climate system. We conclude that future climate projections depend on much better understanding of and accounting for dispersal and migration.
Keywords: vegetation–climate feedback, global change, carbon storage, evapotranspiration, surface radiation
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Detection and Attribution of Streamflow Timing Changes to Climate Change in the Western United States
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This article applies formal detection and attribution techniques to investigate the nature of observed shifts in the timing of streamflow in the western United States. Previous studies have shown that the snow hy- drology of the western United States has changed in the second half of the twentieth century. Such changes manifest themselves in the form of more rain and less snow, in reductions in the snow water contents, and in earlier snowmelt and associated advances in streamflow ‘‘center’’ timing (the day in the ‘‘water-year’’ on average when half the water-year flow at a point has passed). However, with one exception over a more limited domain, no other study has attempted to formally attribute these changes to anthropogenic increases of greenhouse gases in the atmosphere. Using the observations together with a set of global climate model simulations and a hydrologic model (applied to three major hydrological regions of the western United States—the California region, the upper Colorado River basin, and the Columbia River basin), it is found that the observed trends toward earlier ‘‘center’’ timing of snowmelt-driven streamflows in the western United States since 1950 are detectably different from natural variability (significant at the p , 0.05 level). Furthermore, the nonnatural parts of these changes can be attributed confidently to climate changes induced by anthropogenic greenhouse gases, aerosols, ozone, and land use. The signal from the Columbia dominates the analysis, and it is the only basin that showed a detectable signal when the analysis was performed on individual basins. It should be noted that although climate change is an important signal, other climatic processes have also contributed to the hydrologic variability of large basins in the western United States.
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ECONOMICS IN A FULL WORLD
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The global economy is now so large that society can no longer safely pretend it operates within a limitless ecosystem. Developing an economy that can be sustained within the finite biosphere requires new ways of thinking
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Extent and scale of local adaptation in salmonid fishes: review and meta-analysis
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What is the extent and scale of local adaptation (LA)? How quickly does LA arise? And what is its underlying molecular basis? Our review and meta-analysis on salmonid fishes estimates the frequency of LA to be B55–70%, with local populations having a 1.2 times average fitness advantage relative to foreign populations or to their perfor- mance in new environments. Salmonid LA is evident at a variety of spatial scales (for example, few km to41000 km) and can manifest itself quickly (6–30 generations). As the geographic scale between populations increases, LA is generally more frequent and stronger. Yet the extent of LA in salmonids does not appear to differ from that in other assessed taxa. Moreover, the frequency with which foreign salmonid populations outperform local populations (B23– 35%) suggests that drift, gene flow and plasticity often limit or mediate LA. The relatively few studies based on candidate gene and genomewide analyses have identified footprints of selection at both small and large geographical scales, likely reflecting the specific functional properties of loci and the associated selection regimes (for example, local niche partitioning, pathogens, parasites, photoperiodicity and seasonal timing). The molecular basis of LA in salmonids is still largely unknown, but differential expression at the same few genes is implicated in the convergent evolution of certain phenotypes. Collectively, future research will benefit from an integration of classical and molecular approaches to understand: (i) species differences and how they originate, (ii) variation in adaptation across scales, life stages, population sizes and environmental gradients, and (iii) evolutionary responses to human activities.
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Biodiversity management in the face of climate change: A review of 22 years of recommendations
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Climate change creates new challenges for biodiversity conservation. Species ranges and ecological dynamics are already responding to recent climate shifts, and current reserves will not continue to support all species they were designed to protect. These problems are exacerbated by other global changes. Scholarly articles recommending measures to adapt conservation to climate change have proliferated over the last 22 years. We systematically reviewed this literature to explore what potential solutions it has identified and what consensus and direction it provides to cope with climate change. Several consistent recommendations emerge for action at diverse spatial scales, requiring leadership by diverse actors. Broadly, adaptation requires improved regional institutional coordination, expanded spatial and temporal perspective, incorporation of climate change scenarios into all planning and action, and greater effort to address multiple threats and global change drivers simultaneously in ways that are responsive to and inclusive of human communities. However, in the case of many recommendations the how, by whom, and under what conditions they can be implemented is not specified. We synthesize recommendations with respect to three likely conservation pathways: regional planning; site-scale management; and modification of existing conservation plans. We identify major gaps, including the need for (1) more specific, operational examples of adaptation principles that are consistent with unavoidable uncertainty about the future; (2) a practical adaptation planning process to guide selection and integration of recommendations into existing policies and programs; and (3) greater integration of social science into an endeavor that, although dominated by ecology, increasingly recommends extension beyond reserves and into human-occupied landscapes.
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Carbon Dynamics of the Forest Sector
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Main points: The basic ecosystem science behind carbon dynamics in forests is relatively straightforward (really!).This science doesn’t seem to be applied very routinely in the policy arena. This mismatch is undermining the potential of the forest sector in helping to mitigate greenhouse gases in the atmosphere
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Assessing potential climate change effects on vegetation using a linked model approach
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We developed a process that links the mechanistic power of dynamic global vegetation models with the detailed vegetation dynamics of state-and-transition models to project local vegetation shifts driven by projected climate change. We applied our approach to central Oregon (USA) ecosystems using three climate change scenarios to assess potential future changes in species composition and community structure. Our results suggest that: (1) legacy effects incorporated in state-and-transition models realistically dampen climate change effects on vegetation; (2) species-specific response to fire built into state-and- transition models can result in increased resistance to climate change, as was the case for ponderosa pine (Pinus ponderosa) forests, or increased sensitivity to climate change, as was the case for some shrublands and grasslands in the study area; and (3) vegetation could remain relatively stable in the short term, then shift rapidly as a consequence of increased disturbance such as wildfire and altered environmental conditions. Managers and other land stewards can use results from our linked models to better anticipate potential climate-induced shifts in local vegetation and resulting effects on wildlife habitat.
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