CFE agenda 091117 - Laserfiche WebLink

Browse Search

climatic gradients and move into new areas of suit- able habitat. In addition, current reserve networks, many of which protect only a small, potentially biased samples of environmental conditions across the range of an individual species or habitat type, are likely to become increasingly less representa- tive under combined impacts of climate change and habitat loss (Dyke 2004). The negative consequences of expanding urban development on species and habitats are well estab- lished (e.g., Chace and Walsh 2006, Hansen et al. 2005, McKinney 2002). Direct habitat loss, habi- tat fragmentation, and isolation can pose signifi- cant threats to population viability on their own. However, interactions between climate change and other drivers, such as land use change, may have greater impacts on biodiversity than any one driver alone (Brook et al. 2008). In a survey of 248 papers from the climate change literature that addressed the conservation and management of biodiversity or ecosystems, Felton et al. (2009) found that fewer than half of the studies addressed climate change in rela- tion to other anthropogenic threats. Recent reviews emphasize that the lack of integration of climate change impacts with other synergistic threats is likely to inadequately capture future impacts on biodiver- sity (Brook et al. 2008, de Chazal and Rounsevell 2009). For example, Warren et al. (2001) exam- ined responses of 46 species of butterflies that were expected to expand their ranges as a result of climate warming over the last 30 years, and found that three - quarters had declined as a result of habitat loss, with sedentary species and habitat specialists among the most adversely affected. Jetz et al. (2007) estimated that globally 10 - 20% of land bird species would be imperiled by climate change and land conversion by 2100, but that differences in species diversity and range will affect the relative influence of these driv- ers. For example, they suggest that climate change will be the principal driver of range contractions at higher latitudes, while land conversion will be the principal driver of species range contractions in the tropics (Jett et al. 2007). However, their analysis did not examine the potential for range shifts (in addi- tion to contractions) to occur as a result of climate change. Projections of species range shifts under climate change often assume that species distributions are limited primarily by temperature without account- ing for the spatial configuration of the landscape or habitat. To address this issue, some authors have attempted to integrate a metapopulation dynam- ics framework with broader scale changes in species ranges. Opdam and Washer (2004) characterize range shifts as the result of extinction of (meta) popu- lations at the warm range limit and colonization into regions that have transitioned into suitable thermal conditions at the cooler end of the range. The ability of a species to shift into more suitable areas will be a function of new climate conditions (e.g. tempera- ture) and extreme weather conditions. However, the authors suggest that some species metapopulations will be unable to persist in areas where fragmenta- tion has severely degraded habitat quality and patch availabilty, and will likely exhibit range contractions ( Opdam and Washer 2004). Modeling work has produced similar results, indicating that extinction thresholds are lower under the combined effects of habitat fragmentation and climate change (Travis 2003). Mclnery et al. (2007) further demonstrated that the effect of habitat fragmentation on range shifts may be dependent on species dispersal charac- teristics and populations dynamics during periods of climate change. Their model suggests that range shifts are more successful in less fragmented (clumped) landscapes for species with low colonization rates. However, for species with especially strong disper- sal and colonization abilities, fragmentation could have the opposite effect, facilitating range shifts so long as the availability of suitable habitat keeps pace with climatic shifts on the landscape (Mclnerny et al. 2007).