|
to simulate the dynamic changes expected to occur
<br />at a smaller scale as the global climate changes; they
<br />are also expensive to run and data - storage intensive
<br />(K. Hayhoe et al. 2010). The regional model simu-
<br />lations generated by the North American Regional
<br />Climate Change Assessment Program ( NARCCAP)
<br />are currently the most comprehensive set of region-
<br />al models currently available ( NARCCAP 2007).
<br />The NARCCAP uses regional model /global model
<br />pairs to simulate conditions from 2041 to 2070 and
<br />compared to 1971 -2000 (K. Hayhoe et al. 2010).
<br />1,2 Oi%'er'vIli" r "NPi(Cof of at
<br />Change on S,,,:"ll��Y�clli`es and 14abIliilati°ir
<br />Ecosystem processes are strongly influenced by
<br />climate, and changes in climate will affect ecosys-
<br />tem processes, ecological communities, and indi-
<br />vidual species. Climate change has been implicated
<br />in several recent species extinctions (McLaughlin et
<br />al. 2002, Pounds et al. 2006). Largely in response
<br />to environmental factors associate with changes
<br />in temperature, species ranges have shifted pole -
<br />ward and upward in elevation over the last century
<br />(Parmesan and Yohe 2003), and some species ranges,
<br />particularly in Polar Regions and at high elevations,
<br />are shrinking. Furthermore, changes in the timing
<br />of biological processes (phenology) are occurring,
<br />altering relationships between species and decou-
<br />pling critical species interactions (Walther et al.
<br />2002). Ecological communities are disaggregating,
<br />and as new and often novel communities assemble,
<br />warm - adapted and invasive species may be favored
<br />(Parmesan 2006, Hellmann et al. 2008). Species are
<br />also losing habitat due to sea level rise, changes in
<br />fire frequency and intensity, changes in water avail-
<br />ability, glacial recession, pest outbreaks and altered
<br />weather patterns. Species invasions, as well as pest
<br />and disease outbreaks, are becoming more prevalent
<br />under climate change and, taken with other ongo-
<br />ing threats, are likely to significantly impact native
<br />species and ecosystems.
<br />l i r1 a t l'" /1 a l lI e l i r l /,',I at" t_!; w l l' I
<br />x.111' "r'll l'll,br I /t' Y "111'11/ t11!;/ ('" 1 i
<br />Climate exerts control over the natural distribution
<br />of species and the formation of ecological commu-
<br />nities. The diversity of species within ecological
<br />communities is influenced by a combination of local
<br />and regional -scale processes (Caley and Schluter
<br />1997). Local -scale interspecific interactions include
<br />competition, predation, parasitism, mutualisms
<br />or commensalisms, while regional -scale processes
<br />shape the species pool from which the community
<br />can be assembled. Regional processes that main-
<br />tain diversity at a larger scale include long - distance
<br />dispersal, speciation, wide- spread extinction, and
<br />fluctuation in species distributions (Cornell and
<br />Lawton 1992). Ecological communities have always
<br />been dynamic— species diversity and composition
<br />within a community is temporary and, as species
<br />respond individualistically to changes in environ-
<br />mental conditions, communities may diasassociate,
<br />resulting in new species associations and interactions
<br />(Huntley 1991).
<br />Climate change will alter the abiotic conditions
<br />experienced by communities, with resulting effects
<br />on community composition and species interactions.
<br />As climate changes across the globe, the current
<br />distribution of climate conditions will be rearranged,
<br />with some climates disappearing entirely and new,
<br />dissimilar climates occurring. Using two emissions
<br />scenarios, Williams et al. (2007) estimated that by
<br />2100, 17 -100% of global land area will experience
<br />novel climate regimes. For the U.S., approximately
<br />half of environmental domains, defined by edaphic,
<br />topographic and climatic factors, were projected to
<br />experience novel climates. Areas projected to experi-
<br />ence novel climate conditions are considered to be at
<br />greatest risk of biodiversity loss (Saxon et al. 2005).
<br />Paleoecological studies suggest that the majority of
<br />species will respond individualistically to changes in
<br />climate (Huntley 1991, Hansen et al. 2001, Bush
<br />2002). The fossil record from the Quaternary Period
<br />
|