Mediterranean Ecosystems Worldwide: Climate Adaptation - Recent Advances and Issues in Environmental Science - page 31

The mediterranean biome's extraordinary plant diversity and endemism are a result
of the evolutionary processes induced by the characteristically unique annual cycles
of extended summer drought and cool wet winter, high topographic variation, and low
soil fertility [9]. Climate change resulting from increases in atmospheric concentra-
tions of greenhouse gases will impact the extent and distribution of the mediterranean
climate, posing a threat to the survival of many species. While biome level analyses
are rare, there has been a recent proliferation of climate change impacts studies spe-
cifi c to species and habitats in each of the fi ve mediterranean regions [10-14]. These
studies generally project signifi cant reductions in endemic species range sizes. For
example, in California, 66% of the endemic plant taxa will experience >80% range
reductions within a century [14]. Midgley et al. projected a 51-65% reduction in the
mediterranean biome in South Africa by 2050, and that only 5% of the endemic Prote-
aceae species modeled would retain more than two-thirds of their current range [15].
However, each of these studies is limited to one of the fi ve mediterranean regions
and generally focuses on the results from one to a few of the 23 AOGCMs. In this
analysis, we focus on projected shifts in the mediterranean climate using a consistent
methodology worldwide. This allows for comparisons between regions and highlights
areas that are in most urgent need for climate change adaptation action. We present the
fi rst biome-level analysis of global climate change using all AOGCMs analyzed in the
Intergovernmental Panel on Climate Change's (IPCC) Fourth Assessment Report [16].
Finally, we estimate the potential for facilitation of species adaptation within a region
via the climatic stability of protected areas or via the migration pathways to optimal
climatic conditions, based on current distribution of areas managed for biodiversity
conservation, current patterns of land conversion, and magnitude of future impacts
of climate change. We refer to this measure as extrinsic adaptation potential which il-
luminates characteristics of the landscape that facilitate species adaptation, in contrast
to species-specifi c characteristics that determine intrinsic adaptation potential such
as dispersal ability or genetic diversity. Intrinsic and extrinsic adaptation potential
together defi nes the adaptation potential of a species.
MATERIALS AND METHODS
The mediterranean biome is typically mapped using a combination of climate char-
acteristics and plant assemblages that vary by region. One widely-used delineation of
this biome is a collection of ecoregions mapped by the World Wildlife Fund that cov-
ers 2.2% of the earth and is based upon climate and plant associations [2]. As the cli-
mate changes, the impacts on the climate characteristics across all five mediterranean
regions will be mechanistically similar, but the impacts on the plant assemblages will
differ as the definition and composition of mediterranean vegetation differs among re-
gions. For this reason, this analysis focuses on the climatic impacts and maps the MCE
across all five regions based solely on climatic factors and not plant assemblages.
Although there are varying defi nitions for the mediterranean climate, we chose
one defi nition that can be readily mapped with available climate data and has minimal
over prediction into areas that are not part of the mediterranean biome. According to
this defi nition, published by Aschmann [17], an area is within the MCE if it meets fi ve