Environment Counts | Amphibian population declines likely to accelerate
Author: Geoff Zeiss – Published At: 2011-12-04 17:35 – (873 Reads)
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Amphibian population declines far exceed those of other vertebrate groups, with 30% of all species listed as threatened. The causes of these declines probably include climate change, land-use change and fungal disease. Amphibian declines are likely to accelerate in the twenty-first century, because multiple drivers of extinction will jeopardize their populations more than previous assessments have suggested.
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conducted the first first global assessment of amphibians to provide a context for the well-publicized phenomenon of amphibian declines. Amphibians are more threatened, and aredeclining more rapidly, than either birds or mammals. This article
reports on an assessment of the spatial distribution and interactions of the primary threats to amphibian species. It is shown that the greatest proportions of species negatively affected by climate change are in Africa, parts of northern South America and the Andes.
Threats to amphibian biodiversity
The primary threats to amphibian biodiversity are climate change, land-use change and fungal disease (chytridiomycosis). Regions with the highest projected impact of land-use and climate change coincide, but there is little spatial overlap with regions highly threatened by fungal disease.
Overall, the areas with the richest amphibian faunas are disproportionately more affected by one or multiple threat factors than areas with low richness. Amphibian declines are likely to accelerate in the twenty-first century, because multiple drivers of extinction could jeopardize their populations more than previous, mono-causal, assessments have suggested.
The authors analyze a nearly complete global data set of 5,527 amphibian species to project how the spatial interaction of three important threats, climate change, chytridiomycosis and land-use change, could affect global amphibian diversity between 1980 and 2080.
Climate change
Threat from future climate change was estimated as the proportion of species locally losing climatic suitability per area. Because the spatial distribution of species richness varies considerably among the three amphibian orders Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians), climate change analyses were performed separately for each group.
Chytridiomycosis
Threat from chytridiomycosis was quantified as the future probability of occurrence of the fungus from a bioclimatic model projection.
Bioclimate envelope models (BEMs) were fitted for 5,527 amphibian species from the three amphibian orders Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians).
Climatic data were obtained from the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project phase 3 (CMIP3) multi-model data set of the Fourth Intergovernmental Panel on Climate Change (IPCC) report.
Land-use change
Estimates of future land-use change from natural to human-encroached were based on the projections of the Millennium Ecosystem Assessment. The Millennium Ecosystem Assessment uses four scenarios representing a variety of socio-economic and political futures to estimate future changes in the Earth’s land-cover,
- Adapting Mosaic
- Global Orchestration
- Order from Strength
- TechnoGarden
The Millennium Ecosystem Assessment maps provide information on current and future distributions of 18 different land-cover types.
