Measuring the amphibian meltdown

9 01 2009

melting_frog_by_zarinstar.pngA paper my colleagues and I published earlier last year in the open-access journal PLoS One describes one of the largest databases of amphibian threat risk ever compiled. Our main aims were to determine which factors drive amphibians toward extinction – this being especially topical considering that amphibians epitomise the modern biodiversity crisis: major population declines, disease outbreaks, deformities and recent confirmed extinctions dominate the biodiversity news. 32 % of all amphibians worldwide are threatened with extinction, 43 % of described species are declining, and about 160 species have already gone extinct in the last few decades.

In our paper (Sodhi and colleagues) entitled Measuring the meltdown: drivers of global amphibian extinction and decline, we found that the range size occupied by a species was overwhelmingly the principal driver of threat risk. This means that although other factors are involved, the number one (by far and away) thing threatening amphibians is habitat loss – everything else is minor by comparison.

Of course, we shouldn’t ignore other issues – increasing climate seasonality (temperature and precipitation) also contributed to higher threat risk. This is exactly the sort of thing that is predicted to increase with climate change (more variable weather patterns). In many cases, it’s the variability that’s worse than the mean trend when it comes to biodiversity.

So what should we do? Our results suggest that areas containing high numbers of restricted-range amphibians should have conservation priority. Although captive breeding might help to buffer some declining populations in the short term, such interventions cannot substitute for habitat protection and restoration. The synergies between ecological/life history traits and environmental conditions demonstrate how management must address each of the major drivers of decline together for any success – there is no magic bullet to prevent extinctions. We also recommend that substantial increases in international research on the long-term monitoring of amphibian populations is required to mitigate effectively the current meltdown of amphibian biodiversity.

CJA Bradshaw

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