The
Global Amphibian Decline:
Trends, Causes, and Challenges
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The
Global Amphibian Decline: |
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Mexican treefrog (Smilisca
baudinii) |
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Global
Trends Causes
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Global Trends It is apparent that local populations of many amphibian species
have declined substantially in the last several decades, and evidence
from several well-documented cases suggest declines at and above the level
of regional metapopulations. Population declines have been found on every
continent that contains amphibians, most well-documented in North,
Central, and South
America, Europe, and Australia,
yet there are also many populations that have not demonstrated any decrease.
Also, some stable species are even found in the same regions or local
habitats of other species that are in decline. Regardless, quantitative
analysis of population data from hundreds of amphibian populations suggests
that a global decline is taking place, and has possibly been occurring
over the last several decades, with relatively more declines in North
America and Australia/New Zealand than
in other regions. These declines also have demonstrated wide geographical
and temporal variability. One problem confounding researchers' efforts to identify systematic population declines is the complexity of amphibian population dynamics. Because many amphibian species occur as metapopulations, the dynamics of local populations may be poor indicators of the status of a particular species. Moreover, because recruitment is highly variable, most local populations are likely to fluctuate substantially in size. The fluctuations of local populations are important to amphibian conservation biology, since the magnitude of population fluctuations can indicate the risk of local extinction from demographic or environmental stochasticity. Subpopulations also likely decrease more often than they increase, with rapid and high recruitment in an environmentally favorable breeding season followed by slower declines. |
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