Although the plight of pandas has long been headline news, a new study indicates that conservationists should worry more about the extinction of butterflies and other insects. A comparison of changes in bird, butterfly, and plant populations across Great Britain suggests that, contrary to current thinking, unglamorous species may be disappearing even more rapidly than other organisms.
For decades, biologists have struggled to determine humans' impact on the flora and fauna around them. Insects and other invertebrates are so plentiful and cryptic that it's been hard to get a handle on their numbers or calculate the toll. Thus these researchers have used birds and mammals to monitor biodiversity, without many data to suggest this was the right approach.
Jeremy Thomas, an ecologist at the National Environmental Research Council Center for Ecology and Hydrology in Dorset, U.K., and his colleagues have now taken advantage of the work of thousands of volunteers who conducted several surveys over the past 50 years that included hundreds of species. The surveys covered 2861 10-kilometer by 10-kilometer areas across the United Kingdom and represent the most long-term work of their kind.
After a year of examining the data to make sure their analyses were sound, despite differences in when the surveys were done and the intervals between them, the researchers came up with clear results. Overall, between the first and second surveys, 28% of native plant species disappeared from at least one survey square. Half of the bird species showed a similar decline. Butterflies suffered the most, in total 71% of those species disappeared in at least one square, Thomas and his colleagues report in the 19 March issue of Science.
Additional data from more than a century's worth of records in a Dutch site tell a similar story. Thomas's team found that the extinction rate for butterflies was two orders of magnitude higher than that for plants and vertebrates. And other insects, including some wasps and flies, seem to be disappearing at alarming rates there as well.
These new results drive home a dire message. They “show that we have likely underestimated the magnitude of the pending extinctions,” says Stuart Pimm, an ecologist at Duke University in Durham, North Carolina.
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