Comparative Losses of British Butterflies, Birds, and Plants and the Global Extinction Crisis

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There is growing concern about increased population, regional, and global extinctions of species. A key question is whether extinction rates for one group of organisms are representative of other taxa. We present a comparison at the national scale of population and regional extinctions of birds, butterflies, and vascular plants from Britain in recent decades.

We found that 28% of native plant species have decreased in Britain over the past 40 years, that 54% of native bird species have decreased over 20 years, and that a majority of butterfly species (71% over 20 years) has declined. Across the spectrum of changing distributions, butterflies have also fared worse than birds or plants: Two (3.4%) butterfly species became extinct in Britain between censuses compared with six (0.4%) native vascular plants over 70 years and no breeding bird species, and the most rapidly declining 10% of butterfly species experienced a 49% net loss in their occupancy of 10-km squares compared to birds (29%) and plants (22%). Similarly, the most rapidly increasing 10% of butterfly species showed net increases of only 21 to 164% in 10-km square occupancy compared to native birds (141 to 2900%) and plants (59 to 2583%). Population extinctions were recorded in all the main ecosystems of Britain, and were distributed with remarkable evenness across the nation, rather than concentrated in a few degraded regions

Despite the low diversity of Britain’s biota, we suspect that the relative changes reported here are not atypical. Certainly, the main drivers of change in British plant, bird, and butterfly populations are the same processes responsible for species’ declines worldwide. Our data sets may be unrepresentative of the wider world. Nevertheless, the important result here is that the only insect taxon to have been rigorously compared with plants or birds at this temporal or spatial scale experienced at least as many regional extinctions when exposed to the same range of environmental changes that afflict plants and vertebrates worldwide. If insects elsewhere in the world are similarly sensitive, the known global extinction rates of vertebrate and plant species have an unrecorded parallel among the invertebrates, strengthening the hypothesis that the natural world is experiencing the sixth major extinction event in its history.