Future generations to pay for our mistakes: biodiversity loss doesn't appear for decades

Jeremy Hance
April 15, 2013

The biodiversity of Europe today is largely linked to environmental conditions decades ago, according to a new large-scale study in the Proceedings of the National Academy of Sciences (PNAS). Looking at various social and economic conditions from the last hundred years, scientists found that today's European species were closely aligned to environmental impacts on the continent from 1900 and 1950 instead of more recent times. The findings imply that scientists may be underestimating the total decline in global biodiversity, while future generations will inherit a natural world of our making.

"The progressive impact of environmental degradation on the loss of global biodiversity is strongly linked to key socioeconomic indicators such as human population size, land use, and gross domestic product (GDP). However, species populations do not necessarily respond immediately to environmental degradation but might do so with a delay," the scientists write. This theory is known as 'extinction debt,' whereby it takes species several of their generations to show the full impact of habitat loss and other threats.

To test this theory, thirteen researchers looked at a broad array of threatened species (mammals, reptiles, fish, plants, dragonflies, and grasshoppers) across 22 European countries. Currently around 20-40 percent of these species are listed as threatened by the IUCN Red List. But the researchers found that some of the species groups—i.e. plants, dragonflies, and grasshoppers—were most closely aligned to European conditions of over a century ago: circa 1900. For mammals and reptiles, both 1900 and 1950 were most reflective, while fish was actually best correlated with contemporary conditions.

Therefore, the study finds evidence of an extinction debt of several decades for mammals and reptiles, and over a hundred years for plants and insects. As to why fish are different, the researchers weren't sure.

"We do not know why fish behave differently, but it might be that anthropogenic impacts on freshwater ecosystems, such as water pollution, channelization, construction of dams, and water abstraction, have a more immediate effect because they not only reduce the quality and quantity of habitats, but directly and uniformly modify the medium in which species live," the scientists write.

The researchers also note that species are now facing new threats that were largely absent in the early 20th Century, including a rapidly warming Earth and increased invasive species.

"Our results...suggest current commitments to stop biodiversity loss in the region are even more inadequate than currently appreciated," the researchers warn noting also that the global IUCN Red List "might be too optimistic." Given this, the scientists say conservation efforts will have to stepped up considerably to stave off mass extinction.

For decades, scientists have been warning that the Earth is nearing or already in the midst of a global mass extinction. Currently 21 percent of the world's mammals are listed as threatened by the IUCN Red List, 13 percent of the world's birds, 22 percent of the world's reptiles, and 30 percent of the world's amphibians.

Creek in Triglav National Park, Slovenia. Photo by: Rhett A. Butler.
Creek in Triglav National Park, Slovenia. Photo by: Rhett A. Butler.

CITATION: Stefan Dullinger et al. Europe's other debt crisis caused by the long legacy of future extinctions. PNAS. 2013.

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Jeremy Hance
mongabay.com (April 15, 2013).

Future generations to pay for our mistakes: biodiversity loss doesn't appear for decades.