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Climate change threatens a million species with extinction

January 07, 2004

Climate change may drive a quarter of land animals and plants extinct, according to a major new study published in the journal Nature - unless greenhouse gas emissions are drastically reduced.

The largest collaboration of scientists ever to apply themselves to this problem studied six biodiversity-rich regions around the world representing 20% of the planet's land area. They projected the future distributions of 1103 plants, mammals, birds, reptiles, frogs, butterflies and other invertebrates. The study employed computer models to simulate the ways species' ranges are expected to move in response to changing temperatures and climatic conditions. Three different climate change scenarios were considered - minimum, mid-range and maximum expected climate change using data supplied by the Intergovernmental Panel on Climate Change. The ability of animals and plants to move to new areas was also considered, using two alternatives; one where species could not spread at all, the other assuming "unlimited" or successful movement.

The study found that 15 to 37% of all species in the regions considered could be driven extinct from the climate change that is likely to occur between now and 2050 (i.e., for mid-range climate warming scenarios). The scientists believe that extinctions due to climate change are also likely to occur elsewhere. "If the projections can be extrapolated globally, and to other groups of land animals and plants, our analyses suggest that well over a million species could be threatened with extinction as a result of climate change," said lead author Chris Thomas of the University of Leeds, England.

"This study makes clear that climate change is the biggest new extinction threat," said co-author Lee Hannah, at Conservation International (CI) in Washington DC. "The combination of increasing habitat loss and climate change together is particularly worrying. Increases in temperature can force a species to move toward its preferred, usually cooler, climate range. If habitat destruction has already altered those habitats, the species will have no safe haven."

"In some cases we found that there will no longer be anywhere climatically suitable for these species to live; in other cases they may be unable to reach distant regions where the climate will be suitable. Other species are expected to survive in much reduced areas, where they may then be at risk from other threats," said co-author Guy Midgley of the National Botanical Institute in Cape Town, South Africa.

"Seeing the range of responses across all 1103 species, it becomes obvious is that we have a lot of work left to do before we can accurately predict what types of animals and plants are most at risk. This range of responses shows that species will not be able to move as whole biological communities, and that the typical natural communities we recognise today will probably not exist under future conditions. Figuring out what will replace them requires a lot of imagination," said co-author Alison Cameron, also from the University of Leeds.

These forecasts are for species predicted to go extinct eventually based on the climate change that will occur between now and 2050. However, as some species respond slowly to environmental change, many of the species that may be doomed to eventual extinction will not actually have become extinct by 2050.

What can be done?

The Nature paper concluded that "Minimum expected (i.e., inevitable) climate change scenarios for 2050 produce fewer projected extinctions (18% averaging across the different methods) than mid-range projections (24%), and about half those predicted under maximum expected climate change (35%)." Thus, 15-20% of all land species could potentially be saved from extinction if minimum, rather than maximum, climate warming is achieved.

The recent rise in global temperature is attributable to human induced activities that have altered the chemical composition of the atmosphere. The buildup of greenhouse gases - primarily carbon dioxide, methane, and nitrous oxide - traps heat, acting much like a greenhouse in the atmosphere.

"A key aspect of this work is that it shows that even species existing in protected areas can be under imminent threat from climate change. Maintaining natural habitats is essential, but not always sufficient, to permit species to survive. The problem of climate related extinction is only realistically tackled through governmental and international energy and emissions policies," said Cameron.

"An immediate and progressive switch to technologies that produce little or no new greenhouse gases, combined with active removal of carbon dioxide from the atmosphere, could save a million or more species from extinction," said Thomas.

Leeds, University of