“Watching how the species of amphibians change actually tells you more about how the species of birds are turning over than watching for changes in the environment,” Lauren Buckley of the National Center for Ecological Analysis and Sythesis, US, told environmentalresearchweb. “This confirms the role of amphibians as ‘canaries in the coal mine’. Amphibians are likely to be the first to respond to environmental changes and their responses can forecast how other species will respond.”

Together with Walter Jetz of the University of California at San Diego, Buckley found that in mountainous regions such as the Andes and Himalayas, the identities of amphibians and birds changed particularly quickly with location. And species changed faster in the tropics than in temperate regions.

“This supports an old idea that ‘mountain passes are higher in the tropics’ – that species are more specially adapted to particular environmental conditions in the tropics leading to faster spatial turnover,” said Buckley. “As a result, tropical species may be more severely impacted by a given temperature increase as a result of climate change.”

There appears to be a link between the rate of turnover and the species’ geographic range. While the rate of amphibian turnover was four times steeper than for birds, the average geographic ranges of birds are four times larger than those of amphibians. What’s more, narrow-ranged birds showed rapid changes in species with space, similar to those for amphibians.

Although there are many maps that depict how many species occupy each location on earth, there are very few that show how species in one location differ from those in a neighbouring one, say the researchers. “However, considering both of these aspects of biodiversity is central to conservation planning,” they add.

Buckley believes that understanding the influence of environmental changes over space on biodiversity patterns can provide important background for forecasting how biodiversity will respond to environmental changes over time, such as temperature increases.

“Any hiker realizes that the types of animals you see change more rapidly as you hike in a mountainous region than in the plains,” she said. “Yet few studies have directly linked changes in environmental conditions to changes in species composition. Understanding how changes in the environment influence biodiversity is particularly important in the face of accelerating climate change.”

The researchers reported their work in PNAS.