Earth's extinction rate highly exaggerated: Study

Contrary to the current belief that about half of earth's plants and animals would go extinct over the next century because of human activities, a study has found that this extinction rate is overly exaggerated.

The reason for the discrepancies is that "island biogeographic theory" was originally based on actual islands surrounded by water, and does not account for factors such as a countryside landscape's ability to support more species and slow extinction rates compared to true island ecosystems, the researchers said.

Especially in the tropics, island biogeographic theory's application is "distorting our understanding and conservation strategies in agriculture, the enterprise on which the future of biodiversity most critically hinges".

"Not only do more species persist across the 'sea of farmland' than expected by 'island biogeographic theory', novel yet native species actually thrive there," said Elizabeth Hadly, senior fellow at the Stanford Woods Institute for the Environment.

"This indicates that human-altered landscapes can foster more biological diversity than we anticipated," Hadly said.

The researchers now point to an alternative framework that promises a more effective way of accounting for human-altered landscapes and assessing ecological risks.

"This paper shows that farmland and forest remnants can be more valuable for biodiversity than previously assumed," said Daniel Karp, post-doctoral fellow at University of California, Berkeley.

"If we are valuing coffee fields and other human-made habitats at zero, we're doing a disservice to ourselves and wildlife," said Chase Mendenhall, a doctoral student at Stanford University.

To test the island theory against a more holistic theory of agricultural or countryside bio-geography, the researchers turned to bats in Costa Rica and on islands in a large lake in Panama.

Bats are acutely sensitive to deforestation.

The researchers also did a meta-analysis of 29 studies of more than 700 bat species to bolster and generalise their findings globally.

The study appeared in the journal Nature.