Climate has its say

Land formation does not get to decide biodiversity alone  

By Diya Das
Published: Wednesday 30 June 2010

imageTHE Himalaya bordering the north and the Western Ghats in the south of India form biodiversity hotspots. Given this evidence one can assume that areas with greater variety in landscape are home to a greater number of species.

General observation backs this theory: mountains have more biodiversity than plains just as tropics are richer in natural wealth than the poles. John A Finarelli and Catherine Badgley from the University of Michigan in the US say it is not the complete truth. They argue that climate and land formations both contribute to diversity. The present distribution of animals has changed several times since life began. There were times when plains harboured more life than hills.

When Earth’s tectonic plates push or pull against one another, they result in varied forms of land which translate into varied habitats and ergo, initiate formation of new species of animals and plants. The scientists studied fossil remains of prehistoric mouse-like rodents in the geologically active Rocky Mountains and the Great Plains in the US, dating from 25 to five million years ago—the Miocene epoch.

The Earth witnessed long-term cooling with intermittent warm periods in this era. The rodents’ diversity in the mountains reached its peak during a warm interval from 17 to 12 million years ago, also called the Miocene Climatic Optimum. This coincided with a period of intensive tectonic activity. During the cooling spells, the animals migrated to the plains.

“This study deals with the formation of large-scale continent patterns and shows these are not static through time and the pattern itself, not just the magnitude, is subject to change,” said John Finarelli, the lead author of the study published in the Proceedings of the Royal Society B on April 28.

“Similar patterns may exist in the Himalaya. Several elephant species and other mammals found there were pushed southward during periods of tectonic activity,” said T N C Vidya at Jawaharlal Nehru Centre for Advanced Scientific Research in Bengaluru. Since climate seems to play a role, humanmediated changes may be altering the planet’s diversity in ways unknown.

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