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FEARS that soil boosts global warming by releasing massive amounts of
greenhouse gases into the air may be unfounded.

A Scottish soils scientist who has in the past warned of the threat now says
that soil could be better at soaking up carbon dioxide from the air than we
think. 鈥淢odellers may have to think again about whether the large carbon
reservoir in soils is actually as vulnerable as has been supposed up to now,鈥�
says Melvin Cannell, director of the Centre for Ecology and Hydrology in
Penicuik, near Edinburgh.

One of the big fears climate scientists have is that, as the world warms,
microbes in soils will break down organic matter such as dead plant roots faster
than before. This would produce a rush of carbon dioxide into the air, which
would speed up global warming.

鈥淢odellers have assumed that this process goes up more or less exponentially
with rising temperature,鈥� says Cannell. 鈥淏ut recent studies suggest that warming
may not be depleting soil carbon as much as predicted.鈥�

This could be because microbes don鈥檛 respond to warmer temperatures as much
as first thought. But Cannell has discovered another possibility鈥攖hat the
carbon is going somewhere other than the atmosphere.

He and colleague John Thornley say their models reveal that warming could
speed up a variety of chemical processes in soil that would effectively bury the
carbon lower down, where microbes cannot get at it. Warming may affect soil
chemistry far more quickly than microbes, locking carbon away permanently, the
researchers add.

This theory is good news for governments who want to fight global warming by
finding ways of making soil absorb more carbon. There have been fears that such
soil 鈥渟inks鈥� could be undone by global warming itself. But the new findings
鈥渟uggest that carbon stored in soils is more secure than previously thought鈥�,
says Cannell.