Article: Warm soil climate worry

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http://news.bbc.co.uk/2/hi/science/nature/4224272.stm

 

 

Warmer soils add to climate worry

By Jonathan Amos

BBC News science reporter, Dublin

 

Yorkshire Dales (PA)

It made no difference what the land was used for

Higher UK temperatures are causing soils to " exhale " large quantities of

carbon dioxide, probably accelerating global warming, scientists report.

 

They base their assessment on a huge analysis of soil samples gathered

from across England and Wales over 25 years.

 

The team says its findings, if extended to the whole of the UK, suggest

some 13 million tonnes of carbon are being lost from British soils each

year.

 

The Cranfield University group reports its work in the journal Nature.

 

The scientists say computer models used to forecast future climate

trends will now have to be revised because the calculations on which

they are based will be wide of the mark.

 

" Our findings suggest the soil part of the equation is scarier than we

had thought, " Professor Guy Kirk, of Cranfield University, told

journalists at the British Association's Festival of Science in Dublin,

Ireland.

 

" The consequence is that there is more urgency about doing something

- global warming will accelerate. "

 

Indeed, as an illustration of how big a problem this is, it is likely

the carbon lost from British soils since 1990 will have completely wiped

out any reductions the country might have made through technological

gains over the same period.

 

In the microbes

 

The National Soil Inventory of England and Wales is a remarkable

project; there is nothing to match it for its scale anywhere else in the

world.

 

At its beginnings in 1978, almost 6,000 soil locations were sampled at

various depths down to 15cm. Over the intervening years something like

40% of these sites have been re-sampled and their chemistry analysed in

detail.

 

Professor Kirk and his colleagues have been able to show that the two

countries' soils have given up around 0.6% of their carbon content per

annum - or just over four million tonnes in the 25 years to 2003.

 

And although changing how land is used - turning it from crops to

woodland, for example - can change its chemistry radically, over England

and Wales as a whole this did not seem to be a significant factor in

controlling what was going on.

 

The researchers were left with only one explanation - climate change.

Over the 25 years, temperatures in the two nations have risen by about

0.5C.

 

This, they say, would have increased the rate at which microbes in the

soil could have broken down dead vegetation - wood, leaves and roots -

and released its carbon content.

 

'Considerable' implications

 

The scientists cannot say for sure where all the carbon has gone. Some

will have been leached to deeper layers and into waterways but most of

it is likely to have gone straight into the atmosphere as carbon dioxide

(CO2) - the chief gas thought responsible for driving higher global

temperatures.

 

" If the mechanisms we describe are correct, this will be happening in

other temperate countries, " said Professor Kirk.

 

" And this is going to be more important in temperate countries than in

the tropics because three-quarters of the world's carbon in soils is in

temperate areas. "

 

Nature magazine asked two scientists from Germany's Max Planck Institute

for Biogeochemistry to assess the Cranfield work.

 

Detlef Schulze and Annette Freibauer said: " The scientific and political

implications of the new findings are considerable.

 

" Further research into the carbon cycle and on reducing CO2 emissions

must take full account of areas where large pools of organic carbon are

stored - or are being released.

 

" If we intend to stabilise the climate, such areas require much more

serious consideration. "