Scientists have described as a "disaster" a research finding that shows soils across Britain are discharging carbon dioxide into the environment due to global warming.
Moreover, this release, in turn, could speed up climate change as warmer weather accelerates the rate that carbon in the soil moves away into the atmosphere.
The surprise finding by researchers at Cranfield University also reduces the hoped for benefits expected to come from the carbon control measures introduced by the Kyoto greenhouse gas agreement.
Even as efforts are made to bring carbon emissions under control soils across Britain are annually releasing an estimated 13 million tonnes of carbon a year. Britain's Kyoto carbon target from all industrial sources is 150 million tonnes a year.
A similar release from temperate zones could be happening right around the world according to Prof Guy Kirk and Prof Ian Bradley who publish their findings this morning in the journal Nature. "If our findings are correct we expect it will be happening in other temperate areas," Prof Kirk said yesterday at a session of the BA Festival of Science, underway this week at Trinity College Dublin.
Their results are based on a National Soil Inventory carried out between 1978 and 2003. An initial 5,600 sites across Britain were measured for carbon content and then a follow up was done to see how levels had changed over the intervening years, given a 0.5 degree increase in average annual temperatures. They found that soils of all types were losing on average about 0.6 per cent of their carbon a year, arising mainly as carbon dioxide gas. This represents about 15 per cent of soil carbon since the study began, Prof Kirk said yesterday.
Soil gains carbon when dead plants and other organic material work their way into the ground. It loses carbon when microbes digest this material, in the process emitting carbon dioxide, Prof Kirk explained.
Plants grow better when carbon dioxide is plentiful, so researchers have long maintained that more rapid plant growth would soak up perhaps 25 per cent of the extra carbon dioxide in the atmosphere.
Climate change helps microbes however who produce carbon dioxide faster as the weather warms. Researchers have also found that the hoped for 25 per cent "buffer" is less than expected. This process looks set to accelerate with more carbon dioxide producing higher temperatures which in turn encourages microbes to produce more gas.
The finding is a "disaster" Prof Kirk said. "The consequence is there is more urgency about doing something.
"The consequences of global warming will arrive faster. This is the scary thing about it, the amount of time we have to do something." The losses in Britain appear to be happening regardless of how the land is used, which adds weight to the idea that climate change is to blame, the researchers said. Soils with the most carbon seem to be losing carbon faster however. "The more organic the soil the greater the loss," Prof Bradley said.
