Rising temperatures reducing ability of plants to absorb carbon, study warns

http://www.usatoday.com/tech/science/discoveries/2005-09-07-british-soil_x.htm

This is more than just a fluke and has been happening for at least the last decade. Soil is losing carbon and plants that could absorb it to balance the cycle are dying from the drought caused by the carbon escaping from the soil. A true viscious cycle. So this isn't about your pretty like graphs about the Middle Ages which you seem to be stuck in, this is about a clear indication of something that is already affecting our ability to feed people. Take your head out of your butt for once.
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Study finds British soil losing carbon
By Michael Mcdonough, The Associated Press
LONDON — Rising temperatures resulting from climate change are likely causing soil in England and Wales to lose large amounts of carbon, possibly further contributing to the greenhouse gas effect, according to a new British study which suggests the same trend could be affecting other countries.
Soils store vast amounts of carbon — more than twice as much as in vegetation or the atmosphere. The amount of carbon in the soil is constant if the amount entering from dead vegetation — wood, leaves and roots — is equal to the amount being lost as soil microbes decompose the vegetation, releasing carbon dioxide.

But research published Wednesday in the scientific journal Nature found a disturbance in this natural balance. It estimated that British soil is losing 13 million tons of carbon a year — equivalent to 8.2% of Britain's carbon dioxide emissions in 2004.

Many scientists believe that greenhouse gases like carbon dioxide trap energy in the atmosphere, leading to an increase in global temperatures and changes in climate and weather patterns.

The study, funded by the British government, found that the carbon losses affected all types of soil.

"The fact that the losses appear to be happening ... irrespective of land use suggests a link to climate change," the report said, adding that over the 25-year survey period the mean temperature in England and Wales had risen by 0.5 C (0.9 F).

"Microbes in the soil are more active at warmer temperatures. As temperatures rise, the turnover of soil carbon goes up," said report co-author Guy Kirk from the National Soil Resources Institute at Cranfield University north of London. Four of the team members came from the NSRI, and the fifth was from Rothamsted Research, a British agricultural research center.

Their study suggested that while the increased global growth in vegetation is absorbing some of the carbon dioxide released by human activity, this is being offset by the loss of carbon from the soil.

"The input side is going up because of carbon dioxide emissions, but the output is going up because of temperature rises," Kirk told The Associated Press in a phone interview.

"The rate of loss is exceeding the rate of input. Past predictions had said this would happen in 10 to 50 years' time, but this study shows it is happening much faster. It is happening already in England and Wales," he said.

In a commentary published in Nature, E. Detlef Schulze and Annette Freibauer of the Max-Planck Institute for Biogeochemistry questioned whether global warming was the reason.

"According to our current understanding of the sensitivity of soil respiration to warming, increased temperature alone seems to be too weak a driver," they wrote, adding that changes in rainfall may have a stronger effect on carbon-rich soils.

The British government-funded study was based on research that began 25 years ago. Scientists drew 5,662 soil samples from 6,000 sites across England and Wales between 1978 and 1983. The sites corresponded to the intersection points of a grid of 5-kilometer by 5-kilometer (3-mile by 3-mile) covering both countries. Some 340 of the sites — including urban areas and waterways — were unsuitable for taking soil samples.

About 40% of the sites were sampled again in later years. The resampling occurred in three phases: in 1994-95 for arable and rotational grassland sites; in 1995-96 for managed permanent grassland sites; and in 2003 for nonagricultural sites, including bogs, scrub and woodland.

The researchers said this was "the only soil inventory on such a scale anywhere in the world to have been resampled." Statistical projections showed that only 40% of the original sites needed to be resampled to accurately measure changes, Kirk said.

The study found that the overall annual rate of change in the upper 15 centimeters (6 inches) of soil was -0.64% a year, compared with the original carbon content. For types of soil containing more carbon, this rate increased, reaching a rate of -7.37% a year for those sites richest in carbon.

The researchers estimated that the annual loss from soil across the United Kingdom — including Scotland and Northern Ireland — was 13 million tons of carbon per year. In 2004, carbon dioxide emissions in the United Kingdom reached 158.4 million tons, measured in carbon equivalent, according to Britain's Department for Environment, Food and Rural Affairs.

Britain has set a target of cutting carbon dioxide emissions by 20% below 1990 levels by 2010. But in 2003, carbon dioxide emissions rose 2.2%.