Trees are growing faster and could buy time to halt global warming

Trees are growing faster and could buy time to halt global warming. By Urmee Khan
The Telegraph, Apr 06. 2009, 9:01AM BST

The phenomenon has been discovered in a variety of flora, ranging from tropical rainforests to British sugar beet crops.

It means they are soaking up at least some of the billions of tons of CO2 released into the atmosphere by humans that would otherwise be accelerating the rate of climate change.Plants survive by extracting CO2 from the air and using sunlight to convert it into proteins and sugars.
Since 1750 the concentration in the air has risen from of CO2 278 parts per million (ppm) to more than 380 ppm, making it easier for plants to acquire the CO2 needed for rapid growth.

A study by the University of Leeds, published in the science journal Nature, measured the girth of 70,000 trees across 10 African countries and compared them with similar records made four decades ago.

On average, the trees were getting bigger faster and researchers found that each hectare of African forest was trapping an extra 0.6 tons of CO2 a year compared with the 1960s.
If this is replicated across the world's tropical rainforests they would be removing nearly 5 billion tons of CO2 a year from the atmosphere.

Scientists have been looking for a similar impact on crop yields and the experiments generally suggest that raised CO2 levels would boost the yields of mainstream crops, such as maize, rice and soy, by about 13 per cent.

Professor Martin Parry, head of plant science at Rothamsted Research, Britain's leading crop institute, said: "There is no doubt that the enrichment of the air with CO2 is increasing plant growth rates in many areas.

"The problem is that humans are releasing so much that plants can remove only a fraction of it," he said.

Humans are believed to generate about 50 billion tons of the gas each year.

However, scientists have warned against drawing false comfort from such findings. They point out that although levels will boost plant growth, other factors associated with climate change, such as rising temperatures and drought, are likely to have a negative effect.

Fred Pearce, environment consultant for New Scientist, said: "We know that trees do absorb carbon dioxide from the atmosphere and about half is taken up from nature and half of that is by forests. But it doesn't change the story greenhouse gases are accumulating more than 2 per cent a year.

"It won't buy us much time as humans are releasing much more CO2 into the air, but it is useful information if it helps to protect existing forests."