Forest density can curb global warming

Scientists have found that rising forest density in many regions is helping to curb global warming by soaking up carbon dioxide (CO2), the main greenhouse gas.

"Higher density means world forests are capturing more carbon," Finnish and American scientists said in a report in the online journal PLoS One.

Trees absorb CO2 as they grow and release it when they burn or rot. Deforestation is behind 12 to 20 percent of all emissions by human activities in places from the Congo basin to Papua New Guinea.

The recent study found that despite little change in forest area, the amount of CO2 stored in forests increased in Europe and North America between 2000 and 2010.

In Africa and South America, the total amount of carbon stored in forests fell at a slower rate than the loss of area, and some countries were found to have big carbon losses, including Indonesia and Argentina.

According to lead author of the study, greater density in countries such as China was probably linked to past forest plantings.

"Forests that were established in China a few decades ago are now starting to reach their fast-growing phase. That is a reason for rising density now," said Aapo Rautiainen of the University of Helsinki.

Measuring the density of a forest is much more complex than measuring the extent of a forest by photographing it from a plane or by satellite.

"There does need to be a greater sampling to be able to come to a legitimate and credible number for the carbon," said Iddo Wernick, a co-author at New York’s Rockefeller University.