WASHINGTON, June 6 (Xinhua) -- Forests in many regions are becoming larger carbon sinks thanks to higher density, U.S. and European researchers say in a new report.

In Europe and North America, increased density significantly raised carbon storage despite little or no expansion of forest area, according to the study, led by Aapo Rautiainen of the University of Helsinki, Finland, and published Monday in the on- line, open-access journal PLoS One.

Even in the South American nations studied, more density helped maintain regional carbon levels in the face of deforestation.

The researchers analyzed information from 68 nations, which together account for 72 percent of the world's forested land and 68 percent of reported carbon mass. They conclude that managing forests for timber growth and density offers a way to increase stored carbon, even with little or no expansion of forest area.

"In 2004 emissions and removals of carbon dioxide from land use, land-use change and forestry comprised about one fifth of total emissions. Tempering the fifth by slowing or reversing the loss of carbon in forests would be a worthwhile mitigation. The great role of density means that not only conservation of forest area but also managing denser, healthier forests can mitigate carbon emission," says Rautiainen.