Despite little or no expansion of forest area, the increased density significantly raised the forests' ability to take up and sequester carbon emissions, a release from Rockefeller University said Monday.
Even in South America, researchers said, increased density helped maintain regional carbon levels in the face of ongoing deforestation.
"The great role of density means that not only conservation of forest area but also managing denser, healthier forests can mitigate carbon emission," Aapo Rautiainen of the University of Helsinki, Finland said.
"Forests are like cities -- they can grow both by spreading and by becoming denser," says co-author Iddo Wernick of Rockefeller University's Program for the Human Environment.
As an example, researchers found that while U.S. timberland area grew only 1 percent between 1953 and 2007, the combined national volume of growing stock increased by an impressive 51 percent as national forest density increased substantially.
"We are pleased to report that, of 68 nations studied, forest area is expanding in 45 and density is also increasing in 45," University of Helsinki researcher Pekka Kauppi said. "Changing area and density combined had a positive impact on the carbon stock in 51 countries."