Boulder, Colo. -- The Earth has about 16.2 million square miles of forests but scientists say research is needed to understand the forests' impact on climate change.

"As politicians and the general public become more aware of climate change, there will be greater interest in legislative policies to mitigate global warming," said atmospheric scientist Gordon Bonan of the National Science Foundation's National Center for Atmospheric Research in Boulder, Colo. "Forests have been proposed as a possible solution, so it is imperative that we understand fully how forests influence climate."

The complex relationships within forests both add and subtract from the equations that dictate the warming of the planet, he said.

"In the Amazon, tropical rain forests remove carbon dioxide from the atmosphere," said Bonan. "This helps mitigate global warming by lowering greenhouse gas concentrations in the atmosphere. These forests also pump moisture into the atmosphere through evapotranspiration. This cools climate and also helps to mitigate global warming.

"We need better understanding of the many influences of forests on climate, both positive and negative feedbacks and how these will change as climate changes," he added.

Bonan's study appears in the June 13 issue of the journal Science.

Copyright 2008 by United Press International.