But science needs to sharpen its tools for counting the value of forests before Utah's - and the nation's - forest lands can be tallied up for the cap-and-trade carbon marketplace of the future, the report says.

Author Ann Ingerson, a Wilderness Society economist, pointed out that analyzing the carbon-holding power of forests continues to be part science, part guesswork for a variety of reasons.

"We need to have a little humility about the conclusions we draw," she said.

At the same time, she added, since it is clear that managing forests wisely will be important in addressing climate change as the United States and the world move forward with policies to slow global warming.

"There's a lot we don't know about forest carbon, but we can't wait to act until we know it all."

Utah already has faced firsthand the problem of counting forests' carbon value - how to save it and how to spend it.

Gov. Jon Huntsman Jr.'s Blue Ribbon Advisory Panel on Climate Change tried to put a number on it, then had to recalculate, said Glade Sowards, a staff aide to the task force. The task force finalized its recommendations last fall, but now a new review by Duke University is wrestling with the problem again.

"It's something we really need to get a handle on," Sowards said.

He pointed out, however, that forests are an important factor in the state's greenhouse gas balance sheet, which basically subtracts the carbon-reducing abilities of forests and soils from the amount of greenhouse gasses generated by Utahns and their industries.

Utah's gross emissions are about 68.8 million metric tons a year. And, with "carbon sinks" in forests and soils at 12.3 million metric tons, the state can say its net emissions are about 56.5 million metric tons.

Randy Parker, chief executive officer of the Utah Farm Bureau and a member of the task force, agreed that the value of forests and agricultural lands is difficult to quantify but necessary to understand better.

"That is an area where we can come together and make strides that we could all agree on," Parker said.

fahys@sltrib.com

* Forests bank lots of carbon, with those in the lower 48 states holding reserves equal to more than 20 years of U.S. greenhouse gas emissions.

* The amounts of carbon they store vary, based on their different makeup and different locations. Public forests - especially conserved lands, such as wilderness areas - tend to hold more carbon than private ones, which account for a larger share of the nation's forestland.

* The carbon in trees above ground represents only about half of the carbon a forest stores. For Utah, the Wilderness Society estimated the total forest carbon at 2,800 million metric tons, based on 21 million acres of forest land.