Lush and lofty, the big trees in a 520-acre forest gracing the vista of Mount Rainier are now doing double duty, in the first-ever carbon-capture program of its kind in the Pacific Northwest.

Microsoft bought the carbon credits in this forest under California's rigorously verified cap-and-trade program. Washington state has no such program. The purchase was part of the company's voluntary $20 million-a-year effort offsetting 100 percent of its carbon emissions worldwide across all operations, from employee air travel to energy use.

The forest, near Ashford in the Nisqually watershed, will generate 37,000 carbon-offset credits, the equivalent of taking 6,000 cars off the road. And the total will get bigger as the trees do.

Microsoft bought 35,000 of the credits from the Nisqually Land Trust for an undisclosed price. The purchase helped the trust buy the $3.3 million property, taking the land out of industrial forestry, with its shorter rotations before harvest. Under the program and the land trust's ownership, the trees will have a chance to get big and fat, as they gobble from the air for at least the next 100 years.

Through photosynthesis, trees, using only water and light energy from the sun, split the carbon from carbon dioxide to make sugar for food. Trees are the carbon cycle made visible: They take the carbon molecules that are warming our atmosphere right out of the air and store them in their wood, roots and leaves. The bigger the tree, the more carbon it stores.

Enlisting forests in the fight against global warming does double duty, notes Becky Kelley, president of the Washington Environmental Council, which helped put the deal together. Carbon-credit programs provide landowners the financial incentive to keep rather than cut them. And they provide a reason for credit purchasers to invest in preserving forests.

Every tree counts, but bigger trees at least 40 years old are the real carbon hogs that get the work of cleaning the air done. With their larger root mass, they also are the champions of holding soil and cleansing water.

Trees don't just stand there, they make life, and sustain it. The Nisqually forest benefits threatened spotted owls and marbled murrelets, as well as a catenation of other animals, from bats to swifts, frogs, cutthroat trout, pileated woodpeckers and Northern goshawks.

"Forests provide so many values beyond lumber," Kelley said. "Yet those other benefits aren't well accounted for financially; it can be hard for landowners to make it pencil. We are trying to get people to grow bigger trees and leave them standing longer.

"Older forests are a twofer in terms of helping us deal with ," Kelley said. "They pull pollution out of the air and help moderate the effects of climate change on our communities."

Joe Kane, executive director of the Nisqually Land Trust, notes the purchase also creates the revenue the trust needs to maintain the forest over the years, for taking out logging roads, or thinning to help the forest achieve robust growth.

For Microsoft, the forest was a way to look closer to home for its ambitious carbon-offset program, which includes projects all over the world, said Rob Bernard, chief of environmental strategies for Microsoft.

"We have been looking for an opportunity in our home state, and this was an easy one to get excited about," Bernard said. The company voluntarily deploys a range of strategies to be carbon neutral.

Every Microsoft department is charged an internal fee based on the amount of produced. Money from the fee is used to pay for energy-efficiency projects and the purchase of green power, and to deploy 30 projects in 23 countries to offset the company's carbon pollution, with everything from cleaner cook stoves in Kenya, to solar water heaters in India, and forest preservation and replanting in Borneo.

The fund also pays for grants for employees with project ideas of their own, such as an electric-bike program running in Finland.

In addition to offsets, the company seeks to reduce its emissions through energy-efficiency initiatives and purchases of green power, Bernard said. Microsoft is the second-largest purchaser of in the United States, according to the U.S. Environmental Protection Agency.

Since its inception, the overall program has reduced Microsoft's carbon-dioxide emissions by 7.5 million metric tons, the equivalent of nearly 18 billion miles driven by cars, according to calculations by the EPA.

The carbon-neutral policy enables Microsoft's customers to offset some of their own pollution, by using the company's cloud computing services, Bernard said. "As we move to cloud computation and have more responsibility for not only creating the software but running and managing it, this is a new benefit for our customers."

The company began the offset program three years ago, Bernard said. "We just believe it is important to be accountable for our carbon. It's important to do this for ourselves, and our customers, and the planet."

Programs like Microsoft's Nisqually purchase could become more common under a carbon cap being drafted by the state Department of Ecology, at the request of Gov. Jay Inslee. His more ambitious cap-and-trade program, similar to California's, cratered in the Legislature last year. The cap now in the works can be implemented without legislative approval.

Under it, the state's largest emitters would have a choice of reducing carbon pollution on site, or buying credits through the California program or others that result in verifiable net reductions of , to keep big polluters under the mandatory cap.

Two ballot initiatives also are brewing to implement more aggressive action against pollution.

The state implemented greenhouse-gas reduction goals in 2008 but so far it is not on track to meet them. It will take more reductions and changes in business as usual for Washington to do its part in the global problem of climate warming, said Stu Clark, air quality manager for the department.

The department is striving to implement the rule by next summer. But even that won't be enough to meet the state's targets, because the cap doesn't have the scope or sweep of what the governor originally sought. The cap will capture only about 60 percent of total emissions.

"Climate change is the defining environmental issue of our time," Clark said. "Everybody needs to step up."