A quick vacation to Washington’s Olympic Peninsula reminded me of two things. First — dang, those trees are huge!

Olympic rainforest

And second — dang, there’s a lot of clearcut coastal forestland that’s still just basically sitting there: no trees, just scrub and piles of decaying stumps.

Which got me to thinking: How much CO2 could the clearcut land store if returned to its full rainforest glory? Enough to take a serious bite out of our climate-warming emissions?

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Well, according to this study, a single acre of undisturbed, old-growth forest in coastal Washington stores more than 300 tons of carbon, counting soils, trees, foliage, and woody debris on the forest floor.

And according to this (PDF), carbon stores are reduced by more than half after a clearcut, due both to the loss of the trees themselves and the oxidation of carbon-rich forest soils.

Some interesting stuff follows.

Ultimately, restoring an acre of Washington’s coastal forest would sequester about 550 tons of CO2 that otherwise would be polluting the climate. That won’t happen overnight; it might take a few hundred years for the forest to regrow to match its pre-clearcut carbon storage. But on an annual basis, we can expect an acre of regrowing coastal forest to capture and store about two to three tons of CO2 per year.

How much is that? Counting gasoline, diesel, coal, natural gas, jet fuel, and minor petroleum products, the average Northwesterner puts about 12 tons of CO2 into the atmosphere each year. (Those are round numbers — and as this post points out, the Northwest’s emissions are lower than the U.S. average because so much of our electricity comes from hydropower.)

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So just to capture my personal share of CO2 emissions from fossil fuels, I’d have set aside and restore at least 4 acres of clearcut coastal rainforest.

This analysis of clearcuts on the Olympic peninsula showed that about a million acres of forestland were cut between 1971 and 2002. All of which means that the carbon captured by the regrowing forests is offsetting the fossil fuel emissions from at most 250,000 of the state’s 6.4 million residents. At most.

Anything helps — a 4 percent offset from fossil fuel emissions is better than no offset. But given that the Northwest’s coastal forests sequester carbon better than just about any ecosystem on the planet, it’s not nearly as much as I had hoped or expected.