Carbon sequestration is generally thought of as locking carbon out of the atmosphere semi-permanently by incorporating it into rocks or forests that are then preserved. But there's a large cache of carbon in a form that's not especially permanent: the wood we use in our buildings and other structures. Some of that lumber has been in place for hundreds of years, while other bits of wood are used temporarily and then burnt or left to decay, which rapidly releases their sequestered carbon back into the atmosphere.
So it shouldn't surprise you that figuring out how much carbon ends up sequestered through our use of wood products is not a simple task. Undaunted, Craig Johnston and Volker Radeloff of the University of Wisconsin, Madison, have decided to tackle it. By viewing that carbon as a pool that's being drained and filled at the same time, they find that the total sequestered carbon is tiny—and subject to rapid changes based on political and economic factors.
Into the woods
The secret to tracking this pile of carbon is to recognize that we're never going to have a full inventory of lumber that was put in place a century or more ago. But that lumber is going to be an ever-shrinking portion of the material that was put in place more recently. Thus, if we can track the production of lumber (and other wood products) over the decades for which we have good data (1960 and beyond), then we have a decent sense of the total inputs to this sequestered carbon.