More CO2 Means Bigger Trees

Imagine that:

Forests by the Chesapeake Bay are growing two to four times faster than expected these days, researchers have found - a signal that rising carbon dioxide in our atmosphere might be triggering noticeable changes in ecosystems in the Mid-Atlantic.

And though scientists warn it's no panacea, the accelerated growth in stands of hardwoods monitored for the past 22 years is an indication that forests might dampen or delay the impact of climate change at least for a while, by soaking up some of the greenhouse gases that most scientists believe are warming the planet.

"We clearly see an increase in growth in these forests lately," said Geoffrey Parker, a senior scientist at the Smithsonian Environmental Research Center in Edgewater. The 58-year-old forest ecologist said he's been methodically measuring the girth of trees since he began working at the facility in 1987.

By measuring the circumference of a tree's trunk, scientists are able to estimate its "biomass," the combined weight of its wood and leaves. On average, they say, the woodlands they're tracking are bulking up by an extra 2 tons per acre annually. That's as if a new tree 2 feet in diameter sprang up every year.

Parker said he and his colleagues, Sean McMahon and Dawn Miller, aren't sure exactly what's driving the growth surge or when it began. But they note that carbon dioxide levels in the air at the Smithsonian's research center have increased 12 percent in the time since Parker began monitoring the trees. That's roughly the same increase tracked in the air above Mauna Loa Observatory in Hawaii - the site of the longest continuous measurement of carbon dioxide in the Earth's lower atmosphere.

The trio of scientists published their findings this week in the Proceedings of the National Academy of Sciences.

Other studies have shown that plants will grow faster when raised in air enriched with more carbon dioxide. Parker's Smithsonian colleague Bert Drake has demonstrated a similar effect with a long-term study of marsh grass growth at the Edgewater center.

The Earth is a remarkably self-balancing system. When more CO2 is available the plants respond by using that natural fuel to grow bigger and faster, in turn putting out more oxygen for the rest of us.