Pumped Up on Carbon Dioxide, Vines Strengthen Their Grip

"We're getting more calls from the public," says Mark Smith of Maryland's Agriculture Department, near poison ivy. (By Susan Biddle -- The Washington Post)

"There's some reason for optimism that we could use vegetation to stave off global warming," said William H. Schlesinger, an expert on climate change and dean of the Nicholas School of the Environment and Earth Sciences at Duke University. "But there's no telling that the mix you come to is going to be stable or functional the way today's ecosystems are."

Trees and plants play a vital role in soaking up carbon dioxide that is released into the atmosphere. Scientists are trying to determine whether plants can keep pace with -- or perhaps even begin to reverse -- the rise in carbon dioxide.

For 20 years, Bert Drake has been exposing marsh grasses to twice as much carbon dioxide as normally found in the atmosphere. On a recent day, he strolled the wooden decking that winds through his laboratory, a swath of Chesapeake Bay marsh at the Smithsonian Environmental Research Center in Edgewater.

Drake said his research suggests that most plants grow faster on higher levels of carbon dioxide -- including plants already used as alternative fuels, such as switch grass. If burned instead of fossil fuels, these plants, the theory goes, could form a defense against climate change.

But whether every plant will grow faster in those conditions, or how fast, or at all, is maddeningly unpredictable.

At Edgewater, Drake found that most grasses grow about 35 percent faster in the altered atmosphere. But they are able to grow much faster than that, a variance he can't fully explain. Similarly, his experiments on oak trees in Florida found that each oak species responds differently to the same carbon dioxide overload.

"It's quite imaginable that we could make an oak tree [that is] more efficient at trapping carbon dioxide for us," Drake said. "But until we know a lot more about how each species responds, we can't make solid predictions."

In a Prince George's park, poison ivy, Japanese honeysuckle and other vines wind around most vertical surfaces and creep across the ground, looking for more.

"Anytime we move earth" -- for construction or repair projects -- "all we see is invasive species," said Mark Smith, who handles weed management at the Maryland Department of Agriculture. "We are seeing a tremendous variety of things, and we're getting more calls from the public."

In 1999, when the federal government recognized invasive plants as a national problem, Bergmann, of the Parks and Planning Commission, founded Weed Warriors, volunteers who patrol the region, ripping out offenders. Now an army of 500, they can't keep up. Many of the vines -- English ivy, porcelain berry, winter creeper -- were planted by homeowners who prized them as fast-growing, attractive ground cover.

"Just not buying these would really help a lot," she said. "I'd rather see native trees doing well than have some robotic tree developed that a vine can live on and create a super-jungle."