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"Time Machines" Predict Future of Plants with Climate Change

Bert Drake with greenhouseI am in a wetlands south of Annapolis, striding down a blue plastic walkway over the marsh. 

On both sides of the raised platform is a meadow of sedges (Scirpus olneyi) and fine, soft grasses (Spartina patens). The grasses form a lush green carpet from the Rhode River, a Chesapeake Bay tributary, to a curtain of oak and sweetgum trees that mark the edge of a forest on higher and drier land in Edgewater, Maryland.

Out of the marshlands sprout what looks extra-terrestrial phone booths.  Forty-five octagons, made from metal and sheathed in clear plastic, flash in the July sun. From the machines curl wires and pipes.

These strange-looking vessels are like time machines.

Dr. Bert Drake, a plant physiologist with the Smithsonian Environmental Research Center, explains the octagons are small greenhouses, full of wetlands grasses and sedges. The pipes pump into the chambers varying concentrations of carbon dioxide (C02). Dr. Drake is trying to predict what future concentrations of carbon dioxide in the atmosphere will do to plant life on Earth. 

“The chambers allow us to measure the exchange of carbon dioxide in the atmosphere with the plants,” Dr. Drake said.

Some of the chambers receive 400 parts per million of C02, the level in the air today.  In other greenhouses, Drake pumps in 700 parts per million carbon dioxide. That is a level that many researchers predict will be in the Earth’s atmosphere later in this century, largely because of the burning of coal and other fossil fuels.

Do the higher pollution levels kill the plants?

Dr. Drake smiled. “In fact, they love it,” he said.  “Thinking of CO2 as a pollutant is an interesting question, of course, because it causes damage to our climate system.  We can look at it that way.  But it is absolutely essential for life.  We couldn’t exist without the plants taking carbon dioxide and making stuff that we can then eat and other animals can eat and allow us to exist on the earth.”

Over 19 years of study, Dr.Drake and colleagues concluded in a paper earlier this year that wetlands plants not only grow faster with higher carbon dioxide levels –they also consume more of the gas the faster they grow. 

For example, the sedges (Scirpus olneyi) are expected to gobble up 32 percent more carbon dioxide in the more polluted environment at the end of this century than they do today.  Even species of plants scientists did not expect to absorb more carbon dioxide –- such as the wetlands grass, Spartina patens -- experienced a 13 percent increase.

Dr. Drake said this suggests wetlands –- and by extrapolation, forests, and even grasslands  -- could become more of a buffer against climate change than scientists thought. The bad news is that this power of plants to consume more C02 is crippled by drought. And climate change is expected to cause more drought in certain regions. 

There is also a problem of scale.  The amount of C02 plants absorb is not nearly enough to keep up with the huge volume of the greenhouse gas people keep pumping into the atmosphere, Drake said.

“As the CO2 goes up, the plants will absorb a little more CO2. That story about the plants is embedded in the larger story of the effects of C02 on climate system,” Dr. Drake explained. “The predictions are that there will be droughts, and we are already seeing that in Australia, for example, and the southwestern part of the United States.  Droughts there lead to increase in fires.  We see effects on sea level – sea levels are coming up.  And we saw Superstorm Sandy and the effects of that on New York last year.  All of these effects are going to accelerate as  the carbon dioxide in the atmosphere increases.”

The bottom line: More carbon dioxide may be good for plants. But it won’t be for humans  -- especially our waterfront homes and cities.  So we should not expect the trees to rise up and save us from climate change, or the wetlands to wash away the consequences of burning fossil fuels.

By Tom Pelton

Chesapeake Bay Foundation 


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