Rising CO2 may benefit world's coastal wetlands

Washington, March 24 (ANI): In a paradoxical finding, scientists have discovered that an increase in carbon dioxide (CO2) may ironically counterbalance some of its negative effects on coastal wetlands, which are the planet's most valuable ecosystems.

The team conducted their study for two years (2006 - 2007), during which they focused on the role that organic matter, both growing and decaying, plays on soil elevation in wetlands and the effect CO2 has on this process.

Coastal wetlands must build upward through the accumulation of mineral and organic matter to maintain a constant elevation relative to water levels; otherwise, they will drown and disappear.

Climate change, however, is causing acceleration in the rise of sea level, which would seemingly put wetlands at risk of excessive flooding.

"Our findings show that elevated CO2 stimulates plant productivity, particularly below ground, thereby boosting marsh surface elevation," said Adam Langley, the research paper's lead author, who is the Smithsonian Environmental Research Center in Edgewater, Maryland.

According to Patrick Megonigal, the paper's corresponding author, "We found that by stimulating root growth, thus raising a marsh's soil elevation, elevated CO2 may also increase the capacity for coastal wetlands to tolerate relative rises in sea level."

These findings bear particular importance given the threat of accelerating sea-level rise to coastal wetlands worldwide.

To examine how CO2 may interact with other factors that will accompany sea-level rise, the authors also manipulated CO2, salinity and flooding in a companion greenhouse study.

The team of scientists from the Smithsonian Institution and the US Geological Survey added CO2 gas to a tidal marsh at the Smithsonian Environmental Research Center.

The gas flowed continuously from the bottom upward through the top of large (two-meter diameter) cylinders surrounding marsh plots.

Half of the plots also received added soil nitrogen, simulating increasing water pollution, which tended to diminish the positive effects of elevated CO2 on marsh surface elevation.

Changes in elevation were measured with an instrument developed by the US Geological Survey that can detect changes in elevation as little as one millimeter.

According to Langley, "Elevated CO2 doubled the short-term rate of elevation gain in our marsh. Our next step is to determine whether this will continue in the long-term and in the face of actual sea-level rise and other climatic changes." (ANI)