Salt Marshes Increase Carbon Capture In Warming Temperatures
September 27, 2012

As Temperatures Climb, Salt Marshes Curb Climate Change

Alan McStravick for — Your Universe Online

With only 6 days separating us from the third-hottest summer on record, the warnings of climate scientists are increasingly being taken with more than just a grain of salt. Many climate scientists are of the opinion that if we haven´t passed a tipping point already, then that time is rapidly approaching.

Carbon dioxide, one of the most prevalent of our greenhouse gases, acts as a sort of blanket in our atmosphere by trapping in the Earth´s heat. As carbon dioxide accumulates, it has the ability to affect our global climate, increasing temperature that, in turn, melts polar ice caps and causes sea levels to rise.

In a study published today in the journal Nature, environmental scientists from the University of Virginia postulate that the warming climate and rising seas will actually enable salt marshes around the globe to capture and remove increasing amounts of carbon dioxide from the atmosphere.  Potentially, this could act to slow the rate of global climate change.

"We predict that marshes will absorb some of that carbon dioxide, and if other coastal ecosystems — such as seagrasses and mangroves — respond similarly, there might be a little less warming," said the study's lead author, Matt Kirwan, a research assistant professor of environmental sciences the University of Virginia´s College of Arts & Sciences.

Kirwan and study co-author Simon Mudd, a geosciences researcher at the University of Edinburgh in Scotland, used computer models to predict salt marsh growth rates under different climate change and sea-level scenarios.

These salt marshes are acting as a sort of fail-safe measure for our environment. Consisting primarily of grasses, the salt marshes are vital to coastal ecosystems as they help to protect shorelines from storms. Additionally, they provide a necessary habitat for a diverse range of wildlife, including birds, mammals, fish and mollusks. Additionally, by trapping sediment during flooding, they act to build up the elevation of coastal areas and produce new soils from decaying organic matter and root structures.

"One of the cool things about salt marshes is that they are perhaps the best example of an ecosystem that actually depends on carbon accumulation to survive climate change: The accumulation of roots in the soil builds their elevation, keeping the plants above the water," Kirwan explained.

Salt marshes are repositories for enormous quantities of carbon. These stores of carbon are essential to plant productivity. The plant life, breathing in the atmospheric carbon, utilizes that transaction to facilitate growth. As plant life flourishes, it aids in increasing the overall height of the soil. Even if the grass were to die, carbon remains trapped in the sediment.

The model proposed in the study explains that even with a rise in sea-level, the marshes could bury up to four times as much carbon as they currently do.

"Our work indicates that the value of these ecosystems in capturing atmospheric carbon might become much more important in the future, as the climate warms," Kirwan said.

The good news does come with a caveat. The marshes can only survive if the rising sea-level occurs incrementally. If, as many climate scientists believe, the tipping point has been passed or is fast approaching and global sea-levels rise at a rapid rate, the marshes would be unable to increase their elevations quickly enough to keep pace, leaving them unable to act as a carbon storage ecosystem.

"At fast levels of sea level rise, no realistic amount of carbon accumulation will help them survive," Kirwan noted.