Thu | Aug 17, 2017

Climate change before your eyes: Seas rise and trees die

Published:Wednesday | August 2, 2017 | 8:00 AM
This July 16, 2017 photo shows a 'ghost forest' near the Savannah River in Port Wentworth, Georgia.

PORT REPUBLIC, New Jersey (AP):

They're called 'ghost forests' dead trees along vast swathes of coastline invaded by rising seas, something scientists call one of the most visible markers of climate change.

The process has happened naturally for thousands of years, but it has accelerated in recent decades as polar ice melts and raises sea levels, scientists say, pushing salt water farther inland and killing trees in what used to be thriving freshwater plains.

Efforts are under way worldwide to determine exactly how quickly the creation of ghost forests is increasing. But scientists agree that the startling sight of dead trees in once-healthy areas is an easy-to-grasp example of the consequences of climate change.

"I think ghost forests are the most obvious indicator of climate change anywhere on the eastern coast of the US," said Matthew Kirwan, a professor at Virginia Institute of Marine Science who is studying ghost forests in his state and Maryland. "It was dry, usable land 50 years ago; now it's marshes with dead stumps and dead trees."

 

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It is happening around the world, but researchers say new ghost forests are particularly apparent in North America, with hundreds of thousands of acres of salt-killed trees stretching from Canada down the East Coast, around Florida and over to Texas.

The intruding salt water changes coastal ecosystems, creating marshes where forests used to be. This has numerous effects on the environment, though many scientists caution against viewing them in terms of "good" or "bad." What benefits one species or ecosystem might harm another one, they say.

For instance, migratory birds that rely on coastal forests have less habitat. And the death of the trees makes soil microbes release nitrogen, which adds to nitrogen already occurring from other sources, including agricultural run-off, to contribute to algae blooms and reduced oxygen that can sicken or kill fish.

Two sides of the climate change coin

The conversion of forest into marshland produces "extremely productive" wetlands that feed and shelter fish and shellfish.

The Atlantic croaker fish, for instance, was rare 15 years ago in southern New Jersey waters but now is abundant, said Ken Able, a Rutgers University professor.

"There is a lot of change going on," said Greg Noe, a research ecologist with the US Geological Survey. "It's dramatic and it's changing faster than it has before in human history."

Quantifying the rate of increase in ghost forests is a major focus of Able's research. Some scientists say the increase began around the time of the Industrial Revolution, while others say the speed-up began more recently than that.

In the past 100 years, Kirwan said, 100,000 acres of forest in the Chesapeake Bay have converted to marshland. Photographs show the rate of coastal forest loss is four times greater now than it was during the 1930s, he said.

Seas off the East Coast have risen by 1.3 feet over the last 100 years, said Ben Horton, a Rutgers University professor and expert on sea level rise. That is a faster pace than for the past 2,000 years combined, he said.