Dead trees spell trouble for global environment

Scientists claim increase in 'ghost forests' most visible sign of crisis

PORT REPUBLIC, New Jersey - They're called "ghost forests" - dead trees along vast swaths of coastline invaded by rising seas, something scientists call one of the most visible markers of climate change.

The process has occurred 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 underway worldwide to determine exactly how quickly the creation of ghost forests is increasing. But scientists agree 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 the 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."

It is happening around the world, but researchers say new ghost forests are particularly apparent in North America, with 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 runoff, to contribute to algae blooms and reduced oxygen that can sicken or kill fish.

"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."

The ghost forest acceleration comes as scientists on Monday said that world temperatures are likely to rise by more than 2 C this century, surpassing a "tipping point" that a global climate deal aims to avert.

A study published in the journal Nature Climate Change shows a 90 percent chance that temperatures will increase this century by 2 to 4.9 C.

Researchers at the University of Washington found only a 5 percent chance that warming could be at or below 2 C - one of the targets set by the 2015 Paris climate deal on limiting emissions of greenhouse gases that warm the planet.

Missing that target would have dramatic consequences on people's livelihoods - such as prolonged periods of drought and rising sea levels - said Adrian Raftery, the lead author of the study and a professor at the university.

The study uses statistical projections based on total world population, GDP per capita and the amount of carbon emitted for each dollar of economic activity, known as carbon intensity.

"Our analysis shows that the goal of 2 degrees is very much a best-case scenario," said Raftery. "It is achievable, but only with major, sustained effort on all fronts over the next 80 years."

Ap - Reuters