Cli­mate change be­fore your eyes

Seas rise and trees die

Cape Breton Post - - Perspective - BY WAYNE PARRY

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 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 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 U.S.,” 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.”

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 runoff, to con­trib­ute to al­gae blooms and re­duced oxy­gen that can sicken or kill fish.

But 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 U.S. 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 speedup be­gan more re­cently than that.

In the past 100 years, Kir­wan said, 100,000 acres of for­est in the Ch­e­sa­peake Bay has 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.

Some of the most dra­matic anec­do­tal ev­i­dence of the ac­cel­er­a­tion in ghost for­est creation is along the Sa­van­nah River be­tween Ge­or­gia and South Carolina, Noe said.

When his team first got there 10 years ago, “it looked like the trees were un­der a lit­tle stress, but they were all alive,” he said. “But five years later, the vast ma­jor­ity of them were dead. That hap­pened right in front of our eyes, much faster than we ex­pected.”

Marcelo Ar­don, a bi­ol­ogy pro­fes­sor at North Carolina State Univer­sity, stud­ied one site called the Pal­metto Pear Tree Pre­serve on Albe­marle Sound in North Carolina from 2006 to 2009. When he re­turned in 2016, he said, “what used to look like a healthy cy­press swamp, now the trees are dead and the wa­ter level is a lot higher. The place has com­pletely changed. I’ve checked over­head satel­lite pho­tos and you can see the trees dy­ing.”

In south­ern New Jersey, the most af­fected species is the At­lantic white cedar, which was a main­stay of the ship­build­ing in­dus­try be­cause of its re­sis­tance to rot. Far­ther south, cy­press, loblolly pines and Eastern red cedar are dy­ing.

Large storms can drive salt wa­ter fur­ther in­land and kill trees; 2012’s Su­per­storm Sandy is be­lieved to have led to the deaths of some trees in south­ern New Jersey, Able said.

The dif­fer­ence, Kir­wan said, is that in the past, flooded ar­eas would dry out be­fore salt wa­ter killed most of the trees.

“That same storm 100 years ago would also have killed trees,” he said. “But 100 years ago that same land wouldn’t have been so wet that new trees couldn’t get es­tab­lished and re­place the dead ones. That’s a big part of where sea level rise comes in.”

AP PHOTO

A nar­row band of brown pine trees that were killed by Oc­to­ber 2015 tidal flood­ing near York­town, Va.

AP PHOTO

This July 16 photo shows a “ghost for­est” near the Sa­van­nah River in Port Went­worth, Ga.

AP PHOTO

The sun rises on a ghost for­est near the Sa­van­nah River in Port Went­worth, Ga

AP PHOTO

Phrag­mites and Spartina marsh­land ex­pand­ing into a ghost for­est in Rob­bins, Md.

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