Less acid rain helps red spruce bounce back

Im­ages of trees in­spired changes to Clean Air Act

Sun Sentinel Broward Edition - - Nation & World - By Lisa Rathke

STOWE, Vt. — The gray trunks of red spruce trees killed by acid rain once heav­ily scarred the moun­tain forests of the North­east. Now those forests are mostly green, with the crowns of red spruce peek­ing out of the canopy and saplings thriv­ing be­low.

A main rea­son, sci­en­tists say, is a govern­ment-en­forced re­duc­tion in the kind of air pol­lu­tion that trig­gers acid rain.

“We’ve seen it go full arc from de­clin­ing for some un­known rea­son, to fig­ur­ing out the rea­son, to them do­ing some­thing about the cause and then the tree re­spond­ing and re­bound­ing again,” said Paul Sch­aberg, a plant phys­i­ol­o­gist with the U.S. For­est Ser­vice and a coau­thor of a new study on red spruce who has been re­search­ing the species since the 1980s. “It’s just an amaz­ing sci­ence arc.”

In the 1960s through the 1980s, pol­lu­tion — mostly from coal-pow­ered plants in the Mid­west and car emis­sions car­ried by the wind and de­posited as acidic rain, snow and fog — dev­as­tated North­east forests and lakes, leach­ing nu­tri­ents from soil and killing aquatic life.

Red spruce are par­tic­u­larly sen­si­tive to acid rain and, at the height of the die­off, some forests lost 50 per­cent of them.

But decades later, not all the en­vi­ron­men­tal dam­age is turn­ing around at the pace of the red spruce.

Wa­ter­ways are show­ing signs of re­cov­ery, as are the up­per lay­ers of soil, al­though they are still strained by the acid de­posits. Re­searchers are find­ing fish in lakes deemed fish­less for years, but the pop­u­la­tions are not large and the va­ri­ety of species is not as di­verse as be­fore, said Gre­gory Lawrence, a re­search sci­en­tist with the U.S. Ge­o­log­i­cal Sur­vey who is based in Troy, N.Y.

In the 1980s, Univer­sity of Ver­mont sci­en­tist Hu­bert Vo­gel­mann brought na­tional at­ten­tion to the acid rain is­sue by link­ing air pol­lu­tion to for­est dam­age on the slopes of Ver­mont’s Green Moun­tains.

Air­borne chem­i­cals re­acted with wa­ter and oxy­gen and then, car­ried by the wind, were de­posited as acidic rain, snow and fog.

The im­ages of dead trees lit­ter­ing moun­tains in the 1980s helped in­spire changes to the Clean Air Act in 1990. The amend­ments pro­posed by Pres­i­dent Ge­orge H.W. Bush in 1989 man­dated re­duc­tions in cer­tain gas emis­sions and boosted reg­u­la­tion of toxic pol­lu­tants.

The first signs of health­ier red spruce trees in the north­east­ern U.S. came five years ago, sci­en­tists said.

The re­searchers ex­am­ined 658 red spruce trees in 52 plots in Ver­mont, New Hamp­shire, New York, Mas­sachusetts and Maine.

They found that 75 per­cent of the trees and 90 per­cent of the plots showed in­creas­ing growth since 2001. They credit cleaner air and a warm­ing cli­mate that ex­tended the grow­ing sea­son.

“Higher tem­per­a­tures help some species and hurt oth­ers — right now, red spruce are ben­e­fit­ing, but they could be vul­ner­a­ble to change in the fu­ture,” Sch­aberg said.

Sim­i­lar trends are emerg­ing in the Ap­palachian Moun­tains in West Vir­ginia, which were also hit by acid rain, ac­cord­ing to a re­cent re­port in the Global Change Bi­ol­ogy jour­nal.

The two stud­ies pro­vide fur­ther ev­i­dence that ad­dress­ing causes of acid rain helped the species re­cover, said Ti­mothy Fa­hey, a for­est ecol­o­gist and pro­fes­sor at Cor­nell Univer­sity.

That re­cov­ery should help ef­forts to re­store red spruce forests to moun­tains in cen­tral Ap­palachia, where they were heav­ily logged in the late 1800s and early 1900s, re­duc­ing the habitat for the now-en­dan­gered Carolina north­ern fly­ing squir­rel.

Last month in Ver­mont, Sch­aberg was hik­ing through the woods on Mount Mans­field, Ver­mont’s high­est peak, with Alexan­dra Kosiba, lead re­searcher for their study in the jour­nal Sci­ence of the To­tal En­vi­ron­ment.

They found red spruce at mid­dle el­e­va­tions and higher that were thriv­ing.

“This is a good sign that the species is do­ing well in the near term, and then the fu­ture forests will have red spruce,” said Kosiba, a staff sci­en­tist for the For­est Ecosys­tem Mon­i­tor­ing Co­op­er­a­tive at the Univer­sity of Ver­mont.


U.S. For­est Ser­vice sci­en­tist Paul Sch­aberg stands be­side a healthy red spruce tree grow­ing on Mount Mans­field in Stowe, Vt.

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