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Is Climate Change To Thank For Dramatic Recovery Of Acid Rain's 'Canary In The Coal Mine'?

Sam Evans-Brown

Paul Schaberg marshals a small team of scientists, surveying a stand of red spruce in Colebrook for frost damage from last winter.

“So what are you guys seeing, are you seeing any injury yet?” he calls out.  

“We’re just seeing green needles,” hollers back one of his helpers.

“Happy, happy trees,” responds another.

There’s a dramatic recovery underway in New England. Red spruce, a tree species that researchers thought was doomed because of acid rain, is now growing faster than ever, and it’s not the only tree growing like gangbusters. The story of the red spruce hints that with a changing climate, there will be some species that are winners while others are losers.

Canary in the Acid Rain Coal Mine

Red spruce used to be a very high-value timber crop in the US, and still is in Canada, but from 1965 to 1986 it declined by around 65 percent.

The biggest reason? Acid rain. Schaberg says Red Spruce was the "canary in the coal mine" that showed the problems acid rain was causing.

The acidity was basically weakening the tree’s needles, so they would freeze off during the winter. With no new needles, the trees would get weaker and eventually die.

Credit Sam Evans-Brown / NHPR
Researchers discovered acid rain by measuring rainfall and runoff in brooks like this one, in the Hubbard Brook Research Forest in Thornton and Woodstock.

“When it’s very cold even the buds will die,” says Schaberg,” So you can see the little bud in there. “Which means not only will you lose the foliage, but you lose the new shoots that were coming from those buds.”

Researchers first stumbled onto acid rain in 1963. A little farther South at a place called at a place called Hubbard Brook, between Thornton and Woodstock. Schaberg is with the US forest service and was not one of those scientists, but the discovery shaped his career.

“Researchers at Hubbard Brook started to measure the pH of the rain in their samples, and realized these are really acidic. This is like lime juice; water shouldn’t be like this!” Schaberg explains.

Acid rain became a big headline in the early seventies, but then says for ten or so, many people sort of forgot about it.

“Until then things started happening,” says Schaberg, “Things like marble monuments in cemeteries melting away. Things like, literally, infrastructure degrading. And then things like trees starting to die mysteriously.”

Congress Steps In

But the story doesn’t end the way many feared it would.

“There has been a very major decline in precipitation pH,” says Gene Likens, who perhaps knows acid rain better than anyone.

He led the team that found acid rain at the Hubbard Brook research forest here in New Hampshire. He also helped establish the baseline for what rain pH should be by measuring acidity for ten years in remote places all over the globe, and link acid rain in the Northeast, to power plants upwind.

“We actually tried to follow, in small airplanes and vehicles on the ground, plumes from the Midwest,” Likens remembers.

Likens and other scientists briefed President Reagan on the issue, kicking off the political process that led to amendments to the Clean Air Act in 1990.

Credit Sara Plourde Data: / NHPR
Measurements of the basal area (size of the trunk near the bottom) of red spruce have shot up in recent years, and while climate change is near the top of the list of theories for why, scientists have yet to determine how much of the growth is due to warmer temperatures and more CO2.

“So it took a long time,” he says, laughing, “From 1963 to 1990.” Likens says he sees echoes of the effort to get acid rain under control in the current fight over climate change.

Likens is still following pH levels and he says we’ve come a long way; the rain is about 3 or 4 times less acidic than it was.

“But we’re still two or three or four times more acid than we should be if the atmosphere were not polluted,” he emphasizes.”

And there seems to be a payoff, here in the Northeast, for species like red spruce. Although, another acid rain poster-child – the sugar maple – isn’t out of the woods yet.

Rebound for Some, Stagnation in Others

Acid rain hurts the sugar maple by dissolving minerals in the soil it needs, compared to red spruce which is primarily damaged by acid droplets hitting the needles. It’s estimated that over the decades around fifty percent of these minerals washed away.

To get an idea of how important these minerals are, in the late nineties scientists at Hubbard Brook used helicopters to seed a whole swath of forest with calcium.

“We actually added back a little more than what was depleted,” says Likens.

Fifteen years later, sugar maple was the tree that saw the strongest rebound in the treated area. In the untreated forest, it continued to struggle.

In other words, some trees need more than just less acidity to bounce back. But as acid rain has declined red spruce has done more than just recover.

Thanks to tree rings, there’s a 200 year record of how fast red spruce grows, and they are “growing better than they ever have in the recorded history,” says Schaberg, “Trees now are growing twice as well as their maximum ever.”

Schaberg and his collaborators are trying to think up studies that will determine where that growth is coming from. How much is due to less acid, and how much is due shorter winters, less frost, and warmer temperatures?

Yes, We’re Talking about Climate Change

And yes, in this case it could be having a positive impact.

“Now each of these factors – extra CO2, warmer temperatures, and longer time to grow – are all known to enhance the growth of trees,” says Geoff Parker with the Smithsonian Environmental Research Center.

Parker did a study that found the growth rates for forests all up and down the eastern seaboard are picking up. However, even within the forests that are growing faster, some species are winners and others are losers.

“It’s pretty clear that forests are growing faster but I don’t know if anyone’s done a good job of looking [globally] at the species effect,” says Parker.

Credit Sam Evans-Brown / NHPR
Josh Halman surveys red spruce for signs of "winter injury" or dead needles and buds caused by cold temperatures hitting needles weakened by acid rain.

Scientists do think that in some areas, climate change will mean more droughts, which would be tough on some trees, and others don’t tolerate heat well. But Red Spruce – which many researchers thought was doomed – seems to be one of the winners, and it’s getting the climate boost on top of the benefits of less acid rain.

Back in Colebrook, amidst the stand of spruce, Schaberg and his collaborators say it’s a rare case of seeing the results of their work in their lifetime.

“It’s kind of a good-news-that-science-matters, kind of story, because the science…” begins Schaberg before Gary Hawley, another scientist from the University of Vermont, finishes his sentence, they used science to inform the public and made adjustments in pollution levels and it worked.”

After a moment Schaberg grins and adds, “and it’s kind of cool,” and both men chuckle.

And if faster growing forests are part of New England’s future, that seems okay too.

Sam Evans-Brown has been working for New Hampshire Public Radio since 2010, when he began as a freelancer. He shifted gears in 2016 and began producing Outside/In, a podcast and radio show about “the natural world and how we use it.” His work has won him several awards, including two regional Edward R. Murrow awards, one national Murrow, and the Overseas Press Club of America's award for best environmental reporting in any medium. He studied Politics and Spanish at Bates College, and before reporting was variously employed as a Spanish teacher, farmer, bicycle mechanic, ski coach, research assistant, a wilderness trip leader and a technical supporter.
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