Remember acid rain? In the 1970s and ‘80s, scientists found that rain 100 times more acidic than normal was harming the mountain forests of New England and New York.
The pollution was linked to fossil fuel plants in the Midwest. Now, a new study shows red spruce trees are recovering thanks to tighter pollution laws.
Researchers say this environmental success story shows the value of science in shaping public policy.
On a steep slope in the Green Mountains, forest researcher Alexandra Kosiba does a kind of medical exam on a towering red spruce.
She uses a long, drill-like instrument to extract a narrow slice of tree, all the way into the core. It makes a rhythmic clicking sound as it cuts through the wood.
Kosiba draws out the cutting slowly, and you can see the growth rings marked by dark and light bands. The sample backs up what Kosiba and her colleagues observed in a recent study of red spruce in five northeastern states: After decades of decline, the trees are healthy again.
“It looks like the recent growth is quite large, and if you go back a decade they start getting a lot smaller, and then even another decade they’re really tiny; they're incredibly small,” she said.
Indeed, three decades ago the news was pretty grim: Millions of trees like this one were dying, their needles red and their growth stunted.
The reason was acid rain.
It’s caused when pollutants released by fossil fuel plants downwind of New England chemically combine with precipitation and leach calcium out of the soil. The calcium depletion doesn’t directly kill the tree but makes them susceptible to stress and injury from cold winters. As recently as 2003, a deep freeze injured red spruce trees around New England.
“Sixty-five percent or more of the current year foliage died that year,” said Paul Schaberg, a U.S. Forest Service scientist who has studied the spruce decline.
Schaberg said that stark images of dead and dying red spruce forests in New England helped build the case for the 1990 Clean Air Act. That law, signed by President George H. W. Bush, limited emissions of sulfur dioxide and nitrogen dioxide, the precursors of acid rain.
Today, the recovery is impressive.
“It’s real; it’s recent, and it's broad scale,” he said.
Schaberg worked with Ali Kosiba on the recent research and has studied acid rain and forest decline for decades.
“It’s a great scientific arc of monitoring, doing scientific research, informing policy, monitoring some more, and with some great surprises like Ali’s work showing this rebound in a species that was the epitome of an impact,” he said.
Patrick Parenteau, who teaches environmental law at Vermont Law School, said the years of research help prove the value of science in shaping environmental policy.
“It doesn’t get any better than that. That’s environmental law and policy at its best,” he said.
Parenteau said it’s an important point to remember as some in Congress and in the Trump Administration question the science behind climate change research.
“Science is the key, getting that information into the public debate, and basing decisions on fact, not myth,” he said. “That’s critical.”
Developing the science around acid rain and its environmental took years.
Gene Likens first documented acid rain in the 1960s at the Hubbard Brook experimental forest in New Hampshire. Now in his 80s, Likens says the rain, snow and mist is 80 percent less acidic at that forest than at its highest levels 50 years ago. He says those early studies provided the groundwork for the 1990 Clean Air Act.
"And that’s what science does," Liken said. "We ask questions and look for answers to those questions and then try to communicate that information to decision makers in hopes that actions can be taken."
While the red spruce recovery is good news, other species like sugar maples growing on calcium poor sites are still threatened.
Other parts of the ecosystems — such as higher altitude lakes in the Adirondacks — are still too acidic.
And part of the reason the red spruce are doing better is warmer winters due to climate change. But researchers say that northern forests will likely suffer in the long run as the region continues to heat up.