Study reveals calcium can reverse damage caused to trees by acid rain

Hubbard Brook Ecosystem Study/Courtesy

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A team of researchers from across the nation has discovered that calcium can restore tree deterioration caused by acid rain.

The study, which involved researchers from UC Berkeley, Cornell University, University of Michigan and Syracuse University, began 15 years ago when researchers noticed that trees in the Hubbard Brook Experimental Forest in New Hampshire stopped growing. The team hypothesized that the pause in growth was due to excessive amounts of acid rain, which had greatly impacted the environment since the 1960s.

“The goal was to make this important link that pollution or any kind of environmental stress can have lasting effects,” said John Battles, a UC Berkeley professor of forest ecology in the department of environmental science, policy and management who headed the publication of the research. “The take-home point is that this legacy of damage lingers in the forest.”

The study, released in the Environmental Science and Technology Letters journal on Sept. 19, confirmed loss in tree health was not due to natural causes but to long-term exposure to acidity and that the problem could be reversed with calcium. The researchers discovered that wollastonite, a naturally occurring soil mineral commonly used in whitening products, could provide the calcium that would restore tree health lost from decades of exposure to acid rain.

In 1999, the researchers dumped wollastonite pellets via helicopter into the watershed of the Hubbard Brook Experimental Forest in New Hampshire, a forest maintained by the U.S. Forest Department and dedicated for ecological research. The trees then absorbed the calcium over time, restoring nutrients lost from acid rain.

According to Battles, adding calcium to restore tree health is not yet a possible solution for widespread use. The experiment cost hundreds of thousands of dollars, Battles said.

However, groups like the U.S. Park Service, the U.S. Forest Service, the EPA and the state of New York have discussed the idea of adding calcium to acid-impacted trees — even though it currently stands as a last resort and decisions have yet to be made.

“People have objections to foreign things being added to a wilderness area, even though it’s a naturally occurring thing,” said Charles Driscoll, a professor in the department of civil and environmental engineering at Syracuse University who headed the research. “But it could be done. There’s no reason why it can’t be implemented on a wide scale. The only problem is that it costs money.”

According to Driscoll, adding calcium to forests, a process commonly known as liming, has been done on a very large scale in Sweden and Germany. Currently, the researchers are conducting liming experiments in the Adirondacks to recover native fish species.

According to Battles, developing countries like China, where a lot of acidity is produced from coal-producing power plants, could benefit from this type of solution. Battles said although this solution is not suitable for widespread use, it would be useful in places where acid rain harms more than just trees.

“They might use it on forests that are near water supplies, a forest in a national park or a historical preserve,” Battles said.

Driscoll gave a talk in China on Sept. 18 in which he shared his ideas on liming experiments. He said his ideas garnered a lot of interest there.

“The acid rain story is a real environmental success story,” Driscoll said. “The results have been huge.”

Contact Lydia Tuan at [email protected].