Eric Douglas Published

Research Reveals Clean Air Makes Stronger Forests

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Air pollution can actually cause forests to grow faster, as the nitrogen in acid rain is a fertilizer. The problem is, it makes the trees weaker and more susceptible to storm damage.

That’s according to West Virginia University postdoctoral researcher Chris Walter’s research into the subject. His research was made possible by the coincidence of a localized storm that hit directly on top of a forest research project. Walter’s paper was recently published in the journal Forests and he spoke with Eric Douglas to explain what it all means for West Virginia.

This interview has been lightly edited for clarity.

Douglas: Explain the unique nature of how you were able to do this study in the first place.


Courtesy photo
WVU researcher Chris Walter

Walter: At the Fernow Experimental Forest, they do a lot of research. It’s right outside of Parsons, West Virginia. And it’s located within the larger Monongahela National Forest. In 2009, there was a storm event with a microburst. It really only affected one side of the mountain. And it really hammered that area. And so we thought, maybe there’s some effects. We know there’s effects of acidification on trees and whether they make stronger or weaker wood. We know they grow taller, potentially, with more nitrogen. I thought maybe there’s some effects of this storm that we could test.

Douglas: What did you find when you studied what happened with the storm event?

Walter: Generally, across all the tree species that we studied, we saw that about 10 percent more trees were damaged by the storm overall. That was across all species. But when we looked a little closer at some of the species, particularly black cherry, which is a pretty high value timber species in our region, somewhere between 15 percent to 25 percent more trees were damaged in those treatments. Overall, we saw that any one tree would be damaged more. And then finally, there was this category of damage, where we rated the angle of the tree after it was damaged. If the tree was basically parallel to the ground, that was a pretty catastrophic event, whether it was snapped or bent over. So, what we found was that anywhere from 10 percent to 31 percent of these trees in the fertilized area were catastrophically damaged and weren’t going to grow back.

Douglas: What does this experiment tell us from what you’re seeing in the real world?

Walter: There’s two things that I think might be interesting. One is that our areas received historically high levels of this type of pollution. And so I think that we already have a good number of acidified forests in central Appalachia. We can somewhat argue that we’re already at elevated risk from our history of this type of pollution. That’s one aspect of it that I think is pretty interesting.

The second is that this fertilization is a ‘what if’ scenario. So, if we didn’t make the Clean Air Act Amendments of 1990, we would have continued on this trajectory of continual pollution. And so we can also use this and say if we hadn’t controlled our pollution levels, we would expect this type of damage to continue. It’s an argument that the Clean Air Act, amendments, may be making our forests more resilient.

Douglas: Those changes we made 30 years ago may have actually saved some of our forests and put them in better shape moving forward.

Walter: Absolutely and we see that in other research, too. There’s another group at West Virginia University that studies high elevation spruce. And they’ve seen a very large rebound in growth and vigor of trees. And so this aligns with that work. We’re making more vigorous and resilient forests, because we’re not fertilizing them. The final thing is there’s temperate forests similar to ours all over the world. One of the largest regions is China. And so there are areas in China outside of major cities that are polluting at rates that we never even experienced in America and basically fertilizing their forests at rates that you might expect in fertilized corn if you’re a farmer. There’s areas of the world that could be at risk of greater Storm Damage as well.

Douglas: We’re seeing situations with more extreme storms, more extreme weather events. How does that play into West Virginia forests moving forward?

Walter: The frequency of large magnitude storms is growing larger with climate change, mostly because the ocean is warming. There was a great paper that came out last year in Science. This paper showed that hurricane intensity after they reach landfall, they’re more powerful. They’re slower to decay in their power. All signs indicate that we’re going to be at more risk for damage from these types of storms, even in West Virginia.