Climate Change Pushing Northern Forests

  • Chris Swanston during a training event for the Adaptive Silviculture for Climate Change (ASCC) project on the Chippewa National Forest in Minnesota, 2013. Photo: Courtesy Michigan Technological University

September 26, 2014

Climate change is throwing a wrench into northern U.S. forest ecology, where invasive earthworms are increasing drought stress and native trees are increasingly being pushed to northern climes faster than they can move. Researchers like Chris Swanston with the U.S. Department of Agriculture’s Forest Service are working on an adaptation strategies. The Allegheny Front’s Jennifer Szweda Jordan spoke with Swanston in Chicago where he was speaking at the Metcalf Institute for Marine and Environmental Reporting. Below are some of the highlights of their interview.

Earthworms can be bad?

Whoever thought of earthworms as megafauna or as anything other than wonderful in dark, rich, loamy soil in your garden. But in forests, in the Northwoods, it’s a little bit different, because we haven’t had worms in these forests since the last Ice Age, before the last Ice Age. What you get then is soils forming after the glaciers went away, without earthworms. So earthworms come in, they do the same thing they do in your garden, which is they mix up the soil. But as they mix up the soil, they take all of that wonderful forest floor, the duff that’s on top of the mineral soil, and they mix it in. And one of the things that that does is it actually changes the way that the soil hold moisture. And it changes the way that plants actually can root in the soil. Now they’re rooting in mineral soil, which is drier. And one of the things that’s doing is it;s changing the type of plant that grows in our northern forests. It’s also exposing bare mineral soil to heavy rains that we’re getting more often with climate change. And that can cause erosion as well.

Reasons for increased fire risk in northern forests

One of the things that we’re considering as the climate changes and the forests respond, is that these forests is that these forests have changed dramatically over the last 150 years. Humans came, they cut down what was there, it was replaced with oftentimes a different type of forest, one which is much more water-loving and also water-needing. And so, as climate change continues, and a lot of this region will effectively dry out—and I want to make a point that we have been getting more moisture, in fact we expect to get more precipitation as time goes by, but what is really critical is the precipitation that the plant experiences during its growing season. And so, if more of that rain, for example, comes in the form of giant events, and then you have longer dry periods between those events, one of the things that can happen is that these trees can experience water stress. One of the things that the worms do is that they cause the soil to be drier, and then these plants need somewhat more water potentially than is there anyway, with the changing climate, and so all of this can lead to a greater fire risk.

Approaching diverse forest owners about the touchy subject of climate change

The bottom line is we meet people on their terms, and what’s critical is that we ask them what their goals are, what their views of their land are, what their needs are, before we really ever start talking about climate change. And then our goal is to help them meet their goals. We’re there to bring climate to the table, to talk about the pressure it may place on the ecosystems that they manage on their land, and about risk that’s associated with those pressures. And ultimately the decisions are theirs.

Innovative approaches to climate change and forests

Menominee Tribal Enterprises in northern Wisconsin, they have struggled over the past years with an oak wilt outbreak. And one of the things that happens is the oak wilt comes in of course and it kills the oaks, and one of the ways to deal with this is to essentially take out the oaks that are there, and then a buffer strip all around that. And when you look at the aftermath of all of this it looks kind of like a moonscape. And this is kind of what you need to do to get rid of this disease. And so then the question becomes, what do you put back? As the Menominee look at this question, they think seven generations ahead, just as they think seven generations in the past, and their responsibility is to maintain a diverse forest that meets the needs of the tribe—the cultural needs as well as the economic needs. Some of these species aren’t what’s there now, and they’re essentially bringing them in from other parts of the country.

What the Ottawa National Forest is doing is they’re looking at the potential strain that climate will place on the reproduction of species that are there now, and they’re trying to reprioritize some of their activities to ensure that as climate change advances and accelerates, that they have the most land available and healthy plant species to support wildlife as they can get.