The Wild Side: Climate change and our native species
In March 2010, I had the honor of being selected as one of the representatives of the Wisconsin Department of Natural Resources at the 75th North American Wildlife and Natural Resources Conference in Milwaukee. I spoke with a biologist from Maine, who shared that there is a fair likelihood that moose would be gone from the state within 30 years. Moose are just one example of victims of a changing climate. In this second installment of my doomsday series about wildlife and climate change, we will look at the impacts of climate change through direct and indirect effects.
Unlike animals that die when winters become too cold, moose cannot survive when overwinter temperatures are not cold enough. When I worked in southwestern Minnesota, we would get one or two reports a year of moose on a dead run south. These animals suffer from a parasite called brainworm, which was what we presumed to be the cause of this behavior. The brain short-circuits and the animal takes off, running over or through anything in its way. This parasite is eventually fatal. Another parasite, deer ticks, can actually drain enough blood from a moose to weaken it to lethal levels in a mild winter.
Climate change will create living conditions and habitat changes that may benefit some wildlife species, but become unlivable for others. Native wildlife species may feel direct negative impacts of the weather, like dying of exposure, heat, disease or thirst. Indirect impacts can also lead to wildlife demise. For example, the weather may warm earlier in the spring, causing birds to head north and hatch a brood of young too early. The insects they need to feed their young may not have emerged yet, and there is not enough food for the fledglings. However, this strategy could benefit resident birds, like chickadees and cardinals, leading to an increase in their populations.
The change in climate has also benefitted exotic invasive species, a threat to our own wildlife, fish and plants, what we refer to as flora and fauna. The National Wildlife Federation estimates 40 percent of threatened and endangered species are at risk primarily because of invasive species. Animal and plant species from other climates are already spreading in Wisconsin. Spotted knapweed, for example, has worked its way well north in the state. It secretes a chemical into the soil that is toxic to other plants, what we call allelopathy. This plant displaces native plants, and as temperatures become more moderate, this plant and others can advance north.
Meanwhile, native plants that require cooler winter temperatures could fade from the landscape. The paper birch, for example, is very vulnerable to climate change, and we could see it virtually disappear from Wisconsin in the next half century. The U.S. Forest Service Northern Research Station has put together a Climate Change Atlas for 134 Tree Species of the Eastern United States (nrs.fs.fed.us/atlas/tree/). It shows the paper birch numbers will be dramatically reduced in Wisconsin under most climate change scenarios. Our most vulnerable species also include quaking aspen, sugar maple, red maple and northern red oak.
What will happen to some of our common wildlife species when aspen and birch begin to die off? Many bird species, both game species (like ruffed grouse) and non-game species (like golden-winged warblers) rely heavily on this forest type. To survive, the birds will either need to adapt to the new climate or travel further north where their tolerances can be met. Ruffed grouse do not migrate or travel long distances. Under a “worse case” scenario, their numbers would slowly decrease until the population becomes too small to sustain. Without their main food source, and without adequate snow cover for protection from wintertime predators, grouse populations suffer; we already see this in states further south. If the climate continues to change as it has, it is possible that by the end of the century, grouse might thrive only in the northernmost reaches of the state.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR in Rhinelander and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.