U of M researcher finds even minimal warming could devastate northern forests
Even relatively small amounts of global warming could spell disaster for the earth’s most northern forests, according to new research led by a University of Michigan ecologist.
Boreal forests contain mostly spruce, fir, and pine trees. They’re mostly located in Canada and Alaska, but are also found in small parts of the northernmost U.S., including a slice of Michigan’s Upper Peninsula.
Using infrared lamps and soil heating cables, a team of University of Minnesota researchers working under Peter Reich, who’s also the director of the Institute for Global Change Biology at the University of Michigan, artificially warmed thousands of boreal tree species in outdoor sites over the course of several years. They also used tarps to vary the amount of rainfall the trees received.
Reich said it’s been known for some time that these “far northern forests have shown a lot of species that aren't doing well. But because so many things are changing at once, including temperature and rainfall and nitrogen pollution and carbon dioxide levels and fires, it's hard to know exactly what’s driving the decline.” This experiment was an attempt to pinpoint that.
The results they described were dramatic — and disturbing. Even with a relatively modest temperature increase of 1.6 degrees Celsius — just under 3 degrees Fahrenheit — survival rates for the most common boreal species were “much poorer, and their growth was much poorer,” Reich said. “We’re talking about 10, 20, 30, 40% lower survival and lower growth rates, which is pretty astounding.”
Reich said the researchers found the dramatic level of impact from that level of warming surprising, and a warning sign of what’s ahead if the world doesn’t act very quickly to contain climate change. And it’s not only because the boreal forests themselves would quickly become impoverished. “We rely on these forests for timber production, also for climate regulation by scrubbing carbon dioxide out of the atmosphere,” Reich said. “It’s also a home for other biodiversity.”
The researchers also examined the impact of warming on some other tree species such as oaks and maples, which are more common in temperate forests, and found the impacts were far less dramatic, in some cases even beneficial. However, Reich said it will take a long time for those species to colonize the boreal forest areas, leading an interim period of sparse and impoverished forest. In the meantime, invasive species such as the shrub buckthorn, which Reich said is neither ecologically or economically beneficial, will quickly start to colonize the boreal region.
Reich said the moral of the story is that we need to move off fossil fuels and onto renewable energy sources quickly — within the next decade — to avoid devastating the world’s boreal forests, and mitigate the worst effects of climate change.