Climate change could doom Alaska’s tundra

In the next 100 years, Alaska will experience a massive loss of its historic tundra, as global warming allows these vast regions of cold, dry, lands to support forests and other vegetation that will dramatically alter native ecosystems, an Oregon State University researcher said today.

Polar regions such as Alaska will be among the first to illustrate the profound impacts of climate change, said Dominique Bachelet, an associate professor in the OSU Department of Bioengineering and expert on the effects of climate change on terrestrial vegetation. She spoke at the annual meeting of the Ecological Society of America.

More precipitation, an overall loss of soil carbon, a probable reduction in forest fires and a likely increase in insect and pathogen attacks on trees are also projected by some of the most sophisticated computer models yet developed, Bachelet said. “The effects of climate change in Alaska will be among the most visible in the world,” Bachelet said. “The tundra has no place else to go, and it will largely disappear from the Alaskan landscape, along with the related plant, animal and even human ecosystems that are based upon it.”

The newest research suggests that 90 percent of Alaska’s tundra that was present in 1920 will be gone by 2100, less than a century from now, under one of the climate models projecting the most extreme warming. A model with more conservative estimates indicates that 77 percent of the tundra will disappear during that time.

Temperatures have already been above the historical norm in Alaska for the past 17 years. But about 100 years from now, the average annual temperature in Alaska may soar up to 13 degrees Fahrenheit higher in the worst case scenario predicted by climate models. Tundra is a cold, comparatively dry ecosystem that now covers much of Alaska, characterized by the permanently frozen deep soil layers called permafrost, few or no trees, grasses and dwarf shrubs, and an extremely short growing season. But it also supports brown bear, wolf, wolverine, caribou, arctic hare, mink, weasel, and lemming, and millions of migrating waterfowl. In summer it can feature thousands of lakes and large marshy areas.

According to Bachelet, despite some of the criticisms aimed at them, climate models appear to work better and achieve higher accuracy over longer rather than shorter periods of time.

“If you ask these models to predict exactly what the global climate will be in the summertime five years from now, that’s much more difficult because of the natural, short-term variations in weather and climate,” Bachelet said. “But based on everything we’ve learned, when we predict what’s going to happen during a 20-year period about a century from now, we can be fairly confident. We also test these models by running them backward into the past, and the results are quite accurate.”

Bachelet and her colleagues at OSU and the U.S. Forest Service have developed the Dynamic Global Vegetation Model MC1, an improved way of predicting what certain climate scenarios will mean in terms in of vegetation growth, plant and soil processes, carbon storage or emissions, forest fire, and other important ecological effects.

The latest simulations with this model were done with Alaska as a prelude to work with much of the world’s Arctic region, Bachelet said. “Some of this is not that surprising, the winters in Alaska are already getting milder and the summers warmer,” Bachelet said. “Were already seeing glacial melting, movement in fish migrations, Inuits who are having to change their fishing and hunting habits because of melting ice.”

But any changes so far pale in comparison of what’s to come, and fairly soon, Bachelet said. Among the predictions:

• Boreal mixed forests could yield to a maritime and temperate conifer forest much like those of southeast Alaska, and cover huge areas of Alaska.
• The only large area of remaining tundra in Alaska 100 years from now will be on its north coast.
• Because of increases in precipitation and despite an increase in statewide biomass, forest fires should become less frequent overall and could shift from central Alaska to the northeast.
• Insects and pathogens, which can adapt more readily to changing environmental conditions, may cause massive epidemics of plant disease and insect attack – in some cases causing large forest die-offs that could then lead to more fires, adding complexity to the picture.
• The average annual temperatures in much of Alaska could increase by more than 13 degrees above a 1920-2000 average by the last decade of the 21st century, according to the most extreme climate scenario, and 8 degrees under a more conservative scenario.

There are some variables that could affect these projections, Bachelet said, such as major changes in ocean circulation patterns that could have unpredictable effects on regional climate. One such change that has been suggested – a shutdown of a major ocean current and circulation pattern in the North Atlantic ocean that currently is responsible for warming much of Europe – might have other ripple effects that would cause regional climate impacts to vary.

“You’ll always have some uncertainties when you are trying to predict the localized impact of global climate change,” Bachelet said. “But it’s pretty certain that our global climate is warming up, and at this time, it looks like one of the major impacts will be on the tundra ecosystem of Alaska.”