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BWCA blowdown and aftermath show how global warming is changing Minnesota: Prairies are replacing forests

Aerial view of Basswood Falls and river looking west circa 1980.
U.S. Forest Service/Minnesota Historical Society
Aerial view of Basswood Falls and river looking west circa 1980.

Last Saturday was too hot and muggy for a 30-mile bike ride. But since I was never the smartest kid in class, there I sat, dismounted, panting and sweating on a bench in Mears Park, thankful for a cold soda from the drink cart and all those tall, shady trees.

This is my favorite urban park in the Twin Cities, an island of green loveliness surrounded by some of St. Paul's most beautiful historic buildings. Yet on a day so sweltering, not even this spot could keep my mind from drifting toward cooler climes. I imagined the piney shores of Lake Superior and the sparkling lakes of the Boundary Waters before recalling Lee Frelich and his disturbing discovery about what's happening to Minnesota's north woods. It kind of took the edge off my daydream.


Remember the big blowdown of 1999? Starting on the afternoon of July 4, a massive derecho packing violent winds of more than 90 mph swept along the U.S.-Canada border for 1,300 miles. In all, the storm lasted 22 hours. It blew down nearly a half million acres of trees in the Superior National Forest, including about 40 percent of the trees in the Boundary Waters Canoe Area Wilderness.

For Frelich, director of the University of Minnesota's Center for Hardwood Ecology, the blowdown and its aftermath of fires and forest regeneration confirmed on a massive scale what he had long suspected: The new north woods growing up to replace the millions of blown down trees isn't really a north woods at all but something more akin to the grassland savannahs farther south. Indeed, over the last decade or so, the blowdown has become a giant laboratory for measuring the ecological effects of a warming climate and the role humans are playing in accelerating the change.

Prairie replaces forest
Most of the trees lost in the storm were pines and aspens, Frelich told me this week. By normal succession, they would be replaced initially by varieties of spruce, fir and cedar. But instead red maple, basswood and other species normally found farther south are sprouting on the forest floor. "Recently I was at Snowbank Lake near Ely and I was just amazed to see all the red maple coming up," he recounted.
 
Frelich admits that until the last few years his observations greatly depressed him. He loves the woods, after all. He grew up in the grip of Sigurd Olson's lyrical writings about the magic of the northern wilderness. To realize that Minnesota's thick, dark canopy of conifers would be replaced by, in Frelich's words, "a scrubby, species-poor landscape" was not a pleasant prospect. But he's no longer angry. He tries to see the blowdown in a broader perspective — as part of the paleo-ecological record and as an opportunity to gather more data to chronicle the changes ahead. He holds out little hope than humans will alter their carbon habits enough to prevent the intrusion of prairie into the forest.

A journal article to be published next month in Frontiers of Ecology and Environment further documents Frelich's findings. He and his U colleague Peter B. Reich, professor of forest ecology and tree physiology, explore likely changes over the next 50-100 years in the composition of northern forests due to global warming.

"Under a scenario of human-induced global warming, the prairie biome will shift to the northeast and displace existing forests," the paper declares. Here's a summary of its observations:

Think of Minnesota as having an ecological border running across it diagonally, northwest to southeast. To the northeast, boreal forests dominate the landscape. To the southwest, savannahs — prairies with small trees that do not close to form a canopy — prevail. Over the last million years, the border has shifted eight times, but this time is different; the conifer forests are retreating to northeast farther and faster than before because there are higher levels of carbon in the atmosphere (twice the pre-industrial concentration).

A perfect storm of events
Likely accompaniments to this ecological trend? A warmer, drier climate that outstrips the ability of tree normal species to keep pace with the change; a greater rate of evaporation; more severe wind storms; a greater number of severe fires that give warmer-climate plants a better opportunity to invade; more exotic insects and diseases affecting trees; an overabundance of deer that browse woody plants that would otherwise grow into trees; and the further invasion of earthworms that disturb the forest floor's ability to hold moisture. (As it turns out, nightcrawlers and angleworms, imported to use as fishing bait, are not native to Minnesota.)

"All of those factors are pushing the forest in the same [northeast] direction," Frelich told me. "My best guess is that the BWCA Wilderness will look more like a savannah than a boreal forest within five to 10 decades."

Altogether, he and Reich report in their writings an expectation that the lost of forest along the prairie-forest border of central North America could equal an area twice the size of California.

"There's no doubt that human activity has made this a unique, super-charged event," Frelich said.

Inpact on the urban landscape
Frelich describes what might be called an ecological reset. Higher levels of CO2 in the atmosphere have set off a chain of events. Plant life adjusts to changing conditions. Forest becomes prairie. Habitats change. Animals adjust.

Maybe it runs parallel to the reset taking place in the world of human settlement. Jim Erkel, land use and transportation director for the Minnesota Center for Environmental Advocacy, offers the analogy. Conditions for humans are changing. Not only do we have a warming climate and an unstable energy supply, we have a faltering economy and significant demographic shifts toward smaller households.

What's required is a reset, Erkel suggests, citing the Austrian economist Joseph Schumpeter's theory of "creative destruction."

Economic crises sweep away outmoded companies, practices and systems, clearing the way for entrepreneurs to introduce new technologies and new ways of doing things that reignite growth.

In that context, we can't build cities the same old way, Erkel said. Conditions require a spatial fix, a new development pattern that's more that's more compact and energy efficient. Some people will resist these changes, complaining about loss of basic freedoms, the rising price of gasoline or the falling values of large suburban homes, for example. But maybe, said Erkel, moral values aren't really involved. Maybe changes in the urban form should be viewed as similar to the ecological adjustments being made in Minnesota's northern forests.

"There is no right or wrong in the way nature resets itself to changing conditions," he said. "It's just the way it happens."


Related: Two articles by Frelich and Reich

Wilderness Conservation in an Era of Global Warming and Invasive Species: A Case Study from Minnesota's Boundary Waters Canoe Area Wilderness (2009)

Will environmental Changes Reinforce the Impact of Global Warming on the Prairie-Forest Border of Central North America?

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Comments (9)

This analogy between the economy and changing climate doesn't work. It's like if we destroy nature, something better will pop up in its place. Even in economics though, "creative destruction" is often just destruction, and the theory is pushed by economists divorced from the effects of their actions and with no worry they'll be among the losers. But at least that doesn't destroy the environment. We don't know what changes we're wreaking and the idea that magically the changes will be better is just crazy.

Good article. Please include more photos next time.

The real reason for the change is not the global warming hoax. When the storm blew down the trees the loggers in the area begged to go in and remove the dead trees as they warned if the blowdown was left in the forest it would present a great danger of fire. Removing the trees would have provided the loggers income would have helped the regrowth in the forest. The loggers where stopped from removing the dangerous dead wood by environmentalists. The great fire as predicted by the loggers devastated the forest and greatly influenced the area’s environment. THIS DEVISTATION CAN BE BLAMED DIRECTLY ON THE ENVIRONMENTALISTS AND THEIR NARROW MINDED POLICEYS.

Frelich describes what might be called an ecological reset. Higher levels of CO2 in the atmosphere have set off a chain of events. Plant life adjusts to changing conditions.

i wonder where mr frelich went to school. does he not know plants and trees thrive on Co2. higer levels of Co2 promotes greater plant growth. many greenhoused pump in C02 to promote greater plant growth. higher C02 level are not a hinderence to plant growth, it is their food.

I second Eric. As far as we can tell, the conifers will not feel pain nor shed tears as the conditions change and their continued existence becomes impossible. They will simply, quietly die to be replaced by whatever species are most suited to the new environmental conditions.

With us humans, however, there is pain and anguish associated with the massive movement of the source of our livelihoods being shifted to other places in the world, purportedly to give us lower prices, but, in reality, to further increase the incomes of the already fabulously wealthy owner, manager, investor classes.

Furthermore, although money is free to go anywhere in the world where it's owners believe it will give them the greatest rate of return, workers and NOT free to move to better economic climates - to wherever the quality of life offers THEM the greatest benefit for their labors.

If we reach the point where massive numbers of humans, even in the first world, die of starvation and entire regions of formerly-prosperous countries begin to crumble to dust (as is already happening in many of the major industrial cities of the US), it is not painless, nor is it unintended.

What has been done through the restructuring and deregulation of the US economy is tantamount to clear cutting the boundary waters in order to allow a few very wealthy farmers to gain even more wealth by clearing the way for their own farming schemes (which, by the way, is likely to attempted if the prime crop growing land is the central US turns arid as the result of global climate change).

It occurred to me, while reading Mr. Granneman's posts, that Denialists are rather like the proverbial frog in a pot. Everything is fine at first, and the frog is happy, swimming laps in the pot. As the water gradually heats up, the frog continues to think everything is alright - perhaps he even thinks the whole notion of frogs being cooked and eaten is a hoax. However, the heat doesn't care about what the frog thinks, and eventually the frog is cooked, denying there's a problem right up until the end.

Keep spouting your Denialist nonsense, Mr. Granneman, even while heat waves become ever more prevalent and severe, the oceans acidify, the waters rise, ecosystems are disrupted faster than the plants and animals can respond, and people suffer in ever greater numbers. I suppose that, when life on Earth has become rather hellish, you'll say the liberals engineered it all as part of their ongoing environmental hoax.

Who is it who needs to go to school?

hello mr groth
i see that like most environmentalists instead of discussing the merits of my post, you prefer to the same old name calling and fear mongering. the facts are that the earth's temperature has varied greatly in the past. 1000 years ago the time called by scientists THE MIDIEVAL WARMI PERIOD the earth was much warmer than today, so warm that the vickings where able settle and thrive in GREENLAND. records indicate that they were able to even grow grapes and farm in GREENLAND. today greenland is very much colder. 500 years ago scientists called the LITTLE ICE AGE. the earth was much cooler and these low temperatures where the cause of THE DARK AGE in europe. crops failures, starvation, and disease where common. thankfully, since then the earth has warmed up and made life better for the people of earth. as you can see mr. groth, GOD was much smarter than you environmentalists as he created a planet that is very robust and resilient and able to florish for the past 3 million years. mr groth instead of calling me names, WHY DONT YOU LOOK AT THE FACTS.

The problem here...

is that all instances are based on anecdotal evidence (and probably denier websites). The Medieval Warm Period was focused within the north Atlantic, hardly global. Now what caused this, at best you and I and everyone else can only speculate. Could it have been a change in oceanic currents? Possibly. As for the Little Ice Age and the The Dark Age, both have been attributed to volcanic eruptions and materials reflecting sunlight back into space. You could also cite The Year Without Summer in 1816, but that would also be attributed to the catastrophic explosion of Mt. Tambora. Mr. Granneman, if you can provide scientific evidence to contrary that would be wonderful.

For further reading I direct you here:
http://www.ncdc.noaa.gov/paleo/pubs/moberg2005/moberg2005.html

Your post avoids...

the preponderance of evidence demonstrating that CO2 has been known as a greenhouse gas for well over a century--and yes plants do require CO2 but that is beside the point. In 1861, John Tyndal published laboratory results identifying CO2 as a greenhouse gas that absorbed heat rays (longwave radiation). You can also find studies most notably from 1953 (G. Herzberg), 1962 (D. E. Burch), and 1970 (D. E. Burch).

When you see that there has been a clear increase in global temperature that correlates with a significant increase in CO2 emissions, it's pretty clear as to what the cause is.