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Increased Arctic Shrubbery May Destroy Permafrost

Increased Arctic Shrubbery May Destroy Permafrost

It’s hard to be 100% certain of the exact consequences of climate change. The cascade effect, where changes in one system affect others, which affect more in turn, makes it very difficult to predict the future of Earth’s complexly inter-related systems without a lot of real-life data.

Case in point: last year, an article was published in Global Change Biology, a scientific journal, about the effects of increased shrubbery on the Arctic tundra. The tundra is a desert-like ecosystem in the far North. Below a certain depth, the ground is frozen and never, even during the brief summers, thaws. This is the permafrost. In the thin layer of ground that lies above the permafrost layer, tough grasses grow and not much else.

At least that’s how it was 20 years ago, when I took elementary school geography. But the Arctic is changing more rapidly due to climate change than most parts of the world. There’s been a significant increase in the amount of shrubbery in the tundra, and what this will mean ecologically and geographically is not yet clear.

The writers of this original paper (which I’m afraid I can’t find online) did some controlled field studies, measuring temperatures of exposed ground versus shaded ground under shrubbery. They determined that the shrubbery might actually help to keep the ground, more particularly the permafrost, cool, by shading it from the sun. Thus the shrubbery that has been springing up in the wake of warmer Arctic temperatures may actually protect the permafrost from melting, at least for a little while.

But a new paper released in the latest volume of Environmental Review Letters blows that prediction out of the water. What the last study failed to take into account were the effects of albedo and transpiration from the new shrubbery. Albedo is just a measure of how good something is at reflecting away the sun’s rays and, therefore, heat. The almost pure-white Arctic tundra normally has a very high albedo. The highly reflective surface area is one reason the Inuit long ago invented slitted glasses to protect their eyes when out on the tundra on a bright day.

The sparse grasses don’t make much of a difference, but the darker, thicker shrubbery has an obvious effect, absorbing much more heat from the rays of the sun, and releasing this heat into the ground and air.

Additionally, transpiration, the absorption and release of moisture which is part of all plants’ metabolisms, is greatly increased with large, leafy shrubbery. A potential increase in humidity may also have an effect on the ability of the ground to cool itself through evaporation. The earlier paper didn’t take either of these effects, albedo or transpiration, into account.

All of which means that shrubbery, according to the more detailed and thorough study just published, may be another of those positive feedback loops, accelerating warming at the Arctic rather than slowing it. As a result, the melting of the permafrost may occur sooner than previously expected.

The tundra being a fairly precarious ecosystem to begin with, a major change like the melting of the permafrost might have any number of unforeseen effects. We’ll have to wait and see exactly what they are.

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The Convenience Button and the Ethics of Climate Change


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Photo credit: Dentren

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41 comments

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12:48PM PDT on Apr 14, 2012

Grazie per l'articolo.

2:08PM PST on Feb 7, 2012

Thanks for the article.

12:05PM PST on Feb 3, 2012

Interesting, thanks.

6:55PM PST on Feb 2, 2012

16 billion tons of CO2 that are not recycled and remain in the upper atmosphere for 100 years is from the burning of fossil fuels. The methane and CO2 released from oceans and melting ice is part of the accelerating effect of fossil fuel burning. If humanity has any hope of surviving it must stop mining and using the dirtiest fuel now.. and that would be coal plants worldwide (which make up at least 40% of the greenhouse gases) and Canada's downright criminal development of its tar sands, the dirtiest oil on earth.

6:49PM PST on Feb 2, 2012

Actually the worst consequences of melting the tundra which has been frozen for eons is the release of its trapped methane. Methane is a greenhouse gas many times worse than CO2. What is most dangerous is that the release of greenhouse gases from the oceans and ice sheets is accelerating not a constant..the earth has never experienced and is being overwhelmed by the release of these gases in such a short period of time..16 billion tons of excess CO2 a year..beyond what natural systems can recycle. Humanity is a complete disaster and a disease for all life on earth

6:11PM PST on Feb 2, 2012

Thanks for the information.

5:18PM PST on Feb 2, 2012

Thanks.

3:33PM PST on Feb 2, 2012

We should respect what god gave ti our home, his home.

2:45PM PST on Feb 2, 2012

Thanks.

10:22AM PST on Feb 2, 2012

"this original paper (which I’m afraid I can’t find online"
OK, so how about citing the date, journal issue number, and author? Odds are we could at least find a synopsis.

"It’s hard to be 100% certain of the exact consequences of climate change"
Actually, we can be 100% sure about the consequences that have already happened.

The tundra is not white- you're thinking of the glacial fields and icecaps. And, the albedo has declined steadily due to sooty fallout from our fossil fuel consumption. We could offset this by having white roofs and covering all our miles of blacktop with something lighter.

It's nice to see that Care2 finally has a science teacher on its roster, but I was hoping for more accurate reporting.

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