Climatide

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Could woolly mammoths slow permafrost melting?

Imagine a global experiment whose effects last hundreds to thousands of years, and in which each and every living being – indeed, even the oceans, continents, and atmosphere – are all subjects. Sounds kinda scary, right?

The scary part, according to Dr. Max Holmes – a senior scientist at Woods Hole Research Center – is that we’re already doing that. It’s called climate change.

Holmes has spent years studying Arctic rivers, particularly how they’re changing due to both natural and human processes. With a boyish grin, he describes the excitement that he and his team feel each year when they return to find dramatic visible differences in their field sites – shorelines crumbling and eroding as permafrost melts. After all, they’re scientists who study change; seeing it happen before their very eyes is incredible! Then the father in him kicks in, and his face falls as he relives the moments (it happens again and again, he says) when he is forced to realize that the changes he’s watching aren’t part of some laboratory experiment. They are harbingers of changes happening across the globe as a result of rising greenhouse gas levels, and they are a reminder that things could get a lot worse than expected, a lot sooner than expected.

That’s because the Arctic’s frozen ground holds vast quantities of ancient carbon – twice what’s currently in the atmosphere. As global warming melts the permafrost, that carbon is released into the atmosphere in the form of methane – a greenhouse gas 23 times more powerful than carbon dioxide. That methane accelerates warming even more, leading to more melting, which leads to … you get the idea. It’s what scientists call a positive feedback loop. Melting permafrost is thought to be behind some of the most rapid and dramatic periods of warming in Earth’s past, and it has many scientists – like Holmes – very worried about the future.

That concern led Holmes to search for seriously outside-the-box ideas about how to slow global warming. And a budding relationship with Sergey Zimov, a Russian researcher that Holmes describes as passionate, if a bit eccentric, presented him with just such an idea. Holmes described the idea in what, to my mind, was the star talk of the recent 2011 TEDx Woods Hole event.

Zimov oversees an area in Siberia known as Pleistocene Park. For several years, Zimov has been reintroducing large grazers – wild horses, reindeer, buffalo – in hopes of turning the sparse forests that now cover the area back into the lush grasslands that defined the region during the last ice age, when woolly mammoths still roamed the Earth. Zimov is apparently even hoping to eventually reintroduce woolly mammoths, themselves (or at least a mammoth-elephant hybrid) … assuming Japanese scientists can pull off the genetic stunt of fertilizing an elephant egg with sperm from a frozen mammoth and having an elephant carry that egg to term (there are a lot of very bit IFs in there).

Zimov’s motivation for Pleistocene Park is to settle a long-standing debate about wiped out woolly mammoths and other extremely large animals of that time. One theory is that climate change – the warming that followed the last Ice Age – resulted in a shift from grasslands to forests, starving the large herbivores. But Zimov (and others, to be sure) thinks it was the other way around – that human hunters wiped out woolly mammoths, and that allowed grasslands to turn to forests. He hopes to prove the point by demonstrating that large grazers and the grasslands they both depend on and maintain can do just fine in a warmer world if they’re left alone.

Holmes says he doesn’t have a stake in the woolly mammoth whodunnit question. But he saw an opportunity to use Pleistocene Park to test a different theory – that grasslands can keep the ground colder and, thus, slow the melting of the permafrost and the accelerating warming cycle that kicks off.

The idea is that for nine months of the year, Arctic grasslands are essentially flat, white (i.e. snow-covered) surfaces that reflect a lot of sunlight back into the atmosphere before it has a chance to warm the ground. In contrast, forests of deciduous conifers (evergreens without the ‘ever’ part) are dark sunlight absorbers that can transmit heat to the ground. Keep in  mind that the Arctic spends months every year in complete darkness, so changes in how much light would be reflected is a moot point. But Holmes says the differences in vegetation could have a major impact during spring and fall.

Add to that the fact that large grazers pack down the snow, reducing it’s insulation value. That’s important, because grass and snow can actually keep ground temperatures as much as 30ºC warmer than the air, which gets down to a truly frigid -40ºC (the magic number that just happens to also be -40ºF). Holmes has done experiments using snow fences to allow snow to build up on one side, but not the other, then shovelled it off in spring and compared the state of the permafrost. Not surprisingly, there’s more melting under the deep snow.

Holmes’ work in Pleistocene Park is in its early stages, and could take years to show results. Even then, he concedes that reintroducing large grazers – even to all of Siberia – wouldn’t solve the climate change problem. But Holmes says it might, just maybe, slow down permafrost melting enough to give us time to figure out the rest of the solution.