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Canada’s Rapidly ‘Greening’ North is Bad News For Everyone

A new study shows the Arctic is turning green.

by Elizabeth Howell
Jun 3 2016, 4:00am

Credit: NASA's Goddard Space Flight Center/Cindy Starr

Going green sounds like a good thing, but not in Canada's north. There, a changing climate and warmer temperatures are transforming semi-frozen tundra into grass for much of the year.

Almost 30 percent of the land area of Canada and Alaska together is greener than it was in 1984, a new study in Remote Sensing of Environment reports. While that's not a surprising statistic to these researchers—it echoes what other studies have been showing—the new study documents in painful detail just how these changes are happening.

Previous satellite studies showed a resolution of roughly 4 kilometers squared. The latest data using Landsat 5 and 7 (the same satellite series that showed us the shocking Fort Mac fires) brings that resolution down to just 30 meters, meaning they could do a hyper-local analysis. As Landsat's infrared sensors are sensitive to the greens of leaves and bushes, this allows researchers to map how tree cover or land cover change over time.

The view from a plane that is carrying instruments to measure the health of vegetation in the Arctic tundra of the Northwest Territories of Canada. Credit: NASA/Peter Griffith.

More importantly, the fine resolution shows changes happening on individual hills, and allows for comparison between areas. This so-called "local" effect on greening has not been well-studied, lead author Jeffrey Masek, the chief of the biospheric sciences laboratory at the NASA Goddard Space Flight Center, told Motherboard. In general, however, scientists know that the Arctic is changing more rapidly because of climate change than other parts of the world.

"The canary in the coal mine is these high latitudes," he told me, "so we want to see to see how these areas are responding."

"Greening" is a catchall term for many different processes, including tundras becoming shrubland, or pre-existing shrubs getting bigger and denser. Melting ice in parts of the north accelerates global warming because the sunlight can't reflect off grass as effectively as it can off blinding white ice, so it contributes to warming even further. In this way, greening accelerates warming—but not as fast as melting ice.

Somewhat surprisingly, more greening was also seen on Canada's southern border with the US, in the heart of its agricultural lands. This is probably due to a longer growing season, but the exact reason needs more study, Masek said.

The study also examined "browning", a process that's impacting forested areas of Canada, which are becoming less healthy over time. Trees look browner from space because of more frequent forest fires (which is linked to climate change).

A greener Canada sounds lovely, maybe even like a good thing. But obviously, when we're talking about the Arctic, it's just another worrying sign of climate change.

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