The wildfire climate feedback, tundra´s case: megatonnes of extra CO2

Tundra wildfires pose climate feedbackGlobally 2007 was one of the hottest years on record. In the Arctic it led to the thus far smallest sea ice extent.

But that’s not the only thing unprecedented that happened in the far north. For the first time in 10,000 years fire raged on a massive scale, burning 50 years of accumulated carbon and leaving a soot-blackened soil as prey for albedo feedbacks, further damaging the permafrost.

Forest fire feedback

On Tuesday we addressed the forest fire climate feedback, illustrated by a new study [and PNAS publication] of the Yellowstone Ecosystem, but with implications for the wider taiga biome. Climate change can also promote wildfires in tropical forests, as a new form of droughts disturb the rainy cycle in for instance the Amazon.

Endless stretches of thawing peat

And warming can also stretch the northern boundary of the phenomenon, to areas that have thus far been too cold – too frozen actually – to catch fire: the tundra biome, stretching from Alaska and the north of Canada, to the polar regions of Scandinavia, Russia and Siberia.

Even though by definition the tundra is not real forest, there is still an enormous amount of biomass to burn, not just in the living vegetation, but also -especially- in the thick peat formations that it formed, over many thousands of years.

2007 Anaktuvuk wildfire

At the height of the 2007 hot summer on the Alaskan North Slope the Anaktuvuk River Fire broke out, burning a thousand square kilometers of wilderness and releasing 2.1 megatonnes of carbon, some 7.8 megatonnes of CO2.

Such fires are not natural to the Arctic ecosystem. Ecologists of the University of Florida and University of Alaska Fairbanks that studied the event say it may never have happened before anywhere in our Holocene [that’s 10,000 years – at least, because the 100,000 years before that were all glaciated]. Yesterday their findings were published in Nature.

50 years of carbon

From this we learn the one Alaskan tundra fire of 2007 doubled the entire cumulative burned area of Arctic tundra since 1950. The carbon release of the wildfire* was ‘two orders of magnitude larger’ than natural carbon exchange, emissions and sequestration from natural biomass oxidation and growth.

Carbon dating showed the fire reached considerable depth, burning a 50 year old layer of peat. That means the tundra vegetation now needs decades of undisturbed growth to compensate the carbon damage – decades in which the 2007 temperature extreme can become the new norm.

Arctic fire fighters

If we don’t succeed in mitigating the cause of the problem, we should at least consider investing in tundra fire prevention and suppression, one of the authors suggests – a costly business, that many miles from civilisation.

[*) The authors state that the positive climate feedback posed by an increase in tundra wildfires could also be more important – expressed in tonnes of carbon – than the negative feedback of ‘Arctic greening’ – essentially the taiga biome creeping towards the pole under influence of warming, gradually pushing the genuine tundra in the Arctic Ocean.]

© Rolf Schuttenhelm |

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