Drying intensifying wildfires, carbon release ninefold, study finds

Drying intensifying wildfires, carbon release ninefold, study finds
The 2003 Erickson Creek Fire burned more than a month and affected about 48,000 hectares of boreal forest. Credit: Merritt Turetsky

Drying of northern wetlands has led to much more severe peatland wildfires and nine times as much carbon released into the atmosphere, according to new research led by a University of Guelph professor.

The study, published today in Nature Communications, is the first to investigate the effect of drainage on accumulation in northern peatlands and the vulnerability of that carbon to burning.

"Russia, Indonesia and Canada all have abundant peatlands, but they also have been hotspots for intense peat fires in the past decade," said Guelph professor Merritt Turetsky, who worked on the study with William Donahue of the Water Matters Society of Alberta and Brian Benscoter from Florida Atlantic University.

In pristine states, peatlands often resist fire because of their . "Our study shows that when disturbance lowers the water table, that resistance disappears and peat becomes very flammable and vulnerable to deep burning," she said.

Recently, destructive peat fires plagued the Moscow region. In the late 1990s, severe Indonesian fires in drained peatlands released carbon equivalent to 40 per cent of annual global .

"Our results demonstrate the importance of cumulative impacts," Turetsky said.

Peatlands store vast amounts of carbon by pulling out of the atmosphere. For millennia, they've accumulated plant debris — the remains of wood, moss, and other plants — and locked it up in layers of saturated peat more than five metres deep in places.

Drying intensifying wildfires, carbon release ninefold, study finds
This is a photo of a boreal wildfire. Credit: Natural Resources Canada, Canadian Forest Service

Northern peat covers large swaths of the landscape. Because about half of that peat consists of carbon, it is a globally important carbon pool.

But peatlands are also carbon sources, as this same debris fuels . "While fire is a widely recognized disturbance in upland forests, the impacts of fire on peatlands and their carbon storage have been largely overlooked," said Benscoter.

The majority of the world's peatlands are located in northern regions, and Canada is home to some of the largest on the planet.

"The extensive deposits of peat in Canada are an important natural resource, but one that is being disturbed more often, not only by wildfire but also by human activities," Turetsky said. Previous studies have documented the effects of land use practices and global warming on the ecology of peatlands. "But we wanted to examine how decades of lowered water table in peatlands might affect wildfire behaviour, and that required a very large experiment."

To determine those effects, the researchers used a unique outdoor laboratory. A large section of a boreal fen near Slave Lake, Alta., had been drained over 20 years ago in a wetland drainage project. A portion of the fen including drained and pristine plots burned in a wildfire in 2001 allowed for a natural experiment.

Earlier research had documented increases in tree growth and carbon storage after drainage. "But nobody had looked at the impacts of dewatering on fire intensity and associated carbon gains or losses," Donohue said.

The results were surprising, he said. Long-term drainage actually increased tree productivity and in the fen soils. But the lower also changed wildfire conditions, and losses of soil carbon to burning in the drained areas increased ninefold.

"Even though the organic matter accumulation doubled over two decades after drainage, severe burning triggered the complete loss of this newly stored carbon, plus a further 450 years' worth of peat accumulation," Donahue said.

"Currently, peatlands are considered important global stores for carbon. But we've shown that human disturbance or climate-induced drying can switch peatlands from sinks to potentially huge sources of carbon, with losses associated with severe burning far outweighing long-term rates of sequestration."

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Nov 01, 2011
Drying intensifies wildfires, but doesn't putting out wildfires also ruin the natural process of burning that should have occurred?

Think of the atmospheric aerosols that get sequestered by putting out forrest fires. Human intervention has lead to a decrease in atmospheric particles that could potentially block out more sunlight and this ultimately effects the radiative balance of our planet. Imagine how many acres of naturally burning vegatation have humans put out and the change in temporary atmospheric composition this has created...

Nov 01, 2011
Drying intensifies wildfires, but doesn't putting out wildfires also ruin the natural process of burning that should have occurred?

It turns out that most fires in the world are started by people and can and does change some areas flora and fauna. By the same token the areas we do affect by putting out natural fires is far smaller than the areas we affect by lighting fires.

Nov 01, 2011
Drying intensifies wildfires, but doesn't putting out wildfires also ruin the natural process of burning that should have occurred?

There is a big difference between the aerosols and CO2. Linger time. Aerosols will eventually settle to earth as soot. CO2 stays in the atmosphere for 10000 of years. That is what is so dangerous when we hit the tipping point. It will be with us for a long time and so will the effects.

Nov 02, 2011
Think of the atmospheric aerosols that get sequestered by putting out forrest fires.
Forests put out their own aerosols, even when there are no fires. Things like plant pollen and fungal spores, for instance.

Also, fire suppression only delays the fire, and when the fire does burn it burns hotter and consumes larger areas of the forests due to more fuel having accumulated, and the forest being denser than normal. Prior to fire suppression practices, firestorms would have been a very rare event. Nowadays, firestorms are a regular threat, and when they do develop they create strong convective systems that catapult the combustion products into the stratosphere.

The old methods of fire suppression are now widely understood as being in error. Modern forestry doctrine involves periodic setting of controlled fires.

Nov 02, 2011
CO2 stays in the atmosphere for 10000 of years.
No it does not. Within about 200 years or so it equilibrates with the oceans, leaving something like only 30% of the originally added amount in the atmosphere. This then slowly gets sequestered into carbonates and buried bio-matter over the next 1000-2000 years -- until atmospheric concentrations once again reach an equilibrium between sequestration vs. emission (mostly volcanic) rates.

Still, the point is valid that CO2 has by far longer atmospheric lifetime than soot, sulphates, or any other aerosols.

Also, the danger exists that as the oceans warm up, they will be capable of absorbing less and less additional CO2, potentially even themselves becoming a CO2 source (same phenomenon as cold vs. warm fizzy drinks.) However, it takes a very long time for the oceans to heat up (think centuries), and they may never heat up to a point where they begin to actually out-gas CO2.

Nov 02, 2011
@Pink, I read somewhere that the linger time for CO2 in the chemical mix that's our atmosphere was in the 10K Year range. It's possible I'm wrong on the time scale, I don't have the reference in front of me. Are you sure it's in the 1000's?

Regardless, the corals an top levels of the oceans are already being acidified with CO2. The death of the corals is the first indicators of what is going to happen to us.

Nov 02, 2011
I'm pretty sure that it's 1000 years or so. Let me see if I can Google something up.... Here:


And here:


Yes, there's an asymptotic decline can take as much as 10,000 years, but overwhelmingly most of the sequestration occurs in the first 1-2,000.
the corals an top levels of the oceans are already being acidified with CO2. The death of the corals...
The corals aren't dying because of acidification (yet). So far, the bleaching events have been variously linked to increased water temperatures, invasive/uncontrolled predator species, and eutrophication (those are the studies I've seen.)

The acidification of the oceans is a looming threat (that will materialize in full force if we continue with business-as-usual); so far it is down barely 0.1 on the pH scale relative to pre-industrial levels:


Nov 03, 2011
You are right. I couldn't find the article in support of the 10000 year linger time. It was here in Physorg about year ago but its difficult to track down. Anyway I think the point it made was, as global warming increased Ocean temperatures, CO2 uptake into the oceans would decrease to the point of not being a sink at all. In fact it would start to leak CO2 back into the atmosphere. Thus the CO2 levels would feed back resulting in the 10,000 year figure.

Thanks for the references Pink. Interesting reading. I wish I could find the original link for you, it a deep dive into "tipping point" and "feedback" articles.

You know http://www.ess.uc...ig1.html is a really good graphic. I've not seen that before. It's excellent.

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