A huge smoke cloud rises into the air in Tuolumne County on Tuesday, 20 August 2013, as the Rim fire continues to rage. This image was shot coming down from the Glacier View. Photo: Barbara Davidson / Los Angeles Times

4 September 2013

SAN FRANCISCO (The New York Times) – The huge wildfire scorching one of America’s most beloved national parks, Yosemite, has rained ash on San Francisco’s water supply and jolted the nation.

Experts say this is just a foretaste of major fires to come, in the United States and much of the world.

Increasing incursions by humans into forests, coupled with altered forest ecology and climate change, will make fires bigger and more destructive, with implications for air quality as well as homes and infrastructure.

“We face the increased risk of fires almost everywhere,” said Chris Field, director of the department of global ecology at the Carnegie Institution for Science, who is co-chairman of a working group for the Intergovernmental Panel on Climate Change.

There have always been forest fires, of course. But their patterns are changing because of people.

Humans are often responsible for starting the fires, accidentally or intentionally; some spin out of control. The suppression of smaller fires can lead to buildups of burnable brush that can feed a huge, destructive blaze when it is sparked. That is true of the California blaze and many others in the American West; it is also what has happened in significant recent blazes in Turkey, according to Chadwick Oliver, director of the Global Institute of Sustainable Forestry at Yale University.

“We don’t need much of a spark to set off a fire that spreads long distances through the crowded, continuous forests,” Dr. Oliver said.

And climate change, to which humans contribute, is heating up and drying out some — though not all — areas.

Global studies of wildfire patterns are rare. But a paper published last year in the journal Ecosphere predicted that climate change would have an effect on wildfires that varies widely, especially in accordance with a given region’s precipitation patterns.

The paper — which focused on climate change but not other variables, like changing land management — projected that dry parts of the middle latitudes and Australia are likely to see more fires over the long term. The American West, already a tinderbox, will become more fire-prone. So, too, will high-latitude areas, the study found, partly because the carbon-rich peat soil there will burn under extreme weather conditions.

The pattern of increased wildfires by the end of this century appears “clear for temperate and northern regions of the world, and it is most striking for the boreal forests/taiga and tundra biomes,” the paper stated.

Parts of the tropics may become less fire-prone with climate change, the study said. That is because global climate models largely agree that areas near the Equator will see more precipitation with climate change, according to Max Moritz, one of the Ecosphere study’s researchers, who heads a laboratory focused on fires at the University of California, Berkeley.

“This would — all other things being equal — tend to dampen prospects for fire in the equatorial rain forests,” Dr. Moritz said, adding that further research on seasonal precipitation patterns was needed.

Significant risks remain for the tropics, Dr. Field of the Carnegie Institution for Science noted. People sometimes set fires to clear land — and the loss of some parts of a tropical forest to fire or clear-cutting can create a feedback effect.

“One of the big concerns in Brazil, especially, is we know that the forests play a role in the amount that it rains,” Dr. Field said. Moisture in the Amazon is recycled — so if there is less forest to do the recycling, the rest becomes drier and more vulnerable, he said. [more]

Wildfires and Climate Change



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