Drought is a better predictor of Amazonian fire frequency and severity than the extent of forest cover or other vegetation present, according to a new study down in the Ucayali region of Peru.
It challenges the longstanding notion that direct human activity, such as forest disturbance or agricultural practices, is the greatest single driver of fires in the Amazon.
Drawing on ten years of remote sensing data and over 700 interviews with local farmers, the authors suggest that fire size and intensity is at least as important as the number of fires in determining their ecological impact—perhaps even more so.
The findings have serious implications for fire management, adaptation, and damage mitigation.
They are also very timely.
DRY PERIOD, FIRE PERIOD
“If you look at the global climate data, there is a high probability of long periods of dryness in the future,” says Miguel Pinedo-Vasquez, Senior Scientist at the Centre for International Forestry Research (CIFOR) and one of the study’s authors.
“The catastrophe is already happening. It happened in 2005 and 2010, with the mega-fires in the Amazon and it’s happening in the Western Amazon as well. Uncontrolled fire is going to be the main hazard in the region.”
While those hazards certainly include loss of life and property, it doesn’t end there.
Now, with a really high level of accuracy, we can predict how severe the fire season is going to be
Increased fires in the Amazon pose a threat to the ecosystem itself. Unlike temperate species, tropical forest trees did not evolve in the presence of intense natural fires, and are less able to survive them.
A 2014 study in southeast Amazonia notes increases in tree mortality of 226% to 462% during periods of severe drought, much of which was associated with unusual fire activity. Large fires and the associated collapse of the forest canopy can also leave burned areas open to invasion by more flammable grasses, creating a cycle of negative feedback.
But Amazonian fires also have implications for the global climate. Under normal (or formerly normal) conditions, the Amazon absorbs more C02 through biomass growth than it emits through burning and decomposition: roughly 2 billion tonnes more per year.
During the mega-fire year of 2005, however, it produced a net 5.2 billion tonnes—just under the 5.4 billion emitted annually by the United States. During the even larger fires of 2010, the net emissions rose to an unprecedented 8 billion tonnes. Both 2005 and 2010 were years of exceptional drought.
If there is good news in the new research, it is that the increased understanding of the drivers of fire creates an opportunity for better management practices.
FORECASTING THE DRY
Predicting drought is now more accurate than ever before.
Contrary to popular opinion, El Niño or La Niña phenomena do not cause the droughts—at least not in Western Amazonia.
“Our own research confirms that there is no connection,” says Pinedo-Vasquez. “But there is a strong correlation with changes in the surface sea temperatures in the Atlantic. Now, with a really high level of accuracy, we can predict how severe the fire season is going to be.”
Such predictive capacity, along with the insights into the aggravating factors in fire intensity, pave the way for more informed and better executed control measures.
Among the most highly recommended of these are nationally or regionally coordinated fire calendars: essentially, efforts to concentrate the fires set by local people in times of higher humidity, when the danger of escaped fires is greatly reduced.
“Fires that might require the efforts of 15 or 20 people in extremely dry conditions can be contained by three or four during seasons of frequent rain,” says Pinedo-Vasquez.
Here the Ucayali study provides another vital clarification. Across the ten years of the study, overall fire damage in the region was not a product of the number of fires alone.
INTENSITY AND IMPACT
Even though humans started nearly all fires, the size and intensity of fires in a given year was more indicative of their overall impact on the ecosystem than the number of ignition points.
Catastrophes are happening, but we understand them now
Numerous fires, if adequately scheduled and contained, may actually cause far less damage than a smaller number of intense, out-of-control fires—and yet blanket fire suppression and criminalization efforts are still widely practiced across the region.
For Pinedo-Vasquez, the key is attention to the social context. He points out that fire has been a land management tool in the Amazon for millennia.
“Catastrophes are happening, but we understand them now. People use fire because they have to make a living. It’s an economic issue,” he says.
“We have to engage with them in a process of fire adaptation, and that process has to be done on the basis of on-the-ground information, good decision making and an understanding of the value of fire to the livelihoods of the people—not by punishing them.
“Punishment is not helpful.”
For more information about this research, please contact Miguel Pinedo-Vasquez – firstname.lastname@example.org
This research was supported by National Science Foundation and by the Center for International Forestry Research (CIFOR).
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