As more Peruvians  move to the cities, fires will burn in the outskirts, warn researchers. Danielle Pereira/flickr.

BOGOR, Indonesia (8 February, 2013)_Wild fires in the western Amazon are being exacerbated by a population shift: As farmers move from rural areas to cities, they leave behind uncultivated landscapes that are drier and more susceptible to runaway blazes, a new case study indicates.

And, when fires do break out, there are fewer bodies around to control them.

Maria Uriarte and other researchers looked at wild fire frequency in the Peruvian Amazon from 2000 to 2010.

While acknowledging previously known causes such as drought, timber extraction and road infrastructure expansion, they found that at least one other contributing factor is in play.

“Fewer people leads to more fires,” said Uriarte, lead author of the province-scale analysis that appeared in the Proceedings of the National Academy of Sciences of the United States of America.

There have been a large number of fires in the Amazonia (and globally) over the past decade, leading to forest degradation, carbon emissions, worsening air quality and property damage.

In Peru, the government estimates that more than 22,000 hectares burned in the Ucayali region in 2005, a significant amount but, according to the study, likely a gross underestimate. Of the officially recognised burned areas, about 16,000 hectares were in forests, more than 5,000 in pasture, and the rest in fruit plantations, manioc fields and the villages and homes of farming families.

Controlled fires have been used for millenia in Amazonia and elsewhere to clear and manage plots of land for cultivation and other economic purposes. Though farmers traditionally have been careful to make sure the  blazes did harm their own assets or those of others, rapid economic and social shifts have changed all that.

Up until now, most public policies aimed at eliminating the use of fires have largely been unsuccessful, said Christine Padoch of the Center for International Forestry Research and a contributor to the study, stressing the importance of implementing policies that instead find ways to help people regulate and adapt their fire use.

The authors said that because it’s cheap and requires little labor, the use of fire for land management is likely to increase in Peru as members of rural communities head to the city in search of better services such as healthcare and education. (Of the 81 provinces surveyed, all but five recorded urban population growth).

The burn scars in the depopulated areas are getting larger and in areas with a high percentage of fallow land, the risk of more fires increases, said CIFOR’s Miguel Pinedo-Vasquez, another of the authors.

“At the same time, there are fewer people and, probably, less communication and cooperation among neighbors,” he said, “making it harder to keep fires under control.”

In the past, the wetter conditions and less marked seasonality that generally prevail in the Amazon have been presumed to limit the amount of wild fires. But extensive clearing of humid forests for agriculture and pasture, especially along the eastern slope of the Andes, compounded by the migration to the city, have made the region more vulnerable to blazes, the authors wrote.

The research group set out to determine if droughts in the Amazon in recent years are partly linked to global warming. They looked at climate, geospatial and province-level census data, but also surveyed farmers.

Their aim was to look at linked biophysical and socioeconomic factors associated with fires and how they interact with climate variability, something that is still poorly understood.

“If you are a farmer and have invested a certain amount of money on your land, and an accidental fire occurs, you lose your investment,” said Uriarte.

“So say a farmer experiences two fires in five years, there is less of an incentive to keep working on the land. However, understanding the way farmers respond to this change in the landscape is hard to grasp because human behaviour is very complex.”

Much more research is needed, Uriarte said.

But for the immediate future, she emphasised the importance of strong fire coordination.

“Peru doesn’t have explicit fire policies. There must be enough action from government, farmers, communities to control them.”

Farmers could begin by planting things that are less susceptible to fire, Uriarte suggests.

“There are development incentives to plant oil palm, for example, because you don’t have to keep burning it like you might with a different crop – that carries a different set of issues, but there may be solutions that combine land uses that require less fire.

“There will have to be a very careful approach, and consideration of existing institutions and structures to make this happen.”

At the same time, improving services in rural areas may provide more incentive for farmers and their families to stay put.

“That also would help with fire control.”

This study forms part of the CGIAR research program on Forests, Trees and Agroforestry and was supported the National Science Foundation (award number 0909475) and the Tinker Foundation.