In today’s Academic Minute, Dr. Maria Uriarte of Columbia University’s Earth Institute examines the use of fire as an agricultural tool in South America.
Maria Uriarte is a forest ecologist in the Department of Ecology, Evolution and Environmental Biology at Columbia University. Her lab examines forest ecological dynamics in response to natural disturbances and human land use. Her current projects include an examination of the use of fire as an agricultural tool in the Amazon basin. She holds a Ph.D. from Cornell University.
Dr. Maria Uriarte – Assessing Slash and Burn Agriculture
For thousands of years, farmers have used fire for clearing forest and fallow fields, recycling nutrients, and reducing pests. In many tropical regions, farmers rely on slash and burn--a cheap, labour-saving way of managing land. Now, with increasing awareness of climate change, the use of fire in agriculture has gotten a bad reputation. It has been associated with deforestation and increased greenhouse gas emissions. But, is this true?
To assess the prevalence and causes of uncontrolled blazes in the Peruvian Amazon during the past decade, my colleagues and I combined climate data, remote-sensing images of land use and fires, and field interviews with farmers. We also looked at demographics. Throughout the tropics, many farmers are abandoning land or working it only part time in favour of moving to cities for jobs and services. The population of the Peruvian Amazon is going up--but urban areas are growing much faster than the countryside, and in many places, rural populations are declining, as people move to cities.
Going in, we thought that lower rural populations might lead to fewer fires. Instead, we found that the number and size of fires increased most strongly where rural population declines were the steepest. This told us that a certain level of human presence, with neighbors working together to control fires, helps damp down destructive outbreaks. Although farmers are often blamed for environmental destruction, they plan when, how and where to burn the land in ways that minimize risk. But once people alter a landscape and then move away, fuel loads increase and fires can take over. Not surprisingly, we found that dry conditions and proximity to roads also led to more fires.
ural populations are projected to keep declining in most of the Amazon while roads expand. And, climate change may bring more frequent drought, so fire risk is likely to increase. We may be able to take steps to minimize the danger. But we need to recognize that we can’t blame everything on farmers—and that the rapid urbanization of our species can have unforeseen consequences.