Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


As Amazon urbanizes, rural fires burn unchecked

Fewer farmers plus more roads and drought bring increased risk

Over past decades, many areas of the forested Amazon basin have become a patchwork of farms, pastures and second-growth forest as people have moved in and cleared land--but now many are moving out, in search of economic opportunities in newly booming Amazonian cities.

The resulting depopulation of rural areas, along with spreading road networks and increased drought are causing more and bigger fires to ravage vast stretches, say researchers in a new study. The study, focusing on the Peruvian Amazon, is the latest to suggest that land-use changes and other factors, including possibly climate change, are driving increasingly destructive wildfires in many parts of the earth. An interdisciplinary team at Columbia University's Earth Institute will publish the paper this week in the Proceedings of the National Academy of Sciences.

Nearly all fires in the Peruvian Amazon are set by humans seeking to burn woody vegetation off pastures, clear fallow land for planting, and release nutrients back into the soil—millennia-old methods used in many parts of the world. So-called slash-and-burn agriculture got a bad name in recent decades when fast-growing numbers of tropical ranchers and farmers deforested vast areas with fire, leading to massive soil erosion and releases of carbon. With many now abandoning land or working it only part time in favor of city jobs, some scientists started thinking this might lead to fewer fires. But the study shows the opposite: with fewer people around to control fires, and flammable small trees and grasses quickly taking over uncultivated plots, more blazes are spreading out of control and burning off bigger areas--not only forests but farms, fruit plantations, homes and villages.

"Farmers are often blamed for deforestation and environmental destruction, but they are fairly sophisticated in managing fire—they plan when, how and where to burn the land," said lead author María Uriarte, a forest ecologist in Columbia's Department of Ecology, Evolution and Environmental Biology. "However, when you have more fallow land and fewer people around to work at control, that combination generates these big fires."

Between 1993 and 2007 (the year of the latest census), the population of the Peruvian Amazon went up over 20 percent, to some 7.5 million. But urban areas grew much faster; so many people moved from the countryside to the cities, rural populations of some provinces saw declines of up to 60 percent. This is true around the frontier city of Pucallpa—now Peru's fourth-largest municipality, and a trading hub for the western Amazon. Much of the Brazilian Amazon is undergoing a similar transformation. Rural populations in almost all nine nations comprising the Amazon basin, which also include Venezuela, Colombia and Bolivia, are projected also to decline, even if cities grow.

Ever denser spiderwebs of roads are spreading from these cities, making previously inaccessible places reachable for logging, farming and other activities. On top of this, the Amazon suffered massive droughts in 2005 and 2010—events previously thought to take place only once every 100 years. In lands already made more flammable by logging of humid old-growth rainforests, this led in 2005 to fires that burned some 800,000 acres, by conservative estimates, in the Brazilian state of Acre and around Pucallpa alone. A 2011 study by members of the Columbia team indicates that the droughts are connected to fluctuations in temperature over the faraway Atlantic Ocean; some models project they will get worse as global climate warms.

To assess the prevalence and causes of uncontrolled blazes, the researchers combined region-wide climate data, remote-sensing images of land use and fires, and field interviews with farmers around Pucallpa—often conducted amid fires that were still burning. (See slideshow and videos of the team's fieldwork) Not surprisingly, they found that dry conditions and proximity to roads correlated with increased fires. But fires increased most powerfully both in frequency and size where rural population declines were the steepest—an indication that a certain level of human presence, with neighbors watching out for each other, helped damp down destructive outbreaks, while fires took over human-altered landscapes once the people thinned out.

"Projected declines in rural population across Amazon countries and expansion of road infrastructure combined with more frequent droughts predicted by some global climate models presage greater damage from fires in the future," the authors say. However, they see hope in some recent developments. These include their own work showing that big droughts can be predicted using observations of sea-surface temperatures, which could lead to early warnings of dry seasons to come. Also, many Amazonian lands are now being taken up with big plantations of oil palms, which are not so susceptible to fire. Unfortunately, a separate study by team members last year showed that the plantations are most often being carved out of still-intact forest—not the more flammable former small farms—but team members say government policies encouraging conversion of small farms to oil palm could help.

The other authors of the study are Miguel Pinedo-Vaquez, Ruth DeFries and Victor Gutierrez-Velez, also of Columbia's Department of Ecology, Evolution and Environmental Biology; Katia Fernandes and Walter Baethgen, from Columbia's International Research Institute for Climate and Society; and Christine Padoch, of the New York Botanical Garden. Padoch and Pinedo-Vaquez are also associated with the Center for International Forestry Research.

Fires in Western Amazonia project website:
Slideshow and videos on the team's research in the Peruvian Amazon:

Maria Uriarte discusses her research in Puerto Rico:

The paper, "Depopulation of rural landscapes exacerbates fire activity in the western Amazon," is available from the authors or the PNAS News Office: 202-334-1310 or

Scientist contacts:
Maria Uriarte 212-854-1494
Ruth DeFries 212 851 1647
More information: Kevin Krajick, Senior Science Writer, The Earth Institute 212-854-9729
The Earth Institute, Columbia University mobilizes the sciences, education and public policy to achieve a sustainable earth.

The Center for Environmental Research and Conservation (CERC) is Columbia University's voice of the living world and the Earth Institute's principal center for the study of biodiversity and its role in sustainable development.

Kevin Krajick | EurekAlert!
Further information:

More articles from Ecology, The Environment and Conservation:

nachricht Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide

nachricht Malaysia's unique freshwater mussels in danger
27.09.2016 | The University of Nottingham Malaysia Campus

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Ice shelf vibrations cause unusual waves in Antarctic atmosphere

25.10.2016 | Earth Sciences

Fluorescent holography: Upending the world of biological imaging

25.10.2016 | Power and Electrical Engineering

Etching Microstructures with Lasers

25.10.2016 | Process Engineering

More VideoLinks >>>