“Government decision makers, international aid groups, and the media are often quick to blame flooding on deforestation caused by small farmers and loggers,” said Patrick Durst, the senior forestry officer for the UN Food and Agriculture (FAO) Regional Office for Asia and the Pacific.

“The conclusion is not only wrong, scientifically, but such misguided views have in the past prompted governments to make life harder for poor farmers by driving them off their lands and away from the forests, while doing nothing to prevent future flooding,” he added of the report, Forests and Floods: Drowning in Fiction or Thriving on Facts?

The report said the sharp increase in economic and human losses attributed to floods is caused not by deforestation but mainly by the simple fact that more people are living and working in flood plains. As a result, many floods that previously would have been only minor events now become major disasters.

Drafted by FAO and the Centre for International Forestry Research, the report acknowledges that forests can play a role in minimizing runoff but it concludes that there is no evidence that a loss of trees significantly contributes to severe widespread flooding. Even at the local level flood-reducing effects of forests are heavily dependent on soil depth and structure, and saturation levels, not exclusively on the presence of the trees, it notes.

“Planting trees and protecting forests can have many environmental benefits, but preventing large scale floods is not one of them,” Centre Director-General David Kaimowitz said. “If deforestation was causing floods, you would expect a rise in major flood events paralleling the rise in deforestation, but that is not the case. The frequency of major flooding events has remained the same over the last 120 years going back to the days when lush forests were abundant.”

The report said it was time for national and international policy makers and development agencies to acknowledge that objective scientific research does not provide easy answers when it comes to understanding flooding. Instead, a complex interplay of natural and man-made conditions produces major floods and exacerbates their impact. For example, large floods always have been a natural, and beneficial, part of the ecosystem. But a range of human activities, such as draining and developing wetlands and damming and altering stream flows, can make them worse.