UN Report: Deforestation Does Not Cause Widespread Flooding

BOGOR, Indonesia, October 13, 2005 - The conventional view for 100 years has been that forests prevent floods by acting as a giant sponge, soaking up water during heavy rains. But a new report from a UN agency and a forest research group released today finds there is no scientific evidence linking large scale flooding to deforestation.

This holds true, according to the report, for recent flooding in China, Thailand and Vietnam as well as for the floods over the past week in Guatemala and El Salvador that claimed up to 2,000 lives.

The report, The report, "Forests and Floods: Drowning in Fiction or Thriving on Facts?" by the UN Food and Agriculture Organization (FAO) and the Center for International Forestry Research (CIFOR) says the floods blamed on deforestation almost always occur after prolonged rains, which saturate the soil, including forest soil, so that it can no longer absorb more water. Rain then has nowhere to go but into rivers where it fills them to overflowing.

Local loggers like these in Honduras are often blamed for landslides that follow severe storms. (Photo by I. Velez courtesy FAO)

"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."

There can be a political interest in leaving the conventional wisdom about forests and floods unchallenged, analysts with FAO and CIFOR who authored the report point out. Governments can respond to floods with logging bans and give the appearance to the public they are taking decisive steps to stop flooding.

The practical effect of such policies is to force poor farmers - who are routinely portrayed as major perpetrators of illegal logging - to abandon their lands, finds the report, a collaborative project that also involved the International Water Management Institute, the World Agroforestry Center and the International Center for Integrated Mountain Development.

For examples, the authors point to catastrophic floods in China, Thailand and the Philippines that prompted logging bans. Millions of people were thrown out of work, they say. In Romania, more than 1,000 people were recently prosecuted during a government crackdown after the country was devastated by flooding.

But others hold opposing views. In an article for the North by North East Tours newsletter, J.G. Learned writes of Laos, "In the monsoon season, horrendous mudslides bury entire villages in denuded areas. Most of those villages were contracted by logging companies to cut the surrounding forest – rather like paying a man to dig his own grave.

Mudslide on a denuded hillside in Laos. (Photo courtesy North by Northwest Tours)

International agencies may also have a stake in maintaining the forest-flood myth as it helps in "channeling aid funds to upland reforestation projects," the report states.

Concerning the Central American landslides that buried hundreds of people earlier this month, John Sauven, campaign director for Greenpeace UK, told the "Independent" newspaper October 5, "Unfortunately, something nearly always happens this time of year. Mudslides are becoming more and more common and deforestation certainly plays a role."

Disasters often strike Central America in October. In October 2001, El Salvador suffered a 7.6 magnitude earthquake. A resulting landslide buried hundreds of people in a suburb of the capital San Salvador. Environmental activists and local authorities in the town of Las Colinas said deforestation contributed to the disaster when the Supreme Court failed to stop the construction of mansions that deforested the hillside that gave way.

In 1998, a Mexican government minister said that deforestation and the spread of illegal housing worsened the devastation wrought by recent flooding in Mexico's Chiapas state. Farmers in the impoverished state cut down many trees to clear the area for new fields.

Then Social Development Minister Esteban Moctezuma Barragan said much of the destruction was "due to deforestation and the problem of irregular settlements on the edges of rivers."

But today, Patrick Durst, senior forestry officer for FAO's Regional Office for Asia and the Pacific said the issue is more complex.

Hillside cleared for pasture and degraded by livestock grazing. Monteverde, Puntarenas, Costa Rica. (Photo by Raúl Velásquez courtesy FAO)

The FAO and CIFOR say it is 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.

They point to a complex interplay of natural and man-made conditions that produce major floods and worsen their impact.

The report notes that large floods always have been a natural, 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.

Kaimowitz said, "Politicians and policymakers should stop chasing quick fixes for flood-related problems and promote integrated watershed and floodplain management."

The FAO-CIFOR report acknowledges that forests can play a role in minimizing runoff that causes localized flooding. But it concludes that "there is no evidence that a loss of trees significantly contributes to severe widespread flooding."

Even at the local level, the report notes, the flood-reducing effects of forests are dependent on soil depth and structure, and saturation levels, not exclusively on the presence of the trees.

Dr. Pal Singh of the World Agroforestry Center said, "We need to stop blaming people who live and work in and around forests for floods that affect entire river basins, and instead consider the effect of a wide variety of land-use issues, which can in some instances include poor logging techniques. Policy makers and development agencies have a moral and ethical responsibility to pursue solutions that are rooted in the best available science."

The World Agroforestry Centre operates to increase the use of working trees by smallholder rural households to help ensure food security, income, health, shelter, energy and a regenerated environment.

CIFOR and the World Agroforestry Centre are member institutes with the Future Harvest Center www.futureharvest.org established by the Consultative Group on International Agricultural Research, an alliance of 58 members and 15 Future Harvest Centers that employs science to promote sustainable development.