Growing evidence that forests reduce flood risk

In 2007, ALERT member Corey Bradshaw and colleagues published a high-profile global analysis that suggested forests reduce flood risk. 

A tropical torrent -- flooding in the Amazon (photo by William Laurance)

However, their analysis was instantly controversial -- lauded in some quarters and attacked in others -- in part because their study used complex statistical models rather than simple experiments or direct observations to draw their conclusions. 

Now a new study appears to provide key support for Bradshaw's assertions.  Working in Peninsular Malaysia, Jie-Sheng Tan Soo and colleagues have found strong evidence that areas with more native rainforest are less prone to damaging floods in the wet season.

Specifically, the authors found that conversion of native rainforest to oil palm or rubber plantations increased the number of days of downstream flooding in 31 different areas.

Collectively, these findings are important because they provide another key economic justification for conserving native forests -- including pristine forests and those that have been selectively logged but still retain much of their original tree cover. 

Not only do such forests harbor amazing biodiversity, store large stocks of carbon, and help to drive global climate and rainfall patterns, they also have a sizable impact on flooding -- which is vital to local communities in forested regions.

Each years, destructive floods cause billions of dollars in damage to properties, crops, and livestock.  They also kill hundreds of people and displace tens of thousands more. 

With our growing human population and increasing tendency to live, build dwellings, and farm in vulnerable floodplains, floods are becoming an ever-more serious hazard. 

The poor are often forced to live in vulnerable flood-prone areas

The poor -- which are often forced to live in flood-prone areas -- are especially vulnerable.  But we all suffer from flooding via increased insurance rates and higher taxes for government disaster-aid efforts. 

With the added complications of rising sea levels and increasing extreme-weather events, flooding might cost the world $1 trillion per year by 2050, according to one analysis.

The studies by Bradshaw, Tan Soo, and colleagues show that native forests can be vital for reducing flooding in regions that receive even occasional heavy rains. 

Less native forest means more destructive flooding -- and that's not good for any of us.