Tuesday, October 09, 2007

Conserving Forests Saves Lives & Property From Flooding

A new study has provided solid and intriguing data to support the idea that conserving forests helps reduce the frequency and severity of flooding.
Here are two outstanding summaries of the study, from the good folks at (1) Mongabay.com and (2) The Natural Patriot.

An excerpt from the latter:

Deforestation has accelerated tremendously in recent decades, with many costs in terms of lost biodiversity, loss of soil fertility, and so on. Forests are also widely believed to protect lowlands against flooding, but this idea has been controversial. The authors of the new study compiled data from 1990 through 2000 from 56 developing countries, and used various sophisticated statistical techniques to show that (1) the frequency of floods is lower in areas with greater natural forest cover, and (2) floods are more frequent in areas that have experienced greater losses of natural forest area. Importantly, these results remained strong even after controlling statistically for effects of rainfall, slope, and area of degraded landscape. Surprisingly, despite the fact that the study compared a wide range of forest types across a global area, with all kinds of other factors that might potentially obscure these trends, the best models nevertheless accounted for more than 65% of the variation in flood frequency, and roughly 14% was explained by forest cover variables alone. And here’s the kicker:

“During the decade investigated, nearly 100 000 people were killed and 320 million people were displaced by floods, with total reported economic damages exceeding US$1151 billion . . . Based on an arbitrary decrease in natural forest area of 10%, the model-averaged prediction of flood frequency increased between 4% and 28% among the countries modeled. Using the same hypothetical decline in natural forest area resulted in a 4–8% increase in total flood duration. These correlations suggest that global-scale patterns in mean forest trends across countries are meaningful with respect to flood dynamics.”

The bottom line, therefore, is that rampant forest loss is likely to exacerbate the frequency of flood-related disasters, potentially impacting millions of poor people throughout the world, and causing trillions of dollars (yes, that’s a “t”) in damage in developing economies in the coming decades. This synthesis of global data emphasizes that protection of existing forests and active reforestation of appropriate degraded land may reduce flood-related catastrophes.

So now, conservationists devising programs to pay landowners to maintain the service of flood-protection provided by intact forests have fresh data to justify these investments. Key remaining questions include (1) who pays (2) how much (3) to whom, and (4) for how long?

While the answers are likely to vary from one location to the next, I look forward to following developments in this exciting and crucial quest to make conservation profitable.

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