World’s watersheds lost 6 percent of their forests in 14 years

The world’s 230 watersheds have critical functions in providing water to ecosystems and human communities. 

But like any natural resource, they are susceptible to degradation from a wide variety of factors from damming and local pollution to climate change.

A new analysis  finds that the world’s watersheds lost an average of 6 percent of their tree cover over 14 years – with some particularly affected areas losing up to 22 percent. 

This, the analysts says can have detrimental effects on water quality and flow, endangering water security for the global populace.

Watersheds are areas of land that slope inwards and funnel water sources together. Some – like the Mississippi drainage in the U.S., for instance – are large, comprising millions of square kilometers, while others can be quite small.

While forests themselves are mostly land-based (mangroves are an exception), they form an important component of watersheds. Their canopies release excess water via a process called evapotranspiration and shelter the ground from the eroding effects of rainfall; their roots bind soil, further helping reduce erosion, as well as filtering groundwater and recharging aquifers.

If a river loses its surrounding forest, its banks have a much higher chance of eroding, sullying its water and making its channel shallower. 

 This, in turn, could make the water warmer and lose some of its oxygen, a change that could spell doom for species that evolved over millennia to live in once-cold, clear streams.

Flooded peat forest along a river in Sumatra. Photo by Rhett A. Butler

For human communities, watershed degradation may mean reduced water quality and quantity as rivers fill with sediment and runoff pollutants, and their tributaries are stopped up by erosion.



*** Story copied from Mongabay Weekly Newsletter