Given a chance, forests bounce back

Could doing nothing help the environment?

Well, not really doing nothing. But in this case leaving land alone so that it can return to forest. 

A study in the journal Science, published last week, showed the surprisingly quick return of land to a healthy forested state if simply left alone. Under the right conditions, forests can reemerge from land that has been exploited by humans.

Tropical forests are disappearing around the world at an alarming rate. At the recent climate conference in Glasgow, Scotland, world leaders promised to halt deforestation by the end of this decade. 

Commitments to planting millions of trees have been made as part of the effort to absorb carbon from the atmosphere and provide other beneficial environmental effects, including greater biodiversity.

But these efforts can be costly; in some cases, a high percentage of the new seedlings die. 

This study suggests that under the right conditions, tree planting could be greatly augmented by simply protecting land that has been cleared of trees for agricultural or other human use and allowing it to return to a forested condition.

Forests are far more than collections of trees. They are complex networks of life that include a wide variety of plants, animals, and microbes.

Ideally, the abandoned land most suited to quick reforestation should have soil whose nutrients have not been totally exhausted, and should be located near other forested areas.

Allowing land to return to a forested condition on its own provides a “cheap, natural solution” to the urgent problems of diminishing biodiversity and climate change, says Lourens Poorter of Wageningen University in the Netherlands, who participated in the study. As trees grow, for example, they produce leaf litter, which in turn improves soil quality as it decomposes.

In the world’s tropics, forests are already rejuvenating themselves on about 3 million square miles of former farm or ranch land, the authors say. Protecting this process will be a critical part of regrowing forests.

The scientists’ research is also confirmed by the track record of forest regrowth that has been observed over long periods, they note, such as in Europe during the 18th and 19th centuries and in the Northeastern U.S. in the early 20th century, where large tracts of land, once cleared for farming, have returned to healthy forest.

What surprises the researchers is how quickly such recovery can take place.

“My plea is to use natural regrowth where you can, and plant actively and restore actively where you need to,” Dr. Poorter says.

Sometimes just keeping hands off may be the best way to help.