What is the best way to restore forests? Do nothing at all.

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Image: World Wildlife Fund

Recently, there has been a global effort to restore many of the forests devastated by human activity. In that time, active reforestation of these areas has cost millions of dollars and countless hours of labor. Unfortunately, these resources may have gone to waste. A new study suggests that the best way to restore the forests might be to do nothing at all.

The study, published in Science Advances, sought to determine the efficacy of active reforestation. To do this, the researchers performed a meta-analysis of 133 studies on the restoration of tropical forests. Their results showed that natural regeneration was more successful at restoring not only the forests but also the biodiversity.

Forests provide shelter to over 80% of the terrestrial organisms on our planet. Moreover, they are indirectly responsible for the survival of an even larger percentage of the life on Earth, including humans. Despite their importance, it is estimated that only 15% of forests have been left untouched.

Many initiatives have begun in recent years to bring back the forests. Two of the most publicized efforts, the New York Declaration on Forests and the Bonn Challenge, seek to restore a combined 500 million hectares by 2030. That represents an area about half the size of Canada.

The primary approach to meeting these sizeable goals has been the active restoration of forests. Active restoration involves treating the soil of the deforested areas and planting new trees. This type of restoration, however, uses a staggering amount of resources. The authors of the paper say that restoring a single hectare using this method could cost between $1,400 and $34,000 USD.

Despite the cost, most organizations are using active restoration. This is surprising considering that natural regeneration, the alternative approach, costs almost nothing in comparison. Natural regeneration is a hands-off method of reforestation whereby forests are allowed to grow without human interference. The resources that would have otherwise been used to restore the area are instead used to protect and preserve it.

The reason active restoration is so widely used is that it has long been thought to be more successful than natural regeneration. This study has now shown that is not the case. In all measures of success, natural regeneration outperformed active restoration. Naturally regenerated forests had an increased biodiversity and higher abundance of vegetation when compared to actively restored forests.

The authors make it clear that both methods of reforestation have their place. Neither method is sufficient for every project, and some might even demand both. They suggest that future policy on reforestation should more seriously consider the benefits of natural regeneration. Sometimes the best thing we can do for nature is to leave it alone.