Restoring the World's Forests: What Works, What Doesn't, and the Science of Recovery

In 2014, 150 countries signed the New York Declaration on Forests, committing to restore 350 million hectares of degraded and deforested land by 2030. In 2021, at COP26, over 100 countries signed the Glasgow Leaders' Declaration on Forests and Land Use. Billions of dollars have been pledged for forest restoration. Corporations have made net-zero commitments that include large-scale tree planting. The ambition is unprecedented — but the science of what actually works in forest restoration is considerably more nuanced than the political commitments suggest.

The Problem With Tree Planting

The most publicised form of forest restoration — mass tree planting — is also the most scientifically problematic. Studies have found failure rates in tree planting projects of between 40% and 90%, due to poor species selection, inappropriate site conditions, lack of post-planting maintenance, or community conflict over land use. Monoculture plantations — often used to meet restoration targets quickly — provide a fraction of the biodiversity value of natural forest and may actually suppress natural regeneration by outcompeting native species. A plantation of eucalyptus or teak is not a forest in any ecologically meaningful sense.

Natural Regeneration — The Most Effective Approach

A growing body of research indicates that allowing forests to regenerate naturally — by removing pressures such as cattle grazing and agricultural encroachment — is both cheaper and ecologically superior to active planting in most situations. A landmark global study published in Science in 2020 found that natural forest regeneration could sequester 8.9 billion tonnes of CO₂ per year if allowed to occur across all suitable areas — more than the contribution of active restoration through planting. Natural regeneration also restores biodiversity more effectively, as native species recolonise at their own pace according to local ecological conditions.