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Two workers handle tree saplings being grown to reforest burned areas of Indonesia
Reforesting of burnt areas in Kalimantan province, Indonesia.Credit: Kadir van Lohuizen/NOOR/eyevine
Manter o aquecimento global abaixo de 1,5 ° C para evitar mudanças climáticas perigosas1 exige a remoção de grandes quantidades de dióxido de carbono da atmosfera, bem como cortes drásticos nas emissões. O Painel Intergovernamental sobre Mudanças Climáticas (IPCC) sugere que cerca de 730 bilhões de toneladas de CO2 (730 petagramas de CO2, ou 199 petagramas de carbono, Pg C) devem ser retirados da atmosfera até o final deste século2. Isso é equivalente a todo o CO2 emitido pelos Estados Unidos, o Reino Unido, a Alemanha e a China desde a Revolução Industrial. Ninguém sabe capturar tanto CO2.
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Forests must play a part. Locking up carbon in ecosystems is proven, safe and often affordable3. Increasing tree cover has other benefits, from protecting biodiversity to managing water and creating jobs.
The IPCC suggests that boosting the total area of the world’s forests, woodlands and woody savannahs could store around one-quarter of the atmospheric carbon necessary to limit global warming to 1.5 °C above pre-industrial levels2. In the near term, this means adding up to 24 million hectares (Mha) of forest every year from now until 2030.

Policymakers are sowing the seeds. For example, in 2011, the German government and the International Union for Conservation of Nature launched the Bonn Challenge, which aims to restore 350 Mha of forest by 2030. Under this initiative and others, 43 countries across the tropics and subtropics where trees grow quickly, including Brazil, India and China, have committed nearly 300 Mha of degraded land (see Supplementary Information, Table S1). That’s encouraging.
But will this policy work? Here we show that, under current plans, it will not. A closer look at countries’ reports reveals that almost half of the pledged area is set to become plantations of commercial trees (see Table S1). Although these can support local economies, plantations are much poorer at storing carbon than are natural forests, which develop with little or no disturbance from humans. The regular harvesting and clearing of plantations releases stored CO2 back into the atmosphere every 10–20 years. By contrast, natural forests continue to sequester carbon for many decades4.

To stem global warming, deforestation must stop. And restoration programmes worldwide should return all degraded lands to natural forests — and protect them. More carbon must be stored on land, while recognizing competing pressures to deliver food, fuel, fodder and fibre.
We call on the restoration community, forestry experts and policymakers to prioritize the regeneration of natural forests over other types of tree planting — by allowing disturbed lands to recover to their previous high-carbon state. This will entail tightening definitions, transparently reporting plans and outcomes and clearly stating the trade-offs between different uses of land.

Misdirected efforts

To combat climate change, the most effective place to plant trees is in the tropics and subtropics — this is where most forest-restoration commitments are found. Trees grow and take up carbon quickly near the Equator, and land is relatively cheap and available (see go.nature.com/2ogmbmz and ‘Restoration potential’). Establishing forests has little effect on the albedo (reflectivity) of the land surface, unlike at high latitudes, where trees obscure snow that would otherwise reflect solar energy and help to cool the planet. Well-managed forests can also help to alleviate poverty in low-income regions, as well as conserve biodiversity and support the United Nations Sustainable Development Goals — notably, goals 1 (no poverty), 6 (clean water), 11 (sustainable communities), 13 (climate action) and 15 (life on land).