The recent explosion of interest in tree restoration has transformed the climate change conversation. Although the trillion tree campaign – 1T.org – is now in the realm of politicians and influencers (Greta Thunberg: Davos leaders ignored climate activists’ demands, 24 January), it emerged from scientific literature. But what exactly did the science show?
We estimated that there is up to 0.9bn hectares of degraded land that might support a trillion trees outside of existing forest, urban or agricultural land. Although the exact carbon storage potential is debated, scientists agree that ecosystem restoration is a powerful tool for carbon drawdown.
But with anything this powerful, the risks of getting it wrong can be huge. To avoid these risks, any organisation pledging to the trillion tree campaign should uphold these basic principles:
1) Cutting fossil fuel emissions is the priority for climate action. There is not enough room on Earth to offset all of our carbon emissions with trees. In combination with decarbonising, ecosystem restoration can be valuable for drawing down some of the excess atmospheric carbon.
2) Restoration must be ecologically responsible. Restore the right diversity of native tree species where they naturally exist. Planting trees in unsuitable ecosystems could result in unintended adverse consequences. Natural forests, grasslands, shrublands and wetlands serve as vital repositories of carbon and biodiversity to be preserved and restored. Monoculture plantations of exotic species will not likely yield the desired benefits.
3) Restoration must be socially responsible. It is crucial to uphold the rights of indigenous people and local communities, building on fair and sustainable economic models, and avoiding competition with food production. Only when local communities benefit from the economic and ecological benefits that new ecosystems provide can restoration be sustainable.
4) Conserve existing ecosystems. We are losing old forests at an alarming rate. Conserving and sustainably managing ecosystems we already have must be at the core of a global restoration movement.
These four non-exhaustive restoration principles are supported by the steering committee of the Global Forest Biodiversity Initiative – a global network of forest ecologists.
Crowther Lab, ETH Zurich
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