This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A recent United Nations report has stated that the world will likely overshoot the 1.5°C target set out in the 2015 Paris Agreement by 2030. Tree planting has become one of the most appealing symbols of climate action.
It can be easily accounted for, is visible and easy to communicate: More trees mean more carbon being absorbed and a cooler planet. Global initiatives now promise restoration on a vast scale, including the Bonn Challenge goal of restoring 350 million hectares (865 million acres) of degraded and deforested land by 2030. But a tree is not automatically a climate solution, and land without dense tree cover is not necessarily degraded.
When tree planting targets natural grasslands, shrublands and savannas, well-meaning efforts can replace one ecosystem with another, reduce water availability and threaten livelihoods. In 2007, the African Union launched the Great Green Wall Initiative, a plan to stop the southern expansion of the Sahara Desert by planting trees and restoring landscapes across 22 countries from Senegal to Djibouti. Yet, almost 20 years later, the initiative has had mixed results.
What truly works is simple: Plant trees for restoration in the right ecosystems. Drylands, including grasslands, shrublands and savannas, are often characterized by what they seem to lack: water, dense vegetation or agricultural potential. Yet they cover about 40% of Earth's surface, support billions of people and play an important role in the year-to-year variability of the global carbon cycle—changes in the carbon absorbed and released from one year to the next.
Dryland ecosystems have evolved around low and highly variable rainfall, recurrent drought and disturbance. Native grasses, shrubs, scattered trees and biological soil crusts are not signs of an ecosystem needing restoration. They are parts of a functioning biome.
That distinction matters because global restoration targets can identify these naturally open ecosystems as candidates for tree cover. Ecologists have warned that planting trees in old-growth grasslands and savannas can damage biodiversity and ecosystems rather than restore them. Planting trees may result in more woody cover, but the landscape itself may experience ecological and biodiversity loss.
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