Letting Tropical Forests Regrow Naturally Is Up to 96% Cheaper Than Planting Trees, Study Finds

Letting tropical forests regrow on their own is far cheaper than replanting them, and can still deliver strong carbon and biodiversity benefits, a study from the University of Queensland and the University of Newcastle in Australia has found. The research, published in Nature Ecology & Evolution, mapped how the costs and benefits of natural forest regeneration vary across the tropics and found it can be up to 96% cheaper than tree-planting programs.

"Nature is a great gardener. Sometimes we just need to get out of its way while providing a bit of support," said Jiaqi Li, a PhD candidate at Queensland's School of the Environment and the study's lead author. Tree planting requires buying seeds and paying people to plant and manage them, she said, while natural regeneration mainly needs invasive species removed, seed sources nearby, and protection from fire, grazing animals and people — after which it is largely self-sufficient.

Between 2000 and 2012, tropical forests worldwide shrank by 2.3 million square kilometers, releasing an estimated 0.86 gigatons of carbon a year and threatening the roughly 1.5 billion people who depend on forests. Tropical forests cover 18% of Earth's land but hold more than half of all land vertebrate species, Li said.

The study identified "holistic hotspots" — high carbon benefits, high biodiversity benefits and low restoration costs — mostly in Indonesia, Madagascar, the Philippines, Mexico and Malaysia. Carbon benefits were strongest in the Amazon basin and in Borneo, Sumatra and Papua New Guinea, while biodiversity benefits were greater in Madagascar and other Afrotropical areas.

Senior author Brooke Williams of the University of Newcastle said the findings matter because nations have pledged under the 2022 Kunming-Montreal Global Biodiversity Framework to restore 30% of Earth's degraded land, though restoration budgets are limited. Co-author Matthew Luskin of the University of Queensland said the work would help countries decide where and how to invest based on their goals and resources.