Johnny Appleseed’s heart was in the right place when he walked across the early United States planting fruit trees. However, from an ecological point of view, there was room for improvement: to create truly dynamic ecosystems that host a large amount of biodiversity, benefit local people and produce many different foods, a forest needs a wide variety of species. Left alone, some deforested areas can recover surprisingly quickly with minimal help from humans, sequestering large amounts of atmospheric carbon as they grow.

New research from an international team of scientists, recently published in the journal Naturefinds that 830,000 square miles of deforested land in humid tropical regions (an area larger than Mexico) could regrow naturally if left alone. Five countries (Brazil, Indonesia, China, Mexico and Colombia) represent 52 percent of the estimated growth potential. According to researchers, this would increase biodiversity, improve water quality and availability, and absorb 23.4 gigatonnes of carbon over the next three decades.

“A rainforest can emerge in one to three years; it can be overgrown and difficult to get through,” said Matthew Fagan, a conservation scientist and geographer at the University of Maryland, Baltimore County and co-author of the paper. “In five years, you will be able to have a fully enclosed canopy that is 20 feet tall. I have walked through 80 foot tall rainforests that are 10-15 years old. “It just blows your mind.”

However, that type of resurgence is not a fact. First, humans would have to stop using land for intensive agriculture (think big yields from fertilizers and other chemicals) or for raising livestock, whose weight compacts the soil and makes it difficult for new plants to take root. . Cows, of course, also tend to eat young plants.

Second, it helps that tropical soil is high in carbon to nourish plants. “Organic carbon, as anyone who loves composting knows, really helps make soil nutritious and increases its ability to retain water,” Fagan said. “We found that in places with soils like that, forests are much more likely to appear.”

And it is also beneficial for a degraded area to be close to a standing tropical forest. That way, the birds can fly around the area and defecate the seeds they have eaten in the forest. And once those plants become established, other tree-dwelling animal species, such as monkeys, can feast on their fruits and spread seeds as well. This starts a cycle of biodiversity that reinforces itself, resulting in one of those 80-foot-tall forests that’s only a decade old.

The more biodiversity there is, the more a forest can resist crises. If one species disappears due to disease, for example, another similar species could fill the gap. That’s why planting a group of trees of the same species, Johnny Appleseed style, pales in comparison to a diverse, naturally returning rainforest.

“When you have that biodiversity in the system, it tends to be more functional in an ecological sense and it tends to be more robust,” said Peter Roopnarine, a paleoecologist at the California Academy of Sciences, who studies the impact of climate. on ecosystems but was not involved in the new paper. “Unless or until we can match that natural complexity, we will always be one step behind what nature is doing.”

Governments and nonprofits can now use the data collected from this research to identify places to prioritize for cost-effective restoration, according to Brooke Williams, a researcher at the University of Queensland and lead author of the paper. “It’s important to note that our data set doesn’t tell you where you should and shouldn’t restore,” he said, because that question is best left to local governments. A community, for example, might depend on a crop that requires open space to grow. But if locals can thrive with a regenerated rainforest (for example, by making money from tourism and growing crops like coffee and cocoa within the canopy, a practice known as agroforestry), their government could pay them to leave the area alone.

Susan Cook-Patton, senior forest restoration scientist at the Nature Conservancy, said more than 1,500 species have been used in agroforestry around the world. “There are a lot of fruit trees, for example, that people use and trees that provide medicinal services,” Cook-Patton said. “Are there ways we can help shift agricultural production towards more trees and increase the carbon value, the biodiversity value and the livelihoods of the people who live there?”

The complicated thing here is that the world is warming and Droughts are getting worseso a forest that grows back naturally could soon find itself in different circumstances. “We know that climate conditions are going to change, but there is still uncertainty around some of those changes, uncertainty in our climate projection models,” Roopnarine said.

So while a forest is largely stationary, reforestation is, in a sense, a moving target for environmental groups and governments. A global goal known as the Bonn challenge aims to restore 1.3 million square miles of degraded and deforested land by 2030. So far, more than 70 governments and organizations from 60 countries, including the United States, have pledged to contribute 810,000 square miles toward that goal.

Sequestering 23.4 gigatonnes of carbon over three decades may not seem like a big deal in the context of humanity. 37 gigatonnes of emissions each year. But these are only the forests of tropical regions. Protecting temperate forests and seagrasses would sequester even more carbon, in addition to novel techniques such as growing cyanobacteria. “This is just another tool in a toolbox, it’s not a silver bullet,” Fagan said. “It is one of the 40 bullets necessary to fight climate change. But we need to use all available options.”

This article originally appeared on Grindingan independent, nonprofit media organization dedicated to telling stories about climate solutions and a just future. Get more information at Grist.org.