Johnny Appleseed’s heart was in the right place when he went across the United States planting fruit trees. Ecologically, however, there has been room for improvement: to create truly dynamic ecosystems that host a lot of biodiversity, benefit local people and produce lots of different foods, a forest needs a wide variety of species. Left alone, some cleared areas can recover surprisingly quickly with minimal help from humans, sequestering loads 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 the humid tropics—an area larger than Mexico—could regenerate naturally if left to its own devices. Five countries – Brazil, Indonesia, China, Mexico and Colombia – account for 52 percent of the estimated potential growth. According to the researchers, this would boost biodiversity, improve water quality and availability, and sequester 23.4 gigatons of carbon over the next three decades.

“A rainforest can emerge in one to three years — it can be bushy and hard to walk 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 can have a fully enclosed canopy that’s 20 feet tall. I walked in 80 foot tall rainforests that are 10 to 15 years old. It just blows your mind.”

However, this type of regrowth is not a given. First, people would have to stop using the land for intensive agriculture—think high yields thanks to fertilizers and other chemicals—or raising cattle herds, whose sheer weight compacts the soil and makes it difficult for new plants to take root. . Cows, of course, also tend to find the young plants.

Second, it helps keep tropical soil high in carbon to feed plants. “Organic carbon, as anyone who loves composting knows, really helps the soil to be nutritious and increase its water-holding capacity,” Fagan said. “We found that places with soils like this are much more likely to grow forests.”

And it is also beneficial for a degraded area to be near a standing rainforest. This way the birds can fly around the area, picking up the seeds they have eaten in the forest. And once these plants are established, other species of tree-dwelling animals, such as monkeys, can feast on their fruits and spread seeds as well. This initiates a self-reinforcing cycle of biodiversity, resulting in one of those 80-foot tall forests that is only a decade old.

The greater the biodiversity, the more a forest can withstand shocks. If a species disappears due to disease, for example, another similar species could fill the gap. That’s why planting a bunch of the same species of trees – at Johnny Appleseed – pales in comparison to a diverse, naturally regenerating rainforest.

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

Governments and nonprofits can now use the data gleaned 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. “Importantly, our data set does not inform where it should and should not be restored,” she said, because that is a question best left to local governments. A community, for example, might rely on a culture that requires open spaces to grow. But if locals can thrive with a regrown rainforest — for example, by making money from tourism and growing crops like coffee and cocoa inside the tree, 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 worldwide. “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 to more trees and increase carbon value, biodiversity and the livelihoods of the people who live there?”

The most complicated thing here is that the world is warming and droughts are getting worseso a naturally regrowing forest might soon find itself under different circumstances. “We know that climate conditions are going to change, but there’s still uncertainty with some of those changes, uncertainty in our climate projection models,” Roopnarine said.

So while a forest is very stationary, reforestation is, in a way, a moving target for environmental groups and governments. A global goal known as The challenge from Bonn aims to restore 1.3 million square miles of degraded and deforested land by 2030. To date, more than 70 governments and organizations in 60 countries, including the United States, have signed on to contribute 810,000 miles squares to this objective.

Sequestering 23.4 gigatons of carbon over three decades may not sound like much in the context of humanity. 37 gigatons of emissions every year. But these are only the forests of tropical regions. Protecting temperate forests and seagrasses would capture even more carbon, in addition to new techniques such as growth of cyanobacteria. “This is one tool in a toolbox — it’s not a silver bullet,” Fagan said. “It is one of the 40 bullets needed to fight climate change. But we have to use all the options available.”

This article originally appeared in groatsa nonprofit, independent media organization dedicated to telling stories about climate solutions and a just future. Learn more at Grist.org.