Johnny Appleseed’s heart was in the right place when he traveled the early states of the United States planting fruit trees. Ecologically, however, there was room for improvement: to create truly vibrant ecosystems that host great biodiversity, benefit the local population, and produce many different foods, a forest needs a wide variety of ‘species. Left to their own devices, some deforested areas can bounce back 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 Naturereveals that 830,000 square miles of deforested land in the humid tropics – an area larger than Mexico – could grow back naturally if left to their own devices. Five countries – Brazil, Indonesia, China, Mexico and Colombia – account for 52 percent of the estimated potential regrowth. According to the researchers, this would boost biodiversity, improve water quality and availability and absorb 23.4 gigatons of carbon over the next three decades.

“A rainforest can spring up in one to three years — it can be scrubby and difficult to pass 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 completely enclosed canopy 20 feet high. I walked through rainforests that were 80 feet tall and 10-15 years old. It blows your mind.

This kind of regrowth is not obvious, however. First, humans should stop using land for intensive agriculture – think big yields from fertilizers and other chemicals – or to raise hordes of livestock, whose sheer weight compacts the soil and makes it difficult rooting of new plants. . Of course, cows also tend to nibble on young plants.

Second, it is helpful for tropical soils to have high carbon content to nourish plants. “Organic carbon, as anyone who loves composting knows, really helps the soil be nutritious and strengthen in terms of its ability to hold water,” Fagan said. “We found that places with soils like this are much more likely to see forests appear.”

And it is also beneficial if a degraded area is near a tropical forest. This way, birds can fly through the area and poop seeds they ate in the forest. And once these plants are established, other arboreal animal species, like monkeys, can also feast on their fruits and spread seeds. This initiates a self-reinforcing cycle of biodiversity, resulting in the creation of one of these 80-foot-tall forests that is only ten years old.

The more biodiversity there is, the more a forest can withstand shocks. If one species goes extinct due to disease, for example, another similar species could fill the void. This is why planting a group of trees of the same species – a la Johnny Appleseed – is nothing compared to a diverse rainforest that returns naturally.

“When you have this 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 the climate. on ecosystems but was not involved in the new document. “Unless or until we can match this natural complexity, we will always lag behind what nature does.”

Governments and non-profit organizations can now use the data collected from this research to identify locations 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 dataset doesn’t tell us where should or shouldn’t be restored,” she said, because that’s a question best left to local governments. A community, for example, might depend on a crop that requires open spaces to grow. But if locals can prosper with a regenerated rainforest – for example by earning money from tourism and growing crops like coffee and cocoa in 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 worldwide. “There are, for example, a lot of fruit trees that people use and trees that provide medicinal services,” Cook-Patton said. “Are there ways to 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 problem here is that the world is getting warmer and droughts are getting worseso a naturally regrowing forest may soon find itself in different circumstances. “We know that climate conditions are going to change, but there is still uncertainty about some of these changes, uncertainty in our climate projection models,” Roopnarine said.

So even if a forest is very stationary, reforestation is, in a sense, a moving target for environmental groups and governments. A global goal known as the challenge of Bonn aims to restore 1.3 million square kilometers of degraded and deforested land by 2030. So far, more than 70 governments and organizations from 60 countries, including the United States, have committed to contributing to this goal on 810,000 square kilometers.

Sequestering 23.4 gigatons of carbon over three decades may not seem like much in the context of humanity. 37 gigatons of emissions each year. But this is only the forests of tropical regions. Protecting temperate forests and seagrass meadows would capture even more carbon, complementing cutting-edge techniques such as growing cyanobacteria. “It’s a tool in a toolbox – it’s not a silver bullet,” Fagan said. “This is one of the 40 bullets needed to fight climate change. But we must use all available options.