Johnny Appleseed’s heart was in the right place when he walked all over the early United States to plant fruit trees. Ecologically, however, he had room for improvement: To create truly dynamic ecosystems that host a lot of biodiversity, benefit local people and produce many different foods, a forest needs a wide variety of species. Left to their own devices, some deforested 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 humid tropical regions—an area larger than Mexico—can regrow naturally if left to its own devices. Five countries – Brazil, Indonesia, China, Mexico and Colombia – account for 52 percent of the estimated potential regrowth. According to the researchers, this will 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 brushy and difficult to walk through,” said Matthew Fagan, a conservation scientist and geographer at the University of Maryland, Baltimore County and a co-author of the paper. . “In five years, you could have a fully enclosed canopy that is 20 feet high. I have walked in 80 foot tall rainforests that are 10 to 15 years old. It just blows your mind.”
However, that kind of regrowth is not a given. First, people will have to stop using the land for intensive agriculture – think big yields thanks to fertilizers and other chemicals – or raising piles of cattle, the sheer weight of which compacts the soil and makes it difficult for new plants to take root. Of course, cows also tend to nose on young plants.
Second, it helps tropical soil to have a high carbon content to feed plants. “Organic carbon, as anyone who likes compost knows, really helps the soil to be nutritious and build itself up in terms of its ability to hold water,” Fagan said. “We found that places with such soil are much more likely to have forests emerging.”
And it is also beneficial for a degraded area to be near a standing tropical forest. That way, birds can fly over the area and blow out seeds they have eaten in the forest. And once those plants are established, other tree-dwelling animal species like monkeys can feast on their fruits and also spread seeds. This starts a self-reinforcing cycle of biodiversity, leading to one of those 80-foot tall forests that are only a decade old.
The more biodiversity, the more a forest can withstand shocks. For example, if one species disappears due to disease, another similar one can fill the void. That’s why planting a bunch of the same tree species — à la Johnny Appleseed — pales in comparison to a diverse rainforest that comes back naturally.
“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,” says Peter Roopnarine, a paleoecologist at the California Academy of Sciences , which studies the impact of the climate. on ecosystems, but was not involved in the new paper. “Unless or until we can match that natural complexity, we’re always going to be a step behind what nature does.”
Governments and nonprofits can now use the data gathered from this research to identify places to prioritize for cost-effective restoration, according to Brooke Williams, a research associate at the University of Queensland and the paper’s lead author. “Importantly, our data set does not provide information about where to repair and not,” she said, because that is a question best left to local governments. For example, one community may rely on a crop that requires open spaces to grow. But if the local population can thrive with a regrown tropical forest—for example, by making money from tourism and growing crops like coffee and cocoa within the canopy, a practice known as agroforestry—their government can pay them to leave the area alone. too late
Susan Cook-Patton, senior forest restoration scientist at the Nature Conservancy, said that more than 1,500 species have been used in agroforestry worldwide. “For example, there are many fruit trees 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 boost the carbon value, the biodiversity value and the livelihoods of the people who live there?”
The tricky bit here is that the world is warming and droughts worsenthus, a naturally regrowing forest may soon find itself in different circumstances. “We know the climate conditions are going to change, but there’s still uncertainty with some of that change, uncertainty in our climate projection models,” Roopnarine said.
So, while a forest is very 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 signed on to contribute 810,000 square miles to that target.
Sequestering 23.4 gigatons of carbon over three decades may not sound like much in the context of humanity’s 37 gigatons of emissions each year. But these are only the forests in tropical regions. Protecting temperate forests and seagrasses will capture even more carbon, in addition to new techniques such as growing cyanobacteria. “It’s one tool in a toolbox — it’s not a silver bullet,” Fagan said. “This is one of 40 bullets needed to fight climate change. But we have to use all available options.”
