Johnny Appleseed’s heart was in the right place when he traveled across the United States planting fruit trees. However, ecologically he had room for improvement: In order to create a truly dynamic ecosystem that holds biodiversity, benefits local people, and produces a wide variety of food, a forest needs a variety of organisms. Left alone, some logged areas can recover surprisingly quickly with little help from humans, absorbing atmospheric carbon loads as they grow.
A new study from an international team of scientists, recently published in the journal Nature, finds that 830,000 square miles of deforested land in the tropics – an area larger than Mexico – could grow naturally if left alone. Five countries – Brazil, Indonesia, China, Mexico, and Colombia – account for 52 percent of the potential regrowth rate. According to the researchers, that would boost biodiversity, improve water quality and availability, and absorb 23.4 gigatons of carbon over the next three decades.
“A rainforest can grow in one to three years – it can be tough and hard to get through,” said Matthew Fagan, a conservation scientist and geographer at the University of Maryland, Baltimore County and an author of the paper. “In five years, you can have a fully enclosed canopy 20 meters high. I have walked through 80 meter high forests that are 10 to 15 years old. It just blows your mind.”
That kind of regrowth is not a given, however. First, people will have to stop using the land in intensive farming – think of the high yields due to fertilizers and other chemicals – or raising a lot of cattle, whose weight compacts the soil and makes it difficult for new plants to take root. . Cows, of course, tend to nosh on small plants.
Second, it helps that the hot soil has a high carbon content to feed the plants. “Organic carbon, as anyone who likes to compost knows, really helps the soil to be more nutritious and more fertile in terms of its water-holding capacity,” Fagan said. “We found that areas with soil like that are more likely to have forests.”
And it is beneficial for the damaged area to be close to a standing forest. That way, the birds can fly across the area, taking out seeds to eat in the forest. And when those plants grow, other tree-dwelling species like monkeys can eat their fruit and spread the seeds, too. This starts a self-reinforcing cycle of biodiversity, leading to one of those 80 meter tall forests that is only ten years old.
The more biodiversity there is, the more resilient the forest is to shocks. For example, if a species disappears due to disease, another similar species may fill the gap. That’s why planting a bunch of the same tree species – Ã la Johnny Appleseed – pales in comparison to the rainforest variety that returns naturally.
“When you have that diversity in the system, they tend to do better in the environment, and they tend to be more resilient,” said Peter Roopnarine, a biologist at the California Academy of Sciences, who studies climate impacts. in ecosystems but did not contribute to the new paper. “Unless or until we can match that natural complexity, we will always be a step behind what nature does.”
Governments and non-profit organizations can now use data collected from this study to identify areas to prioritize for cost-effective recovery, according to Brooke Williams, a research associate at the University of Queensland and lead author of the paper. “Importantly, our data set does not tell us where it should and should not be returned,” he said, because that is a question best left to local governments. One community, for example, may rely on a plant that requires open spaces to grow. But if local people can succeed with the regrown forest – by cashing in on tourism and growing crops like coffee and cacao within the canopy, a practice known as agroforestry – their government can pay them to leave the land alone.
Susan Cook-Patton, senior reforestation scientist at the Nature Conservancy, said there are more than 1,500 species that have been used in afforestation around the world. “There are many 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 the carbon value, the biodiversity value, and the health of the people who live there?”
The tricky thing here is that the world is warming and droughts are getting worse, so the natural forest can find itself in a different situation. “We know climates will change, but there is still uncertainty about some of that change, uncertainty in our climate prediction models,” said Roopnarine.
So even though the forest is still standing, reforestation is in a sense a driving force behind environmental groups and governments. A global initiative known as the Bonn Challenge aims to restore 1.3 million square miles of degraded and logged land by 2030. So far, more than 70 governments and organizations from 60 countries, including the United States, have signed up to contribute 810,000 square miles to that target.
Sequestration of 23.4 gigatons of carbon over three decades may not sound like much in the context of humanity’s 37 annual emissions. But these are just tropical forests. Protecting temperate forests and seagrasses will take up more carbon, in addition to new techniques such as the growth of cyanobacteria. “This is one tool in the toolbox — it’s not a silver bullet,” Fagan said. “It is one of the 40 bullets needed to fight climate change. But we must use all available methods.”
This article appeared on Grist, a non-profit, independent media organization dedicated to telling the stories of climate solutions and a just future. Learn more at Grist.org.
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