Story at a glance…

• Reforestation is key to fighting the effects of climate change, yet not all strategies of reforestation have equal outcomes.

• Multiple studies show natural forest regeneration is cheaper, sequesters more carbon, and maintains more biodiversity, than hand planted forests.

• The Brazilian Atlantic Forests are being zeroed in on as a prime candidate for a massive case of letting nature take its course.

Since the early years of the 21st century, ideas about reforestation have taken root around the world as climate change moved further and further into a place of principality in the domain of development policy.

Now a decade after mass tree planting began in earnest across the world in the name of preventing climate change, a body of research indicates humanity has likely, and perhaps unsurprisingly, gotten it all wrong. Naturally regenerated forests are much better ways of achieving climate targets than mass planting.

A report from Forest News finds that Brazil’s Atlantic Forest, the oft-ignored, great forest habitat in the country, is a prime candidate for natural regeneration strategies.

Home to a wealth of biodiversity that includes ocelots and golden lion tamarins, the Atlantic Forest biome is recognized as a UNESCO Biosphere Reserve and a Brazilian Natural Heritage site. However, it has lost nearly 80% of its original area due to logging and agricultural expansion, making it ideal for restoration initiatives, reports a study from 2018.

In a separate study, seeking to map and quantify the potential for natural forest regeneration in the Atlantic Forests, the researchers found that of the current forest cover, which is around 34.1 million hectares (131,000 square miles) 8% was regenerated naturally between 1996 and 2015, but that another 20 million hectares could be reforested with a mix of natural and assisted strategies, between now and 2035, all the while saving around $90 billion in operation costs.

The savings in dollars is key, since natural forest regeneration efforts are reported to only account for 2% of the total climate change funding in the world.

Is letting nature take its course really the best bet with such tight climate deadlines? Part of the conversation has to involve a second look at mass manual-planting strategies.

Planting a dead-end

Early progenitors of the idea that climate change could be sequestered away in the roots of a trillion trees began planting seedlings by hand in massive numbers.

Africa’s Great Green Wall, as well as mass tree planting in countries like Ethiopia, China, Pakistan, and India, and rewilding efforts across Europe have greatly increased forest cover over the years. The Bonn Challenge to restore 350 million hectares of degraded land has received 210 million hectares of “pledged” reforestation efforts by more than 60 countries.

Yet issues with mass tree planting remain. A BBC report notes several massive flaws in simple goals like Trillion Trees Initiative, or the Bonn Challenge. One study cited found that 80% of the new pledges were simply plantations of rubber or other monocrop forest products, while another found that government incentives in Chile towards tree planting led to landowners clear cutting native forest are replanting it with monocrop trees just to get their hands on the government handout.

Beyond all that, the amount of CO2 capable of being sequestered in these sorts of forests have likely been overestimated, for example in Chile or in China, where the scientists found that soil samples were deeply lacking in carbon.

Lastly, hand planting seedlings is expensive. One study found that tree planting and soil preparation can cost on average between $1,400 and $34,000 per hectare.

“You need to invest in infrastructure, [nurseries, seeds, fertilizer]” Manuel Guariguata, a principal scientist at the Center for International Forestry Research (CIFOR), tells Lilly Hess of Landscape News. “You may need to transport seedlings from one site to another, and if you don’t [invest in infrastructure] well, your seedlings will die when they arrive [at the planting site] because of the mechanical vibrations in the car or truck”.

Letting nature take its course

Several small examples of natural reforestation in Ireland and the UK, two nations keen on restoring past versions of their ecosystems, show the breadth of success one can have if one simply lets nature take its course.

The rewilding project on the 3,500 acres of Knepp Estate has created one of the most biodiverse ecosystems in lower England, while a 600 year-old 1,600 acre-estate in south Ireland has achieved something similar.

Natural regeneration has this potential, unsurprisingly, of restoring far more biodiversity, especially if helped along with seed dispersion, de-weeding, and other simple management strategies. A meta-analysis found as much, when it looked at 133 papers on the topic and found that forest areas freed from agriculture and allowed to regenerate created 56% greater species richness in all categories of animals, and in five measures of vegetation structure: cover, density, litter, biomass, and height.

“Instead of conserving with specific species in mind where you’re focusing on keeping a habitat, locking it down as it is, so that that preserves the numbers of certain species, what we’ve done here is just taken our hands off the steering wheel and just stood back and let nature take over,” said Isabella Tree, co-director of the rewilding project on the Knepp Estate.

Another benefit is that naturally occurring forests trap far more carbon in the soil on average, as one study found that regenerated forests absorb 32% more carbon above ground, and sequester 11% more below, than is generally estimated by the Intergovernmental Panel on Climate Change.

For these regenerated forests to last, however, the scientists and policy makers need to know the best way for locals and other interest groups to be motivated enough to leave the regenerating forests intact long-term.

The Forest News article suggests that schemes like a payment system for rural dwellers who leave or protect and maintain stands of regenerated forests, or increased access to investment capital for agroforestry production, could be used to help convince those who rely on rural areas to leave the trees alone rather than turning them into wood chips.

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