News Feature: The best strategy for using trees to improve climate and ecosystems? Go natural

Starting in 1985, 20 years of regeneration transformed barren, degraded land in the African Burkina Faso village of Ranawa into a fertile farm. Image credit: Chris Reij (World Resources Institute, Washington, DC).

Despite big headlines and big money devoted to massive tree-planting projects that pledge to stave off desertification, the most effective method may be nurturing native seeds, rootstocks, and trees.

John Carey – PNAS March 3, 2020 117 (9) 4434-4438; https://doi.org/10.1073/pnas.2000425117https://www.pnas.org/content/117/9/4434

Near the start of the rainy season in June 1983, Tony Rinaudo hauled a load of trees in his truck to be planted in remote villages in the Maradi region of Niger. Driving onto sandy soil, Rinaudo stopped to let air out of his tires to get better traction, and was hit by a sense of futility. For years, the Australian missionary had been working to improve the lives of people in one of the poorest countries in Africa by planting trees. But it wasn’t working. Most of the trees died or were pulled out by farmers. Standing beside his truck, all he could see was dusty barren plain, broken by a few scraggly bushes. “It dawned on me that I was wasting my time,” he says.

A man of deep faith, Rinaudo asked God for guidance. In a moment of clarity, his eye caught sight of one of the bushes. At closer look, he realized that it was no mere bush or weed; instead, it was a potentially valuable native tree—if permitted to grow. There was no need to plant trees; they were already there. “At that moment everything changed,” he says. Even a seeming desert harbors tree stumps, roots, and seeds that can be encouraged and nurtured—“a treasure chest waiting to be released,” says Rinaudo. “And if you allow some trees to grow, amazing things happen.”

Rinaudo’s epiphany led local farmers to add at least 200 million trees across more than seven million hectares in Niger—at up to 60 trees per hectare. The crucial twist: They did so without planting any new trees.

The regreening brought “spectacular” results in terms of crop yields and farmers’ incomes, reports a 2019 article (1), and the idea was used in other regions such as northern Ethiopia, where, over the course of several years, long-dormant springs bubbled to life and living standards climbed as nascent forests captured water, improved soil fertility, and boosted crop yields. The collective effort has been one of the most effective responses to the growing problem of the degradation of the world’s drylands (those limited by water scarcity but capable of supporting some vegetation), such as the Sahel region of Africa, says Tim Christophersen, head of United Nations (UN) Environment Programme’s Freshwater, Land, and Climate Branch. “It all came together in a perfect storm of success.”

Yet these results were largely unknown or simply unaccepted for years by governments and international aid organizations in the battle to restore the world’s drylands to fertile lands and to combat so-called “desertification”—the perceived threat of an encroaching desert. Instead, large—and some say flawed—tree-planting efforts often were chosen.

But the idea of nurturing native greenery is now gaining traction—and that, proponents say, will open the door to restoring vast areas of degraded lands, improving livelihoods of millions of smallholder farmers, reducing migrations of impoverished populations, and fighting climate change by soaking up carbon dioxide. “We’re passing a tipping point, where the idea of natural regeneration is really beginning to snowball,” says Dennis Garrity, Drylands Ambassador for the United Nations Convention to Combat Desertification.

Not Easy Staying Green

Historically, big-ticket tree-planting projects, not natural regeneration, have reaped most of the attention and support globally. In the mid-1980s, Burkina Faso’s president Thomas Sankara proposed planting a line of trees 7,000 kilometers long across Africa in a “Great Green Wall” to hold back what was thought to be relentlessly spreading sands, and the Green Wall idea was resurrected by Olusegun Obasanjo, president of Nigeria, in 2005 (1). In June 2019, Ethiopia’s minister of innovation and technology, Getahun Mekuria, claimed that his country had set a new record for the number of trees planted in one day, 353 million, garnering headlines (and skepticism) around the world (23).

The focus on tree planting to fight desertification has two main problems, experts now say. First, the Sahara Desert isn’t expanding, as was feared to be the case during droughts in the 1960s and 70s—and second, planting trees wouldn’t be a solution, in part because the track record for projects to plant trees is so poor. “In the Sahel, the Pavlovian reaction has been to say, ‘let’s plant trees,’” says geographer Chris Reij, a senior fellow at the World Resources Institute (WRI) in Washington, DC. “But it has had disappointing results.” Studies in Kenya and Senegal show that the mortality of the planted trees is high—80% or more (4).

The many reasons for poor survival of trees include lack of watering and proper care, cutting trees for firewood, clearing trees for planting crops, little ownership of trees by local farmers, and mismatches between the species planted and local conditions. “It’s easy to entice people to plant trees, by paying or having a big campaign like Ethiopia’s,” explains Graham Wynne, advisor to the UN Global Commission on Adaptation. “But the trees require watering and nurturing for years, and getting people to do that, especially when the trees may be miles from their houses, just doesn’t work.” The main successes for tree planting are seen in commercial plantations for timber harvest, not restoring degraded lands.

The big, expensive tree-planting projects purportedly aimed at land restoration still continue, however, whereas the idea of naturally regenerating trees that are cared for by local communities typically has gotten short shrift, says Reij. “Too few people know the story.”

Planting the Seed

For years, Rinaudo has been trying to tell that story. Now at World Vision Australia, a Christian humanitarian organization based in Melbourne, he is bringing the approach to 27 countries and is finally winning international recognition (56). Under the African Forest Landscape Restoration Initiative (AFR100), 28 countries have committed to restoring 113 million hectares with various approaches, and in the last couple of years the Great Green Wall effort has shifted its focus: less tree planting, and more work with local communities to promote natural regeneration. “We moved the vision of the Great Green Wall from one that was impractical to one that was practical,” says Mohamed Bakarr, the lead environmental specialist for Global Environment Facility (7).

Deep planting pits filled with manure and other organic matter, a traditional technique called zaï, has brought life back to hard, barren lands in Africa’s Sahel region. Image credit: Chris Reij (World Resources Institute, Washington, DC).

At Climate Week in September 2019, Garrity and a group he chairs called the Global EverGreening Alliance launched an effort to massively scale up the approach to capture significant carbon emissions at a fraction of the cost of other solutions such as alternative energies. And the World Bank, long wedded to big tree-planting projects, is beginning to switch to land restoration efforts based on natural generation. “All of a sudden the major giant donors are waking up,” says Rinaudo.

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Author: Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.