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.

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.

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.

Even in areas where the ground is so hard and dry that virtually nothing grows—“as hard and barren as your desk,” says Garrity—drylands can be restored without planting trees. Locals use an ancient technique called zaï, revived in the 1980s by a farmer in Burkina Faso named Yacouba Sawadogo. People dig deep planting pits and stuff them with manure and other organic matter (8). The holes trap water, making it possible to grow crops again, and tree seeds in the manure germinate to bring back the tree canopy.

Rinaudo’s key insight, however, was that tree stumps, roots, or seeds still exist in the soils of most degraded land in the Sahel region of Africa and in drylands around the world, just waiting for the right kind of changes in land practices (including grazing patterns and burning practices) that allow trees to grow. “Most ecosystems in the world have remnant seeds in the soil, and natural regrowth can be cheaper and more successful than tree planting,” says Christophersen.

Bringing back agroforestry and proving its benefits wasn’t easy, however. “The idea of trees being compatible with crops like sorghum, millet, and maize was basically anathema to Western agricultural science practices,” explains Garrity.

There are good reasons why traditional agriculture in the drylands of Africa typically included trees. In modern Western systems, such as the cornfields of Iowa, crops and trees on the same field would compete for water, sunlight, and nutrients during the growing season. In the drylands, in contrast, “crops only grow in the rainy season, but trees grow all year,” explains Garrity. One especially important tree, the acacia, drops its leaves during the wet season, so there’s no competition at all with crops, and it also offers a host of benefits. It grabs nitrogen from the air, helping to fertilize the soil, and provides high-protein fodder for livestock. “It’s a wonder tree,” says Garrity.

Similarly, baobab trees offer nutritious leaves and fruit, and shea trees provide oil for cooking and cosmetics. These trees also shade the soil and crops, cutting soil temperatures by as much as 36 °C and increasing the humidity in the crop canopy, thereby promoting crop growth. Branches and foliage slow winds, reducing the threat of blowing sand covering up crops, and the trees increase infiltration and storage of rainfall. Some species even pull up water from far below ground using deep tap roots and spread water through the soil. And when trees come back, lizards, birds, and spiders return too, helping to fight insect pests.

Nevertheless, Reij and others are starting to change the narrative. “There’s now a growing movement around the world on landscape restoration,” says Paola Agostini, lead environmental economist in the Environment and Natural Resources Global Practice at the World Bank. The ramifications have included the first scaled-up projects funded by the Bank in countries like Ethiopia. In March 2019, the UN declared the start of a “Decade of Ecosystem Restoration” to encourage techniques like the natural regeneration in Niger (14, 15). And the Great Green Wall project has shifted to become a metaphor for such restoration, rather than a literal line of trees.

Christophersen also anticipates rapid growth in international finance for restoration projects, given the proven returns in increased agricultural productivity and in monetizing carbon capture and storage. He sees a parallel with renewable energy; few invested until the incentives and market forces changed sufficiently. “Financing the transformation of the landscape could be a new era for big development banks,” Christophersen says.