The “Great Green Wall” Didn’t Stop Desertification, but it Evolved Into Something That Might |Science | Smithsonian Magazine
https://www.smithsonianmag.com/...ature/great-green-wall-stop-desertification-not-so-much-180960171/
Slowly, the idea of a Great Green Wall has changed into a program centered around indigenous land use techniques, not planting a forest on the edge of a desert. The African Union and the United Nation's Food and Agriculture Organization now refer to it as "Africa’s flagship initiative to combat land degradation, desertification and drought." Incredibly, the Great Green Wall—or some form of it—appears to be working.
"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, the organization that examines the environmental benefit of World Bank projects. "It is not necessarily a physical wall, but rather a mosaic of land use practices that ultimately will meet the expectations of a wall. It has been transformed into a metaphorical thing."
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Over two years traveling through Burkina Faso and Niger, they uncovered a remarkable metamorphosis. Hundreds of thousands of farmers had embraced ingenious modifications of traditional agriculture practices, transforming large swaths into productive land, improving food and fuel production for about 3 million people.
"This regreening went on under our radar, everyone's radar, because we weren't using detailed enough satellite imagery. We were looking at general land use patterns, but we couldn't see the trees," Tappan says. "When we began to do aerial photography and field surveys, then we realized, boy, there is something very, very special going on here. These landscapes are really being transformed."
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Innovative farmers in Burkina Faso had adapted years earlier by necessity. They built zai, a grid of deep planting pits across rock-hard plots of land that enhanced water infiltration and retention during dry periods. They built stone barriers around fields to contain runoff and increase infiltration from rain.
In Niger, Reij and Tappan discovered what has become a central part of the new Great Green Wall campaign: farmer-managed natural regeneration, a middle ground between clearing the land and letting it go wild.
Farmers in the Sahel had learned from French colonists to clear land for agriculture and keep crops separate from trees. Under French colonial law and new laws that countries adopted after independence, any trees on a farmer's property belonged to the government. Farmers who cut down a tree for fuel would be threatened with jail. The idea was to preserve forests; it had the opposite effect.
"This was a terrific negative incentive to have a tree," Garrity says, during an interview from his Nairobi office. "For years and years, tree populations were declining."
But over decades without the shelter of trees, the topsoil dried up and blew away. Rainfall ran off instead of soaking into cropland. When Reij arrived in Africa, crop yields were less than 400 pounds per acre (compared to 5,600 pounds per acre in the United States) and water levels in wells were dropping by three feet per year.
In the early 1980s, as village populations increased and land productivity decreased, Reij says farmers turned to a low-cost way of growing trees and shrubs, using root stock in their cleared fields. The trees provided fuel, fodder for livestock, food, and soil improvement.
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Reij and Tappan discovered the regreening mostly stopped at the southern border with Nigeria, where there is more rainfall, which was counterintuitive, Tappan says. More precipitation should mean more vegetation. "It wasn't about rainfall," he adds. "It was absolutely about farmers changing the way they manage trees and their perception of the trees."
Tappan remembers giving a presentation to the U.S. Embassy in Niamey, Niger, showing aerial views of one green swath after another. "The comments were, 'this can't be Niger,'" he says. "It looks like Ireland."
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