Leaves serve other purposes. After they fall to the ground, they act as mulch, boosting soil fertility; they also provide fodder for livestock in a season when little other food is available. In emergencies, people too can eat the leaves to avoid starvation.
The improved planting pits developed by Sawadogo and other simple water-harvesting techniques have enabled more water to infiltrate the soil. Amazingly, underground water tables that plummeted after the droughts of the 1980s had now begun recharging. "In the 1980s, water tables on the Central Plateau of Burkina Faso were falling by an average of one meter a year," Reij said. "Since FMNR and the water-harvesting techniques began to take hold in the late 1980s, water tables in many villages have risen by at least five meters, despite a growing population."
Some analysts attributed the rise in water tables to an increase in rainfall that occurred beginning in 1994, Reij added, "but that doesn't make sense—the water tables began rising well before that." Studies have documented the same phenomenon in some villages in Niger, where extensive water-harvesting measures helped raise water tables by fifteen meters between the early 1990s and 2005.
Over time, Sawadogo grew more and more enamored of trees, until now his land looked less like a farm than a forest, albeit a forest composed of trees that, to my California eyes, often looked rather thin and patchy. Trees can be harvested—their branches pruned and sold—and then they grow back, and their benefits for the soil make it easier for additional trees to grow. "The more trees you have, the more you get," Sawadogo explained. Wood is the main energy source in rural Africa, and as his tree cover expanded, Sawadogo sold wood for cooking, furniture making, and construction, thus increasing and diversifying his income—a key adaptation tactic. Trees, he says, are also a source of natural medicines, no small advantage in an area where modern health care is scarce and expensive.
"I think trees are at least a partial answer to climate change, and I've tried to share this information with others," Sawadogo added. "My conviction, based on personal experience, is that trees are like lungs. If we do not protect them, and increase their numbers, it will be the end of the world."
The largest environmental transformation in Africa
Sawadogo was not an anomaly. In Mali, the practice of growing trees amid rows of cropland seemed to be everywhere. A bone-jarring three hour drive from the Burkina Faso border brought us to the village of Sokoura. By global standards, Sokoura was very poor. Houses were made of sticks covered by mud. There was no electricity or running water.
Children wore dirty, torn clothes, and more than a few were naked, their distended bellies hinting at insufficient diets. When one of our team let an empty plastic bottle fall to the ground, kids wrestled for it as if it were gold. Yet to hear locals tell it, life was improving in Sokoura.
It was a five-minute walk from the village to the land of Omar Guindo. Missing a front tooth and wearing a black smock over green slacks, Guindo said that ten years ago he began taking advice from Sahel Eco, a Malian NGO that promotes agro-forestry. Now, Guindo's land was dotted with trees, one every five meters or so. Most were young, with such spindly branches that they resembled bushes more than trees, but there were also a few specimens with trunks the width of fire hydrants. We sat beneath a large tree known as the "Apple of the Sahel," whose twigs sported inch-long thorns. The soil was sandy in both color and consistency—not a farmer's ideal—but water availability and crop yields had increased substantially. "Before, this fi eld couldn't fill even one granary," he said. "Now, it fills one granary and half of another"—roughly a 50 percent increase in production.