Old people in Widou Thiengoly say they can remember when there were so many trees that you couldn’t see the sky.Now, miles of reddish-brown sand surround this village in northwestern Senegal, dotted with occasional bushes and trees. Dried animal dung is scattered everywhere, but hardly any dried grass is.
Overgrazing and climate change are the major causes of the Sahara’s advance, said Gilles Boetsch, an anthropologist who directs a team of French scientists working with Senegalese researchers in the region.“The local Peul people are herders, often nomadic. But the pressure of the herds on the land has become too great,” Mr. Boetsch said in an interview. “The vegetation can’t regenerate itself.”
Since 2008, however, Senegal has been fighting back against the encroaching desert. Each year it has planted some two million seedling trees along a 545-kilometer, or 340-mile, ribbon of land that is the country’s segment of a major pan-African regeneration project, the Great Green Wall.First proposed in 2005, the program links Senegal and 10 other Saharan states in an alliance to plant a 15 kilometer-wide, 7,100-kilometer-long green belt to fend off the desert.While many countries have still to start on their sections of the barrier, Senegal has taken the lead, with the creation of a National Agency for the Great Green Wall.
“This semi-arid region is becoming less and less habitable. We want to make it possible for people to continue to live here,” Col. Pap Sarr, the agency’s technical director, said in an interview here. Colonel Sarr has forged working alliances between Senegalese researchers and the French team headed by Mr. Boetsch, in fields as varied as soil microbiology, ecology, medicine and anthropology.“In Senegal we hope to experiment with different ways of doing things that will benefit the other countries as they become more active,” the colonel said.Each year since 2008, from May to June, about 400 people are employed in eight nurseries, choosing and overseeing germination of seeds and tending the seedlings until they are ready for planting. In August, 1,000 people are mobilized to plant out rows of seedlings, about 2 million plants, allowing them a full two months of the rainy season to take root before the long, dry season sets in.
After their first dry season, the saplings look dead, brown twigs sticking out of holes in the ground, but 80 percent survive. Six years on, trees planted in 2008 are up to three meters, or 10 feet, tall.So far, 30,000 hectares, or about 75,000 acres, have been planted, including 4,000 hectares this summer.There are already discernible impacts on the microclimate, said Jean-Luc Peiry, a physical geography professor at the Université Blaise Pascal in Clermont-Ferrand, France, who has placed 30 sensors to record temperatures in some planted parcels.
“Preliminary results show that clumps of four to eight small trees can have an important impact on temperature,” Professor Peiry said in an interview. “The transpiration of the trees creates a microclimate that moderates daily temperature extremes.”“The trees also have an important role in slowing the soil erosion caused by the wind, reducing the dust, and acting like a large rough doormat, halting the sand-laden winds from the Sahara,” he added.Wildlife is responding to the changes. “Migratory birds are reappearing,” Mr. Boetsch said.
The project uses eight groundwater pumping stations built in 1954, before Senegal achieved its independence from France in 1960. The pumps fill giant basins that provide water for animals, tree nurseries and gardens where fruit and vegetables are grown.