As the Sahel dries, the Sahara advances

Here stands the Great Green Wall: Part 1

A 2011 satellite photo of the divide between the Sahara and the southern forests of Africa. NASA
23 October 2019
Natasha Vizcarra
23 October 2019
Natasha Vizcarra

The story is the first of a three-part Landscape News series on the Great Green Wall.

When Musonda Mumba saw the Niger River’s headwaters for the first time, it took her breath away. “In the middle of this incredibly arid space, there was this lifeline,” she says. “Even during the dry season, the river was full and flowing. For me, that was incredible.”

Mumba, a wetlands scientist and chief of the Terrestrial Ecosystems Unit at U.N. Environment, was in Mali to meet with colleagues working with the agency on rehabilitation of the Lake Faguibine system. “This lake is literally on the edge of the Sahara Desert,” she says. And at that time, it seemed the desert was slowly eating it alive.

Faguibine’s four interlinked lakes, located 600 kilometers northeast of Bamako, are connected to the Niger River and used to be the water source of one of Mali’s most fertile areas. Fishermen sold their catch along the sandy shores. Nomadic pastoralists herded goats, oxen, camels and sheep to graze on the savanna surrounding the lake. Farmers grew millet nearby.

Beginning in the 1970s, however, severe droughts lasting years dried the lake up. Sand from the Sahara filled the channels connected to the Niger River, preventing rainwater from reaching Faguibine during the wet season. Because of that, “the region’s prosperity evaporated along with the water,” U.N. Environment wrote in a report.

By the time U.N. Environment began working on the lake system’s revival in 2008, it hardly looked like it had ever held water. “It was so degraded and covered with sand,” says Mumba. But before the scientists and development workers could advance with the restoration work, armed conflicts broke out in Northern Mali.

“All hell broke loose,” says Mumba. “The region became insecure and unstable, so we’ve never gone back.”

Women collecting firewood for cooking pause on the cracked bed of the Niger River. United Nations Photo, Flickr
Women collecting firewood for cooking pause on the cracked bed of the Niger River. United Nations Photo, Flickr

The sand grows

The story of Lake Faguibine is one of many such narratives prevailing in the African continent’s Sahel region, a band of semi-arid land stretching from Senegal and Mauritiana on the western coast to parts of Sudan and Eritrea in the north-central region bordering the Red Sea.

The Sahelian belt is considered a region of transition between the Sahara Desert to the north and the tropical forests to the south. A tapestry of grasslands, savannas and shrublands, it gets most of its rain between June and September, varying across its latitude – annually, less than 200 millimeters in the north and more than 800 millimeters in the south.

However, parts of the Sahel have dried up in the past few decades; Lake Faguibine is only one example. Scientists attribute the desertification to long and severe droughts, particularly ones that occurred in the 1970s and ‘80s, and human activities such as unsustainable farming practices and overgrazing, with animals removing most of the vegetation in some areas, leaving the soil exposed to heat and vulnerable to erosion.

Soil compaction has also been a problem. “Think of the hooves of these animals and how they trample the soil,” says Mumba. “When they compact the soil, seeds buried in it can no longer germinate. And when it rains, the water does not seep into the soil. It just washes over, taking the topsoil with it.”

Erratic rainfall patterns and a warming climate have compounded issues for the Sahel’s ecological health. “The ecosystem is under such pressure from so many sides that it’s on the edge,” says Mumba. “It’s at a tipping point where its recovery is at stake.”

And Mali is not the only part of the Sahel that has been experiencing armed conflict, forcing people to migrate to safer places, where often they are unwelcome socially – let alone to settle on the land and plant crops.

Children wave from the river bank in Burkina Faso. Daniel Tiveau, CIFOR

A tipping point

The dominoes have been falling. Climate change affects the land, and conflict does not give it a chance to recover. Aridity comes in, and with less water circulating between the land and atmosphere, rainfall patterns then change.

“And because the winds of the Sahara are strong, it covers up and occupies the land,” says Mumba. “Where you once had shrubs and grass, down the line it’s a sand dune.”

Scientists have documented changes in the Sahara’s extent that hint at an increase in desertification. A 1991 study says the Saharan-Sahelian boundary has progressively moved southward at about 60 kilometers per year from 1980 to 1984. A more recent study says the Sahara desert has grown in size by 10 percent from 1902 to 2013.

What this means in the bigger picture is that as the Sahel dries, the Sahara Desert advances southward into it. And as this happens, the southern edge of the Sahel creeps down into the region of the humid forests.

This degradation, the armed skirmishes in some countries, and the expected population growth in the Sahel portend a looming humanitarian crisis. The Sahel supports around 135 million people today. By 2050, this population is expected to more than double, to the tune of 330 million. And by 2100 the region will need to support 670 million people.

“We need to do something now,” says Mumba. “If we don’t, we’re going to find that there is just no other space to move to.”

Agricultural landscapes, such as this one of maize, cabbage, lettuce, potatoes, and beans, are now being incorporated into the planning of the Great Green Wall. Ollivier Girard, CIFOR

The Great Green Wall

In 2007, the African Union created the Great Green Wall (GGW) for the Sahara and the Sahel initiative, an ambitious program to plant a wall of trees stretching 15 kilometers wide and 7,775 kilometers long within the Sahelian belt. Eleven countries – Burkina Faso, Chad, Djibouti, Eritrea, Ethiopia, Mali, Mauritania, Niger, Nigeria, Senegal, and Sudan – signed up for the program.

The grand vision for such a wall has now endured more than three decades since it was first conceived by Thomas Sankara, Burkina Faso’s president in the mid-1980s, and more than 15 years since Nigerian president Olusegun Obasanjo successfully turned it to a formal African initiative during a summit of Sahel and Saharan states in 2005.

“They wanted a framework that was coherent and consistent across the entire geography, so they could pursue an agenda that was aligned with their national interests, the realities of their countries and also the development opportunities that were associated with land use and land management across the region,” says Mohamed Bakarr, senior environmental specialist with the Global Environment Facility (GEF). The organization provided Great Green Wall countries grants totaling USD 108 million to kickstart their restoration projects.

After several years, organizers modified the initial “wall of trees” strategy to a mosaic of forests and diverse vegetation using traditional restoration techniques from the Sahel’s various communities. Various donors gave and pledged up to USD 8 billion to the program and some 10 more countries joined the initiative.

Against many odds, some projects seem to be working. But will they be enough? And how will these play out in a future of higher temperatures and a skyrocketing population?

Next: Why trees could bring back water to the Sahel


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