IT IS terraforming on a grand scale. A sinuous line of trees has started to spring up across the hottest, driest and widest part of Africa. Once finished, the band of green against gold will stretch from the Atlantic coast of Senegal, across the southern fringe of the Sahara desert to the Red Sea 鈥� and be visible from space.
The purpose of this ? To hold back the advancing sands of the Sahara in the name of fighting climate change.
Formally inaugurated in May, it is a grand project of the African Union (AU), with 11 nations signed up. Senegal has taken the lead and last year its president Macky Sall announced that it had already planted 12 million trees, mostly native acacias. The final wall, set to be 15 kilometres wide and almost 8000 kilometres long, will number more than a billion trees.
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And yet questions abound. Will it work? What part of the 鈥渄esertification鈥� process is it intended to prevent? Is advancing sand the real problem? Come to that, what鈥檚 wrong with deserts anyway? Maybe we should be saving deserts 鈥� and their unique flora and fauna 鈥� rather than fighting them.
Some $4 billion has so far been promised for the project, which is being masterminded by forest scientists working for the AU. The World Bank, the European Union and private investors are all piling in.
鈥淭he final wall will be 15 kilometres wide and 8000 kilometres long, with more than a billion trees鈥�
The wall鈥檚 backers say it will halt the desert鈥檚 advances, cool the air with its shade, block sand storms, provide shelter for livestock, fertilise soils and protect water supplies. By bringing rural prosperity, it could also counter the rise of Islamic militants such as Boko Haram. Abdou Maisharou, director of Niger鈥檚 National Great Green Wall Agency, has said it would 鈥渄eter young people from leaving their lands [and so] combat terrorism鈥�.
Wildlife could also benefit. Elvis Paul Tangem, who coordinates the project for the AU, claimed recently that antelope, hares and birds are returning to newly forested areas in Senegal after a 50 year absence.
The Great Green Wall has strong echoes of China鈥檚 recent efforts to create its own belt of an estimated 100 billion trees, a project that shows some signs of improving vegetation and reducing dust storms.
But few desert specialists believe it will work in the Sahara. 鈥淭echnically it makes no sense,鈥� says Chris Reij of the World Resources Institute, a US think tank. 鈥淲e don鈥檛 need a Great Green Wall. It solves nothing. We need green landscapes instead.鈥�
Part of the problem is that many believe the diagnosis is wrong. The science behind an advancing Sahara is hotly contested: many researchers say the whole idea 鈥� which has been a given of environmental debate since the 1970s 鈥� is a myth.
Wrong diagnosis
鈥淟ocalised, even severe, land degradation certainly exists in the region,鈥� says UK-based geographer Mike Mortimore, who recently co-authored the book The End of Desertification? It may result from changing climatic conditions, overgrazing, clearing vegetation for farming, or dams and water diversions that deprive low-lying areas along rivers of their natural floods.
But these short-term local changes, usually assessed from aerial surveys, are being misread as part of a widespread, long-term trend, he says. 鈥淭here is no evidence of a catastrophic regional environmental crisis.鈥�
In reality, deserts advance and retreat regularly, often as a result of routine climatic variability. During droughts in the 1970s and 80s, the Sahara did in some places move south. At the time livestock herders were blamed for creating irreversible advances by overgrazing their animals on the fringes of the Sahara. But since the 1990s, the desert has retreated in many places, often as rains have improved.
Mortimore says it is wrong to blame overgrazing, as the UN Environment Programme, which once demonised the practice, now says . Instead, poor water management is behind the continued spread of deserts in some regions, says Jane Madgwick, director of the Dutch-based NGO Wetlands International 鈥� and the Great Green Wall isn鈥檛 the cure.
Take Lake Chad, on the border between Niger, Nigeria, Chad and Cameroon, which is only a tenth the size it was a few decades ago. The wall is planned to pass through the heart of the huge basin of rivers that drain into the lake. But irrigation dams, not deserts, are to blame for its decline, says Madgwick. They have , she says. Planting trees won鈥檛 reverse the lake鈥檚 fortunes.
In any case, the idea of seeing deserts as an ecological disease to be fought is foolhardy. Deserts are natural ecosystems, home to numerous species that have made it their own, many of which are endangered. Traditional nomadic societies found ways to live in such environments, through hunting and herding animals. Modern farming methods fail without massive imports of irrigation water, which may create new deserts elsewhere.
Reij points to farmers across the region who have found their own way of reviving their arid lands, often by abandoning the advice given to them by governments to cut down native trees and nurturing them instead (see 鈥�View from the ground鈥�).
The results have been spectacular, says Reij. His research shows that trees growing amid crops retain water on the land, improve soils through dropping leaf litter and stave off drought.
The practice is spreading, from Niger to Mali, Burkina Faso and beyond. Certainly far more trees have emerged in the landscape thanks to these farmers than from the Great Green Wall.
鈥淲e don鈥檛 need a Great Green Wall. It solves nothing. We need green landscapes instead鈥�
The wall project is already working with local people. Moctar Sacande, a forest ecologist at London鈥檚 Royal Botanic Gardens in Kew, is masterminding a programme in Mali, Burkina Faso and Niger as part of the Great Green Wall to consult villagers about native seeds for use in growing the wall. They will collect the seeds locally, propagate them in nurseries and pay villagers to plant them. 鈥淲e start by consulting communities,鈥� he says.
But Reij and others believe the farmer-led approach of encouraging existing trees could be the basis for the recovery of ecosystems around the Sahara that would benefit farmers, cattle herders and wildlife alike.
Perhaps, suggests Reij, the strategy of the Great Green Wall could be changed to follow the farmers鈥� lead. The ultimate irony would be for a green landscape to emerge without a single further tree being planted.
View from the ground
鈥淎 decade ago this land was dismissed as lost to the desert,鈥� says ecologist Mamadou Diakite. But now he is smiling beneath the shade of a tree, one of hundreds growing vigorously around us on what was once parched land, abandoned by local millet farmers in a remote region of Mali near the ancient city of Djenn茅.
Though the Mali government supports the Great Green Wall project (see main story), these trees aren鈥檛 the result of an official planting programme. Instead, local farmers have been encouraging the growth of trees on land at the edge of the desert. Rather than following long-standing advice from government agricultural advisers to uproot trees on their fields and chop out any new growth, they have nurtured them instead.
Bringing it back
Begun in neighbouring Niger more than a decade ago, the practice, dubbed Farmer-Managed Natural Regeneration, is now spreading. It has been supported by NGOs such as Diakite鈥檚 Mali-based organisation, Sahel Eco.
鈥淚t was slow to take off, but now they all want to do it,鈥� he says. 鈥淭he land is coming back into production. Farmers use the wood for firewood and the leaves provide fodder for their animals and fertilise the soils.鈥�
This article appeared in print under the headline 鈥淕reen and desert land鈥�
