A line of trees to stop the Sahara

Deserts, as you will know, are mobile creatures. They are not content to sit in one place, but creep about, enlarging themselves at the edges. Over the decades and centuries, a desert can eat a whole country.

The Sahara has already swallowed North Africa, and is moving slowly south. It has found a major ally in climate change, which is reducing rainfall over the land it wishes to conquer. If the countries currently designated as Sub-Saharan wish to keep that description, there is work to do.

There have been plenty of ambitious schemes hatched to push back or reforest the Sahara. Many of them are closer to science fiction than they are to Africa as we know it, but the Great Green Wall is an exception. It has won the backing of the African Union, attracted funding from a wide variety of sources, and is now underway.

As the name suggests, the Great Green Wall project aims to plant a forest to hold back the Sahara. It will reach right across the continent from Senegal to Djibouti, 15 km wide and spanning 11 countries. Senegal has already started planting.

It’s easy to imagine a literal belt of trees, but the project is a little more complex than that. It will be a mix of agricultural and forest areas, each tailored to the needs of the local community so that the trees can contribute to food security, poverty alleviation and biodiversity as well as stopping desertification. It will also be a carbon sink, which may explain why an idea that has been around since the 80s is finally getting funding – there’s money to be made in carbon credits at the moment.

The Green Wall won’t be cheap and it won’t happen fast, and some suggest it’s a waste of time in the first place because it won’t work. Applied haphazardly and with varying degrees of competence across its 4,500 mile length, it may make things worse in some places. Local communities could be displaced. Non-native trees might not survive the dry seasons, drawing up water from smaller plants only to die anyway. And can a line of trees actually stop an encroaching desert?

There is precedent. Israel has successfully replanted parts of the Negev, using irrigation techniques that store and channel water. Niger has proved you can re-green with no new technology or big coordinated programmes, and Kenya’s Green Belt Movement shows what grassroots tree-planting can achieve. China has had a more mixed experience. The country leveled its forests in the ‘Great Leap Forward’, probably the most explicit and deliberate ‘war on nature’ ever attempted. Mending the damage has become a major national project. Many reforestation schemes are successful and total forest coverage is increasing in China. But, China’s own ‘Great Green Wall’ to hold back the Gobi desert is struggling, over-reliant on fast-growing non-native species that are lowering groundwater levels and dying in large numbers.

It’s clear that reforestation can work, done well. The Sahel’s Green Wall is also symbolic, a rare incidence of countries cooperating to attempt an ambitious environmental programme. If it succeeds, it will be an icon of the fightback against climate change.

Perhaps because of its symbolic nature, the project is drawing attention from funding bodies, NGOs and entrepreneurs. Foresters have experimented with the remarkable Moringa tree, an edible and medicinal tree that is also very hardy and drought resistant.  Traditional techniques are being exchanged, like the ‘diguettes’ used in Burkina Faso – mini dry-stone walls that stabilise the soil and prevent run-off when it rains. The challenge has caught the imagination of engineers and inventors, like Pieter Hoff and his waterboxx for growing plants and trees with 80% less water. It’ll take decades, but if the energy can be sustained and best practice shared, maybe sub-Saharan Africa can stay that way.