The planting of an 8,000km ‘wall’ of trees is underway in Africa. If
completed it will be three times the size of the Great Barrier Reef and
the world’s largest living structure.
The aim is help fight desertification and land degradation and to
restore native plants in the ‘drylands’ of Africa. New fertile areas
will provide sustainable livelihoods for local people, particularly in
the the worst hit drought-prone areas such as the Sahel region on the
edge of the Sahara where poor land management (over farming; over
grazing) and a lack of arable land has led to food and water security
concerns for the booming population.
The Sahel receive only 4-24 inches of water in a year and climate
change is expected to further impact this region. An estimated 500
million people live on land undergoing desertification.
If people can’t provide for their families, the practice of
‘transhumance’ (migrating from one area to another with livestock in a
seasonal cycle) may become more widespread.
Protecting and restoring
The initial vision for the $8-billion Great Green Wall, a project
launched in 2007, was to span Africa from west to east restoring 100
million hectares of degraded land by 2030. This 15km wide buffer of new
trees would generate thousands of rural jobs and create a vast carbon
sink – it is estimated the trees would absorb c 250 million tons of CO2 from the atmosphere.
This process of using natural resources (as opposed to man-made
structures) to ward against the impact of climate change is called ecosystem-based adaption : trees,
wetlands, lakes and streams are natural water stores; the foilage of
trees can provide deep, cooling shade; mangroves work as coastal
defences and the roots of vegetation protect against soil erosion.
However, it’s not simple to plant a forest on the edge of a shifting desert!
Rather than a band of trees stretching the width of the continent,
Africa’s Great Green Wall is more a wide belt of vegetation surrounding
pockets of farmland along the margins of the Sahara. These ‘shelter
belts’ (lines of trees & shrubs) protect areas, including precious
crops, from extreme weather events.
The green mosaic varies from country to country depending on
traditional farming techniques and the individual goals of any given
nation, for example, to diversify crops, slow soil erosion or improve
For example in Senegal local farmers are allocated land parcels and
are encouraged to regenerate native vegetation on the land – this
includes acacia species Senegalia senegal, which has economic value through the production of gum arabic which is widely used as a food additive. It is their responsibility to dig irrigation
canals and plant drought-tolerant species. Results have already been
seen and the relationship with the landscape has subtly changed. Lush
oases of banana, cassava, okra, lemon, mint and mango have been
springing up amidst these natural vegetation shelter belts. Rather than
adopting intensive farming techniques and clearing land, children
learn to nurture the vegetation that’s already there, creating these
green zones and helping to retain ground water and create
shade/protection for their crops.
In turn, the vegetation provides habitat for endangered species and helps to safeguard biodiversity.
15% of the wall is now complete with 21 countries involved. Statistics below from the United Nations Convention to Combat Desertification:
Ethiopia: 15 million hectares of degraded land restored, land tenure security improved
Senegal: 11.4 million trees planted, 25 000 hectares of degraded land restored
Nigeria: 5 million hectares of degraded land restored and 20 000 jobs created
Sudan: 2,000 hectares of land restored
Burkina Faso, Mali, Niger:
About 120 communities involved, a green belt created over more than
2,500 hectares of degraded and drylands, more than two million seeds and
seedlings planted from fifty native species of trees