A “green wall” is intended to protect the landscape of the Sahel zone from further barriers and degradation. For this purpose, new trees, grasses or domestic crops are to be planted on 100 million hectares. A research team has now examined in more detail whether this investment is worthwhile and which renaturation measures would be useful where. Their result: almost everywhere, the economic advantages would outweigh the costs.
The Sahel zone on the southern edge of the Sahara extends from Senegal in the west to Ethiopia in the east of Africa. Once a fertile region, the Sahel zone is today barren, dry and, in large parts, almost free of vegetation. Reasons include droughts, the felling of trees for firewood, as well as overexploitation due to cattle grazing and unsuitable agricultural cultivation methods. As a result, many people in this region are struggling to survive because they threaten to lose their livelihood.
To counteract this, the African Union decided on an ambitious project in 2017: The largely degraded habitats of the Sahel zone should be gradually renatured on around 100 million hectares – for example by planting native trees, bushes and grasses as well as sustainable forms of the Crop cultivation. This “green wall” is intended to protect the soils of the Sahel zone from further degradation, stop the desert from advancing and help the people in this area to secure their food. The re-greening of the barren Sahel also helps to bind the greenhouse gas carbon dioxide and thus counteracts climate change.
Where and how is the Green Wall meaningful and worthwhile?
So far, however, the “Green Wall” initiative has only been implemented on around four of the planned 100 million hectares – also because there is a lack of financial resources. But that will change: at the beginning of 2021, various donor countries pledged almost 15 billion US dollars for the project at the “One Planet” summit for biodiversity. “In order to use these funds efficiently, we now have to ask ourselves where and for which measures they should be used most sensibly,” says Alisher Mirzabaev from the Center for Development Research (ZEF) at the University of Bonn. This is exactly what he and his colleagues have now investigated in more detail. To do this, they divided the Sahel zone into 40 million parcels of 25 hectares each and analyzed for each which renaturation measures would be possible there and how much they would cost.
In nine scenarios, the researchers then examined what benefits the various measures would look like in the areas covered. “On the one hand, this includes the so-called provisioning services,” explains Mirzabaev. “These are the things that are generated by the ecosystem: food and drinking water, raw materials such as wood or medicinal plants.” There are also other advantages such as a better climate, less wind erosion or the fact that pollinators settle on the green areas, which in turn increase farmers’ crop yields. You can also attach a price tag to them today.
Advantages almost always outweigh
The results show that building the “Green Wall” is economically worthwhile. Because in almost all areas the benefits gained by investing in land improvement are significantly higher than the costs resulting from the ongoing degradation of the landscape. “The costs of land degradation in the Sahel region are estimated at around three billion US dollars annually for the period from 2001 to 2018,” the researchers report. “At the same time, the annual profits from renaturation amounted to around 4.2 billion US dollars.” Overall, the scientists estimate that between 18 and 70 billion US dollars would be required for the renaturation measures on the Green Wall. But for every dollar invested, you would end up with a plus in almost all countries and areas of the Sahel zone.
How great the economic advantages of the initiative are, however, depends on the land, the ownership structure of the land and the way of life and situation of the population. So it would be economically and ecologically mostly a reforestation most advantageous. But it will take around 30 years for a few hundred seedlings to grow into a forest. For the population, this means that they only benefit from the advantages of the improved land quality at a late stage. If, on the other hand, degraded areas are converted into sustainably used arable land, this pays for itself comparatively quickly – which would benefit areas with many poor smallholders in particular. “Ideally, the first serious one is possible after just one year,” says Mirzabaev.
Big regional differences
As a result of this and the local conditions, among other things, there are strong regional fluctuations in the relationship between costs and benefits. The economic balance is most positive for parts of Nigeria, Eritrea and Ethiopia. Here you would get back an average of 1.60 to 2.40 dollars for every US dollar invested in land improvement. In Nigeria, which is characterized by severe deforestation, afforestation could even bring net profits of up to US $ 5.50, as the team has calculated. An investment in the “Green Wall” would therefore have a particularly large number of positive effects in these countries, also from an economic point of view.
The analysis also shows, however, that the ambitious initiative will probably hardly be feasible in some parts of the Sahel zone. Because of armed conflicts, many of the regions in which the construction of the Green Wall would make sense are simply too unsafe for such measures. “If we factor out these areas, there are just 14 million hectares left,” says Mirzabaev. “This shows how much such disputes not only cause direct human suffering, but also prevent positive development in the affected regions.”
Source: University of Bonn; Technical article: Nature Sustainability, doi: 10.1038 / s41893-021-00801-8