The Sahel is the strip of land that separates the Sahara and the African savannahs, but it is increasingly more desert than anything else. The United Nations UNCCD has already warned that the Sahel is one of the regions of Africa most vulnerable to desertification and what it entails: soils so hardened that they prevent water penetration and plants no longer take root. If planting is not possible and conditions become harsh, desertification leads to forced migration of those who live there.
The classic response to try to stop desertification has been to plant trees, but it is an expensive method and does not always work, so someone has proposed a different experiment: it is not introducing vegetation but rather returning an animal whose behavior is capable of changing the structure of the soil.
Turtles for frenew the desert. In 2021 a research team he blurted out 500 african spurred tortoises precisely on the southern border of the Sahara. They didn’t do anything special, just let them do their thing. Five years later, satellite images they have confirmed that where before there was only sand, now there are green patches of vegetation.
And what do African turtles do? Well dig. This species, whose natural habitat is precisely the Sahelbuilds burrows up to 15 meters in length to instinctively protect themselves from heat and cold. This construction work breaks up the crust of the soil, allowing water to pass through and ultimately creating more favorable conditions for seeds to germinate.
Why is it important. Because the African spurred tortoise is a ecosystem engineer: a species that benefits other species with its modification of the environment. Like the UNCCD has already pointed outland restoration is one of the best solutions to desertification and the turtle does it alone, without the need for machinery. For local communities, digging in semi-desert areas to have holes that retain water is an arduous task that the turtle does natively throughout its life.
Paradoxically, the African spurred tortoise is native there, but it is increasingly difficult to find because it is threatened. That this turtle disappears from the Sahel is bad news for biodiversity, but also for the soil: without its valuable excavation work, the surface hardens, the water drains away and, ultimately, the seeds do not hold.
Context. The soil of the Sahel has been so degraded in recent decades that as early as 1977 was organized in NairobiKenya, the first United Nations Conference on Desertification. Although it is one of the most vulnerable areas, it is one of the great structural problems of Africa: two thirds of the continent is classified as deserts or arid lands and it is estimated that two thirds of African land is already degraded to some degree.
But for the African spurred tortoise it has not been a bed of roses either: it has been under the magnifying glass of the Convention on International Trade in Endangered Species of Wild Fauna and Flora since 2000, with restrictions to protect it and reintroduction in the north and west of Ferlo and Senegal: in 2017 the African Chelonian Institute already made a documented release of 20 individuals. There are also captive colonies in several countries in Africa and outside of it. However, the according to the IUCN Red List The species’ population continues to decline due to habitat loss, exploitation for eggs and meat, the pet trade, and the effects of climate change such as desertification.
In detail. The ecological mechanism consists in which the turtle’s digging breaks up the hardened crust of the soil and its tunnels allow rainwater to penetrate deeper layers, instead of evaporating quickly. As a result, porosity improves, surface temperature decreases and nutrient availability is enhanced.
As a consequence, the soil gains water retention capacity and humidity is maintained longer. Seeds that could not germinate before find the minimum conditions to develop. In addition, insects and microorganisms colonize these excavated spaces, which activates the ecological chain and ends up attracting birds and small vertebrates. It is not a lush jungle, but it has enough green shoots to stop desertification and recover biodiversity.
Yes, but. The reintroduction of turtles does not work miracles: it is just the starting point. For the process to progress on the right track, other requirements are necessary, such as availability of rain and a sustainable and stable management policy. There is little point in introducing them if they are later hunted, something not unreasonable given that the species is already threatened. On the other hand, we know that digging improves the soil, but I could be doing something else: disperse seeds throughout the Sahel, so that part of those new green shoots are also their work without us yet knowing it.
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