They released 500 tortoises to halt the Sahara’s advance in 2021: here’s what happened
Here’s what happened when 500 tortoises were released into the Sahara’s in 2021.
In the Sahel, daytime temperatures can reach 60°C, while at night the air cools sharply. On this hardened ground, rainwater is unable to penetrate the soil. Moisture evaporates almost immediately, and seeds cannot germinate.
For that reason, researchers released 500 African tortoises into a barren landscape south of the Sahara. The animals belong to the species Centrochelys sulcata, which evolved to survive precisely these conditions. Five years later, images showed green patches appearing across the area.
The African spurred tortoise is the largest mainland tortoise in the world and the third largest tortoise overall, after the Galápagos and Aldabra tortoises. Males can weigh more than 100 kg. Beyond its impressive size, the species is remarkable for its digging ability.
To escape the extreme heat, it excavates burrows 10 to 15 metres deep, where it can shelter from both the intense daytime temperatures and the cold nights. These burrows also help aerate the soil.
When the burrows break through the hardened surface, rainwater can infiltrate the ground instead of running off. This improves the soil’s capacity to retain moisture, allowing it to remain damp for longer after rainfall.
This effect has already been documented in Senegal. The organisation S.O.S. (Save Our Sulcata) has operated breeding and reintroduction programmes since 1992. A 2020 IUCN report mentions the Village des Tortues sanctuary in Noflaye, which houses more than 300 tortoises and has released several animals into their natural habitat.
The process is primarily physical: the entrance to the burrow and the excavated soil create a more stable microclimate. Although tortoises do not deliberately disperse seeds, seeds already present in the soil or carried by the wind can germinate thanks to the increased moisture and protection around the burrow.
The burrows also attract insects and microorganisms, benefiting soil life. Over time, vegetation becomes denser around these sites, forming green patches that are visible even in satellite imagery and are associated with the tortoises’ digging activity.
The release of around 500 tortoises in 2021 was significant, although IUCN data indicate that the reintroduction programme in Senegal has been running for decades. In monitored groups, survival rates of more than 80% have been recorded over several years, a crucial factor in maintaining both their digging activity and their impact on the landscape.
No reforestation techniques or soil treatments were used. The intervention consisted simply of reintroducing a native species whose numbers had declined because of hunting, agriculture, and grazing. Over time, previously barren areas began to regain vegetation and attract wildlife such as birds and small vertebrates, leading to greater biodiversity.
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