On the slopes of northern Tanzania, extensive trenches slice through fields that once grew maize, beans, vegetables, etc. In some villages, these gullies are wide enough to swallow footpaths, fences and sections of road. Farmers and pastoralists who depend on the land, see that the soil erosion is no longer an abstract environmental concern, than a daily threat to food, income and sociosecurity.
Gully erosion happens when flowing rainwater cuts rapidly into the ground and it is spreading across large parts of the Tanzanian highlands. What was once a slow natural process, has accelerated into a crisis with human, economic and political consequences. Researchers now warn that soil loss is undermining national development goals, pushing already vulnerable communities closer to hunger/displacement, driving a transit from environmental process to humanitarian risk.
Erosion happens everywhere. Rain breaks soil into particles, which are then carried downhill into rivers and lakes. But in Tanzania, erosion rates have increased dramatically over the past century. Scientists estimated that soil is being lost around 20 times faster than it was 120 years ago, and more than half of the country’s land area shows signs of rapid degradation. The reasons are partly natural.
Northern Tanzania’s steep landscapes, erratic rainfall and fragile volcanic soils make the region inherently vulnerable. These soils that formed from ancient basalt as the East African Rift opened, are rich but unstable. After long dry periods, intense rain can cause them to disperse into fine particles that wash away easily. Moreso, the way lands are now used, has turned vulnerability into crisis.
Clearing forests and savannahs for farming, combined with rising livestock numbers, has stripped soils of the vegetation and roots that was holding them together. When heavy rain arrives, water rushes downslope concentrating in valleys and tearing open gullies that grow larger each season. A farmer near Arusha told researchers that “these are not just cracks in the earth. They are eating our farms”.
Indigenous land management systems once reduced these risks. Seasonal grazing, fallowing/shifting cultivation allowed vegetation to recover, while soils rebuild. But these practices were steadily diluted during colonial rule and after independence, as policies favoured permanent settlement, fixed land boundaries and continuous cultivation.
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