Why is Soil Erosion Such a Big Problem in East Africa?

When rain falls heavily on the land, the raindrops break the soil into small pieces. Rushing water can also break off large chunks of soil. The flowing water then carries these pieces downhill, into rivers and lakes. This process is called soil erosion. Erosion is natural, but human activity has increased the speed of this process. Nowhere in the world is this problem so urgent as in East Africa.

East Africa has unpredictable, heavy rains and many steep hills. The best farmlands are found on the volcanic highlands, where the soil is good for growing crops and rain falls more often. Volcanic basalts, the rocks that formed from cooled lava from eruptions, slowly break down into very fertile volcanic soils. These soils are rich in clay, nutrients, and minerals like sodium and calcium, which make them great for plants but also very fragile. When water touches these soils, the tiny soil clumps can suddenly break apart, almost like they are “exploding” into much smaller pieces. These particles are so small that water can easily carry them away. Some soil particles are washed downhill, while others settle back on the soil surface and form a thin, hard layer called a soil crust. This crust acts like a lid, stopping rainwater from soaking into the ground. Instead, more water flows quickly downhill, which can cause even more erosion. Luckily, the natural trees and grasses that grow on these soils protect them from the rain.

How People Made the Problem Worse

Soil erosion was not always such a big problem, but East Africa’s population is growing fast—doubling about every 25 years! Most East African people depend on farming or animal keeping for their food and income. Farmers clear all plants from their fields before the rain starts, leaving the soil bare and easy to wash away. More farmland and bigger herds of animals mean fewer natural plants and trees to protect the soil. We have measured that, because of these changes, erosion has increased by almost 20 times in the last 100 years [1]!

During regime shifts, the landscape quickly changed in a big and long-lasting way (Figure 1). You can imagine this like a boulder on a mountain. It takes a strong push to get it moving, but once it starts, it rolls down quickly, destroying everything in its path. The first push came at the end of the colonial period when forests were cut down for farms. The farms were not managed sustainably and quickly started losing their soil. The second push happened when governments forced nomadic herders to stay in one place with their animals instead of following the rains. This resulted in the grasslands becoming overgrazed, and plants no longer had time to grow back.

Without trees and grasses, rainwater runs down the hills faster instead of soaking into the ground. At the places in the landscape where fast-flowing water comes together, big gullies started to form, which are steep, deep cuts in the landscape. These gullies grow bigger, deeper, and faster every year (Figure 2). They quickly carry soil and nutrients away from the land. Every year, more and more land is lost to soil erosion [2]. Not only land is lost, gullies can even destroy roads, houses, schools, and bridges. This makes it harder for kids to attend school and for people to buy and sell goods in markets. The eroded soil ends up in lakes and reservoirs, filling them up and destroying nature and sources of clean water.

Finding the Root of the Problem

Stopping erosion is hard, just like stopping a rolling boulder. Gullies can form later and far away from where the problem started. If one part of the land changes, it can affect places far away. For example, cutting down trees to make farms on a hill can cause floods and gullies in the valleys below. Once gullies exist, they often keep growing even if the original problem has stopped, making it hard for plants to grow back and the land to restore. Animals lose their food sources, rivers get dirty, and people lose their farms and clean water.

Over half of East Africans are under age 18, growing up on land that is already damaged. They face a big challenge: how to restore the land while also finding jobs and supporting their futures. Stopping soil erosion is not as simple as fixing a farm or planting a few trees here and there. It needs a whole-system approach, which means that everything is connected [3]. So, to stop erosion, communities need to do two things at the same time. First, they need to stop soil erosion by improving how they farm and graze their animals, so that the soil and plants can recover. At the same time, they need to restore the land that is already damaged, by filling gullies, digging bunds, and planting new grasses and trees.

Working Together to Fix the Land

The good news is that people can make a difference. In some areas of East Africa, the work people are doing together has actually reduced erosion [4]. Communities are using several traditional techniques. For example, they build bunds that collect water, soil, and seeds on farmland and grazing land (Figure 3). They also build farm terraces, which are gradual steps on hillsides where people farm. Terraces slow down water so it can infiltrate in the soil and reduce erosion. People have also been planting and protecting trees and grasses to hold soil in place, as well as mulching the leftover parts of crops to help stabilize soil and retain water.

Farmers in Ethiopia have even turned gullies into places to grow crops like coffee, earning money while restoring the land [5]. Students and scientists are learning how and where these efforts work, building the skills of the next generation of leaders. By working together with their neighbors, aid agencies, science, and nature, communities have shown that there is a way to bring damaged landscapes back to life and protect the environment for the future.

However, some gullies have grown too big for communities to fix by themselves. They need money, machines, and support from experts. These actions also need to happen all across East Africa, which is why they need help from their governments and the rest of the world. Only when everybody works together, from farmers to scientists to governments in different countries, can the land become healthy again.

Glossary

Soil Erosion: ↑ The process by which soil particles get washed away by rainfall or flowing water or blown away by wind. Erosion can remove both the top layer and deep layers of soil.

Volcanic Highlands: ↑ High, hilly areas formed by past volcanic eruptions. The rocks from cooled lava slowly break down into soils that can support farming and plant growth.

Fertile: ↑ Soil that contains many nutrients and minerals, and is good at holding water, allowing plants and crops to grow well.

Regime Shifts: ↑ Big, fast, and long-lasting changes in the landscape. They happen when human activities or environmental pressures push the land too far, after which it no longer behaves the same way.

Colonial Period: ↑ A time when European countries controlled and ruled parts of East Africa. They made the local people follow their rules and changed how people lived, farmed, and worked.

Nomadic Herders: ↑ People who move from place to place with their animals instead of staying in one village. They move to find fresh grass and water for their animals.

Gullies: ↑ Big, deep cuts in the landscape made by flowing rainwater that carries away eroded soil particles, nutrients, and water.

Bunds: ↑ Low walls or barriers made from soil, stones, or other materials, built along a field to slow down flowing water. Bunds help water sink into the soil and stop soil from washing away.

Conflict of Interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

This research was part of the AsFoRESEEN project, funded by the European Union through the Marie Skłodowska-Curie Actions of Horizon Europe grant number 101109315. Additional support was given by Flemish Interuniversity Council – University Development Cooperation (VLIR-UOS) through the project “From Monitoring to Managing Soil and Water Degradation in Tanzanian Gullies” grant number TZ2025SIN444A103.

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