Terrace farming primarily solves the problem of soil erosion on sloped land. By converting a steep hillside into a series of flat, stair-like steps, terraces slow the flow of rainwater, keep topsoil in place, and make agriculture possible on land that would otherwise wash away. Research in China found that existing terraces reduce cropland water erosion by 52%, and at some sites, terraces cut erosion by up to 99%.
But erosion control is just the starting point. Terracing addresses a web of connected problems, from water scarcity and nutrient loss to landslide risk and food insecurity in mountainous regions.
Soil Erosion on Slopes
When rain hits bare, sloped ground, it picks up speed as it moves downhill. That fast-moving water carries topsoil with it, stripping away the layer of earth that contains most of the nutrients crops need. On steep farmland without terraces, this process can remove inches of productive soil within a few seasons.
Terraces interrupt this process by breaking a long slope into short, level sections. Each flat step slows the water to a near standstill, giving it time to soak into the ground instead of racing downhill. The result is dramatic: a large-scale study of Chinese cropland found terraces cut water erosion in half overall. Under future climate scenarios with heavier rainfall, that benefit actually increases, with the total erosion prevented by terraces projected to grow by 15% to 63% through the end of the century. Proper maintenance and strategic placement of terraces can boost erosion reduction by an additional 45%.
Water Runoff and Moisture Loss
On sloped land, most rainfall runs off before it can soak in. This creates a frustrating paradox: a hillside farm can receive plenty of rain yet still leave crops thirsty. Terraces fix this by holding water in flat channels long enough for the soil to absorb it. The U.S. Natural Resources Conservation Service designs level terraces specifically to use soil infiltration as a natural outlet, meaning the terrace itself acts as a shallow basin that feeds rainwater directly into the root zone.
In dry regions, terraces are sometimes designed as moisture conservation systems. Engineers calculate the volume of water a terrace needs to collect to meet crop demands across an entire growing season. This approach turns terraces into a low-tech irrigation alternative, capturing and storing rainfall that would otherwise be lost. In Zimbabwe, tied-ridge systems (a form of in-field terracing) significantly reduced surface runoff and increased water infiltration, which led to deeper root growth and higher grain yields.
Nutrient Depletion in Hillside Soils
Erosion doesn’t just remove dirt. It strips away nitrogen, phosphorus, potassium, and organic matter, the nutrients that make soil fertile. Without terraces, hillside farmers often compensate by applying more chemical fertilizer each year, which raises costs and can pollute nearby waterways.
Terraces reverse this cycle. Research on loess plateau terraces found that potassium, nitrogen, and ammonium accumulate naturally in the surface soil of well-maintained terraces. Over time, this enriched topsoil functions almost like a natural fertilizer, reducing dependence on chemical inputs. The nutrient cycling improves soil structure year after year, creating a positive feedback loop: better soil holds more water, which supports more plant growth, which adds more organic matter back into the soil.
Limited Farmable Land in Mountainous Areas
Roughly 24% of the Earth’s land surface is mountainous, and many of the world’s poorest farming communities live in these regions. Steep slopes above about 15 degrees are extremely difficult to farm conventionally. Crops planted on them lose soil quickly, yields decline, and the land eventually becomes barren.
Terracing converts these otherwise unusable slopes into productive fields. In Ethiopia’s Anjenie watershed, terraced plots produced maize yields of 1.73 tons per hectare compared to just 0.77 tons on unterraced slopes. Barley showed an even more dramatic gap: 1.86 tons per hectare on terraces versus 0.61 tons without them. Those yield differences translate directly into household income and food security for smallholder families who depend on what they grow.
Landslide and Flood Risk
On steep terrain, the same erosion that degrades farmland also destabilizes entire hillsides. When heavy rain saturates loose soil on a bare slope, the result can be a landslide or mudslide that threatens communities downhill. Terraces serve as a critical line of defense.
A study of the Cinque Terre region in Italy found that well-maintained terraces dramatically reduced the severity of slope failures during extreme rainfall. Where dry stone terrace walls were kept in good condition, landslides were small and caused minimal damage to settlements. Where farmers had abandoned their terraces and stopped maintaining the walls, the same storms triggered widespread slope failures. The researchers concluded that terrace maintenance should be considered the primary measure for reducing landslide and flood risk in terraced watersheds.
The mechanism is straightforward. Intact terraces slow water movement across a hillside, lengthen the time it takes for rainfall to concentrate into streams, and reduce the volume of surface runoff. When terraces degrade, that hydrological connectivity snaps back, and water moves fast and destructively again. The Cinque Terre case showed that abandonment of traditional farming, and the terrace upkeep that came with it, was the main cause of catastrophic slope failures during heavy storms.
The Cost of Building Terraces
Terracing solves real problems, but it requires significant upfront investment. According to FAO data, a single worker can move only 3 to 4 cubic meters of earth in an eight-hour day when building terraces by hand. Adding topsoil preservation (setting aside the fertile top layer before construction and replacing it afterward) adds roughly 40 person-days of labor per hectare for manual construction.
Machines speed up the process considerably. A small bulldozer on moderate slopes can move about 20 cubic meters per hour, and larger equipment handles 40 to 45 cubic meters per hour. In Jamaica, machine-built terraces cost three to five times less than hand-built ones. Still, the construction costs are substantial enough that many smallholder farmers in developing countries cannot afford to terrace their land without outside support.
The investment pays off over time through higher yields, lower fertilizer costs, and reduced risk of losing the land entirely to erosion. But the long payback period means terracing programs often depend on government subsidies, community labor-sharing arrangements, or NGO support to get started. Once built, terraces require ongoing maintenance. Neglected walls crumble, drainage channels clog, and within a few years, the benefits reverse as the structures begin to accelerate rather than prevent erosion.