Mountain Staircases: Farming on Terraces
Farmers prefer flat land, but in many mountainous regions flat land is rare. Rather than give up, farmers in places such as the Andes in South America and the highlands of Southeast Asia have carved steep hillsides into steps. These flat strips, called terraces, look like giant green staircases climbing the slopes.
Building a terrace is hard work. Workers dig into the slope, level a strip of ground, and build a wall along the outer edge, often from stacked stone or packed earth. The flat part is filled with soil, sometimes brought from elsewhere, so the plants have plenty of depth for roots.
The steps solve two problems. On a steep, unplanted slope, heavy rain washes soil downhill, a process called erosion, and the richest topsoil goes first. A terrace slows the water so that it soaks in rather than rushing away. This keeps the soil in place and gives plants more moisture. The steps also make planting, weeding, and harvesting safer and easier than working on a slant.
Some terraces are designed to hold water. In rice farming, a level terrace can be flooded with a shallow layer of water, and the walls keep it from draining away. Water often flows from the highest terrace to the next one down through small channels, so a single stream can serve a whole mountainside. Many terraces have been farmed and repaired for hundreds of years, which shows how well the design works.