How can stone steps turn a steep hillside into farmland?

On a steep hillside, rainwater can run downhill quickly and carry loose soil with it. Farmers in Shexian, in China's Taihang Mountains, have built stone-edged terraces: flatter growing areas arranged like very large steps.

The stone edge supports soil behind it. The flatter surface shortens the steep path that water would otherwise follow. Water has more chance to enter the ground instead of sweeping straight down the slope. Keeping soil in place also helps keep the nutrients and roots within it. The steps do not create rain; they help people use the rain that arrives.

Shexian's terraces are not all flooded rice fields. This is a dryland farming system, with crops and trees suited to its setting, including walnuts and Chinese prickly ash. Local farmers have developed ways to manage stone, soil, crops and rainfall together over many generations. The shape of the land and the knowledge of the people both matter.

Terraces need continued care. A damaged wall or badly directed flow can let water erode the soil it was meant to protect. The same hillside that looks like a staircase from a distance is a living water-and-soil system close up. Its useful shape helps plants grow where unprotected soil would be much easier to lose.