What causes sandstorms, and how can we reduce them?

How it works

When strong wind sweeps across dry ground with no plants to protect it, sand grains start hopping and knock finer dust into the air. The heavier sand mostly bounces along near the ground, but the light dust can rise high and travel far, turning the sky yellow-brown and hiding the sun.

Sandstorms make it hard to breathe and to see, and sand gets in people's eyes. Drivers and pilots can't see far ahead. Blowing sand can also bury farms and roads and strip away the rich top layer of soil that crops need.

The key to fixing sand is to give the ground a coat. People press straw into the sand in chequerboard squares and plant tough grasses and shrubs. Roots knit the sand together like a net, and leaves slow the wind near the ground. Northern China has planted huge belts of trees and shrubs over many decades to hold back the sand.

Where to see it in New Zealand

Sandstorms are rare in New Zealand, but big Australian dust storms sometimes blow red dust across the Tasman Sea. It can settle on the snow and glaciers of the Southern Alps, tinting them red or orange. On New Zealand beaches, people plant native pīngao and spinifex to stop the sand from blowing away.

Try it together

Spread dry sand in two shallow trays. Leave one bare, and push a few tufts of grass or a layer of leaves into the other. Outside, wearing sunglasses, blow gently across each tray through a straw. Which tray loses more sand?