Sometimes the difference between a desert and a dry grassland is just a few inches of rain per year. The grasses hold the soil in place and the habitat, though dry, is relatively stable. With desertification this all changes. There are many reasons why a grassland turns into a desert, and the one you might think is the most obvious — a long drought — is actually rarely the reason! It is almost always due to the actions of humans that desertification changes a habitat.

Transform a Tire

In 1989, only 10 percent of the scrap tires in the United States were reused. Thankfully, things have changed! To find out how many tires are now recycled, look at the pairs of tires below. Some look like they are linked through each other. Others look like two tires that overlap, but are not linked. Read the letters (from left to right, top to bottom) that are in the unlinked tires.

Environmental Experiment

Noise Pollution and Learning

Can noise pollution keep you from learning?

With a group of friends try this experiment. You will need two rooms, a pair of earplugs, two copies of a short poem (4 lines or less).

• Choose two people as learners. They each get a copy of the poem to learn.

• Put one person in a room with the door closed and earplugs in their ears. They have 5 minutes to learn the poem by heart.

• The other person sits on the floor of the second room while you and a couple of friends talk and make noise around them. They have to try and memorize the same poem in 5 minutes as well. They cannot cover their ears.

• At the end of 5 minutes bring both learners into one room. Have the noise victim try and recite the poem out loud from memory first. Then have the silent learner try. Who remembered more of the poem? What does this tell us about noise pollution and learning?

In the 1930s the great plains of the United States experienced desertification from overgrazing, poor farming practices, and drought. It was called the “dust bowl” and lasted for ten years and caused huge hardship to many people.

One big reason for desertification is overgrazing. A semi-arid grassland that is overgrazed by cattle loses the little protection it has. With no plant roots left to hold it in place, topsoil blows away in the wind or washes away in the next rain. The land becomes a desert. Twenty-four billion tons of topsoil are lost every year to erosion by wind, water, and other causes.

Another way desertification happens is when a forest is completely cleared by slash-and-burn technique. This is when all the trees are cut down and then everything is set on fire to burn it away. The thin topsoil that is left exposed to the elements has nothing to hold it in place, and just like overgrazed land, the soil blows away in the wind or washes away in the next rain.

A river valley can turn into a desert when people reroute water from the river upstream for irrigation or to supply a city with drinking water.

An extreme case of desertification caused by irrigation happened in Russia with the Aral Sea. The rivers that fed into the sea were diverted to irrigate dry lands for farming. Over time the sea began to shrink. As it shrank, the water got saltier. Soon it was too salty for the fish to live. The sea was dead. Where it dried up, it left a flat, salt desert. Now when the wind blows, the salty sand blows out into the hills and ruins surrounding farm fields. In some places giant ships sit stranded out in the sand as if they were dropped from space. This is one extreme result of man-made desertification.

People are trying to take measures to stop desertification throughout the world. Limiting grazing animals in dry areas and planting trees or building sand fences to block winds helps to slow the process, but it will be a constant challenge to keep the desert from creeping into our drier lands.