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Desertification

Topic

Our Growing Deserts
Desertification

What Causes It

Desertification is when a grassland becomes a desert. Many grasslands throughout the world survive on only a few inches of rain per year more than a desert. Yet they provide grass for countless animals. The grass also holds the soil in place, preventing erosion. Sometimes, a long dry spell will affect the grassland to make it turn desert, but scientists have found that much of the world's desertification is due to the actions of humans.

Over-grazing does the most damage to grasslands that experience desertification. If a dry grassland is overgrazed by cattle, horses and sheep, it loses the little protection it has against erosion. The plant roots that help the soil stay in place are lost so it blows away and washes away. Soon you have a new desert. Clearing forest can have a similar effect if all the vegetation is taken at once. This is done with the slash and burn technique for clearing land. The topsoil blows or washes away. An entire river valley can turn to desert if the river is rerouted upstream for agricultural irrigation or drinking water for a nearby urban area. More than 40% of the Earth's land is thought to be dry (arid or semi-arid) and has more than 2 billion people living there. Scientists think that 24 billion tons of topsoil are lost to erosion every year.

How Does It Affect Us

In the United States, in the 1930s, the great plains underwent a drastic desertification from too many animals grazing it at once, too much plowing under of the natural prairies at once and then an unusual drought. This caused the dust bowl that lasted for ten years and fueled the great depression. So, desertification can affect the humans that cause it and in turn cause terrible hardship to those humans -- us!

In Russia, the Aral Sea became a desert because of human actions. All the freshwater rivers that drained into the Sea were rerouted upstream for agricultural irrigation. Without its freshwater inlets, the Sea shrank and got saltier. It got so salty that all the fish died. The seabed exposed to the air was a flat, salt desert. To make things worse, the salty sand left behind blows out into the hills and ruins farm fields. Giant ships lay on their sides, stranded out in the sand when the sea dried up.

What Has Been Done to Fix It

In 1994, the United Nations developed the UN Convention to Combat Desertification (UNCCD). More than 175 nations have signed and ratified an agreement to help. They believe that if we help people have a better way to get food and the things they need, there will be less land abuse and so less desertification.

What Can You Do to Help

People can help stop desertification by not grazing too many animals at one time in dry areas, planting trees to protect soil and building sand fences to block winds. All these things will help slow desertification.

Post Assessment Quiz

(Included in PDF)

Desertification - Read and React

1. Give two reasons why desertification occurs:

2. Why is grass important for preventing desertification?

3. Name two reasons why rivers are rerouted:

4. Name one big event in the United States in the 1930s that was causes by desertification:

5. Name one thing people could do to decrease rainforest desertification:

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