resource that we need to grow food. Several factors contributed to the Dust Bowl storms.
First, farmers in the Central United States had plowed grasslands there to grow food crops.
They left the crop fields bare in the winter months. This left the soil exposed to wind.
Secondly, a long drought in the 1930’s left the exposed soil especially dry. When the spring
winds began blowing, the dry exposed soil was easily picked up and blown away.
We learned many lessons from the Dust Bowl storms. Today, we encourage farming practices
that keep the soil covered even during the winter, so that it is not exposed and vulnerable
to erosion. We have also learned of ways to prevent erosion in cities and towns as well as on
farmlands. In this lesson, you will learn about some human activities that lead to erosion.
You will then learn some of the specific ways we can prevent soil erosion.
Causes of Soil Erosion
Soil erosion occurs when water, wind, ice or gravity moves soil from one place to another.
Running water is the leading cause of erosion, since it can easily take soil with it as the water
flows downhill or moves across the land. Wind is the next leading cause of erosion. Just
as in the Dust Bowl storms of the 1930’s, wind can blow soil many hundreds of kilometers
away. Soil is especially vulnerable to erosion if it is bare or exposed. Plants therefore serve a
tremendous role in preventing soil erosion. If the soil is covered with plants, erosion is slowed
down. But when soil is bare, the rate of erosion speeds up tremendously. What are some
human activities that leave the soil exposed and speed up erosion? We speed up erosion
through the following actions:
- Agriculture
- Grazing animals
- Logging and mining
- Construction
- Recreational activities, like driving vehicles off-road or hiking
Agriculture, is probably the most significant human action that accelerates, or speeds up,
erosion (Figure19.3). We first plow the land to plant fields of crops. This takes away
the natural vegetative cover of an area and replaces it with rows of crop plants mixed with
bare areas. It also creates an area where there may not be anything growing in the winter,
because in most areas, food crops only grow in the spring and summer. The bare areas of
a field are very susceptible to erosion. Without anything growing on them, the soil is easily
picked up and carried away. The fields also experience more erosion in the winter if no plants
are growing on them and they are just left as bare soil. In addition, farmers sometimes make
deep grooves in the land with their tractor tires. These grooves act like small channels that
give running water a path. This speeds up erosion from water.
Some parts of the world use an agricultural practice called slash and burn. This involves
cutting and burning forests to create fields andpastures. It is one of the worldwide leading