soil erosion

recreational activities

Recreational activities may accelerate soil erosion. Off-road vehicles disturb the landscape and the area eventually develops bare spots where no plants can grow. In some delicate habitats, even hikers boots can disturb the ground, so its important to stay on the trail (Figure 1.7). Soil erosion is as natural as any other type of erosion, but human activities have greatly accelerated soil erosion. In some locations soil erosion may occur about 10 times faster than its natural rate. Since Europeans settled in North America, about one-third of the topsoil in the area that is now the United States has eroded away. Deforested swatches in Brazil show up as gray amid the bright red tropical rainfor- est. (a) Disturbed land at a coal mine pit in Germany. (b) This coal mine in West Virginia covers more than 10,000 acres (15.6 square miles). Some of the exposed ground is being reclaimed by planting trees. Click image to the left or use the URL below. URL: (a) ATVS churn up the soil, accelerating erosion. (b) Hiking trails may become eroded. Click image to the left or use the URL below. URL:

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construction

Constructing buildings and roads churns up the ground and exposes soil to erosion. In some locations, native landscapes, such as forest and grassland, are cleared, exposing the surface to erosion (in some locations the land that will be built on is farmland). Near construction sites, dirt, picked up by the wind, is often in the air. Completed construction can also contribute to erosion (Figure 1.6).

logging and mining

Logging removes trees that protect the ground from soil erosion. The tree roots hold the soil together and the tree canopy protects the soil from hard falling rain. Logging results in the loss of leaf litter, or dead leaves, bark, and branches on the forest floor. Leaf litter plays an important role in protecting forest soils from erosion (Figure 1.3). Logging exposes large areas of land to erosion. Much of the worlds original forests have been logged. Many of the tropical forests that remain are currently the site of logging because North America and Europe have already harvested many of their trees (Figure 1.4). Soils eroded from logged forests clog rivers and lakes, fill estuaries, and bury coral reefs. Surface mining disturbs the land (Figure 1.5) and leaves the soil vulnerable to erosion.

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grazing

Grazing animals (Figure 1.2) wander over large areas of pasture or natural grasslands eating grasses and shrubs. Grazers expose soil by removing the plant cover for an area. They also churn up the ground with their hooves. If too many animals graze the same land area, the animals hooves pull plants out by their roots. A land is overgrazed if too many animals are living there. Grazing animals can cause erosion if they are allowed to overgraze and remove too much or all of the vegetation in a pasture.

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farming

Agriculture is probably the most significant activity that accelerates soil erosion because of the amount of land that is farmed and how much farming practices disturb the ground (Figure 1.1). Farmers remove native vegetation and then plow the land to plant new seeds. Because most crops grow only in spring and summer, the land lies fallow during the winter. Of course, winter is also the stormy season in many locations, so wind and rain are available to wash soil away. Tractor tires make deep grooves, which are natural pathways for water. Fine soil is blown away by wind. The soil that is most likely to erode is the nutrient-rich topsoil, which degrades the farmland. (a) The bare areas of farmland are especially vulnerable to erosion. (b) Slash-and-burn agriculture leaves land open for soil erosion and is one of the leading causes of soil erosion in the world.

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causes of soil erosion

The agents of soil erosion are the same as the agents of all types of erosion: water, wind, ice, or gravity. Running water is the leading cause of soil erosion, because water is abundant and has a lot of power. Wind is also a leading cause of soil erosion because wind can pick up soil and blow it far away. Activities that remove vegetation, disturb the ground, or allow the ground to dry are activities that increase erosion. What are some human activities that increase the likelihood that soil will be eroded?

instructional diagrams

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questions

which of the following natural phenomena can increase soil erosion?

a) a large reduction of rainfall.

b) a large increase of rainfall.

c) a forest fire.

-->  d) all of the above.

which farming activities often increase soil erosion?

a) plowing the land.

b) leaving land fallow (without plants) during winter.

c) disturbing the land with heavy machinery.

-->  d) all of the above.

how do grazing animals increase soil erosion?

a) they eat plants to the ground and expose soil.

b) their hooves churn up the ground.

c) their hooves pull plant out by the roots.

-->  d) all of the above.

human activities are the only cause of soil erosion.

a) true

-->  b) false

how do trees protect the ground from soil erosion?

a) tree roots hold the soil together.

b) a tree canopy stops the rain from falling so hard onto the ground.

c) leaf litter covers the ground and protects it.

-->  d) all of the above.

which of the following is true of the impact of recreational activities and soil erosion?

a) hikers and off-road vehicles both cause the same amount of soil erosion.

-->  b) off-road vehicles cause more soil erosion than hikers because they disturb more ground.

c) hikers do not cause soil erosion.

d) humans do not cause soil erosion.

parking lots and other manmade ground coverings may increase erosion around their edges.

-->  a) true

b) false

about one-tenth of the topsoil that was present in the united states before the arrival of europeans has now eroded away.

a) true

-->  b) false

the loss of topsoil to erosion is bad because

-->  a) topsoil contains most of the nutrients.

b) topsoil protects the rich organic material beneath it.

c) when the topsoil is gone it means that the entire soil profile has eroded away.

d) all of the above

the agents of erosion are water, ice, wind and gravity.

-->  a) true

b) false

diagram questions

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