Slides in Chapter 4 - Conserving Land and Soil
People use land in many ways. Three uses that change land are agriculture, development, and mining.
Land is the source of most food. To provide food for a growing population, new farmland must be created by:
clearing forests, draining wetlands, and irrigating deserts
The construction of buildings, roads, bridges, dams, and other structures is called development. Development reduces the amount of farmland, but can also destroy the wildlife habitats.
Mining is the removal of non-renewable resources from the land. Strip mining involves removing a strip of land to obtain the minerals and then replace the strip. Strip mining exposes the soil. Then the soil can be blown or washed away. For resources located deep underground, tunnels are dug and minerals are carried up. This is called underground mining.
We will now watch two videos that deal with the importance of soil:
Litter: top layer composed of dead leaves and grass
Topsoil: mixture of rock fragments, nutrients, water, air, and decaying animal and plant matter.
subsoil: below topsoil; contains same materials as topsoil, but less animal and plant matter.
bedrock: rock that makes up Earth's crust
Rich topsoil takes a long time to form, so it is important to protect Earth's soil.
If the soil is not taken care of these problems can develop:
EROSION, NUTRIENT DEPLETION, DESERTIFICATION
The process by which water, wind, or ice moves particles of rocks or soil.
Sometimes when a farmer plants the same crops in a field year after year the soil becomes less fertile. One way to prevent this is to periodically leave a field unplanted with crops (this is called fallow). A second way is to leave stalks and vine decompose in the fields to enrich the soil.
A third way is to rotate crops - which means plant different crops on alternate years because they bring different nutrients into the soil.
The advance of desertlike conditions into areas that were once fertile is called desertification.
Climate, overgrazing with cattle, and cutting down too many trees can cause this.
The process of restoring land damaged by erosion is called land reclamation.