6.2 Using Resources Wisely

Soil is a renewable resource, but it must be managed properly.

Soil erosion is the wearing away of surface soil by water and wind.

In dry climates, farming and overgrazing change farmland into deserts, a process called desertification.

Deforestation is loss of forests. Because healthy forests hold soil in place, deforestation increases erosion.

Sustainable uses include leaving stems and roots of previous crops in place, crop rotation, contour plowing, terracing, selectively harvesting mature trees, and tree farms.

The amount of fresh water is limited, and some sources cannot be replaced.

A pollutant is a harmful material that can enter the biosphere. Water pollutants come from industrial chemicals, residential sewage, and other sources.

Many chemical pollutants become concentrated in organisms at higher trophic levels of the food chain through biological magnification.

Sustainable uses include conservation, pollution control, and watershed protection.

Clean air is important to human health and Earth’s climate. Pollution reduces air quality.

Smog is a mixture of chemicals formed from emissions from cars and industry.

Burning fossil fuels releases compounds that join with water in air, forming acid rain.

Greenhouse gases, such as carbon dioxide and methane, can cause global warming.

Particulates are microscopic particles that cause health problems.

One way of sustaining air quality is controlling automobile emissions.