loss of forests, can also have a negative effect on soil quality. Healthy forests not only provide wood, but also hold soil in place, protect the quality of fresh water supplies, absorb carbon dioxide, and help moderate local climate

natural processes cannot replenish them within a reasonable amount of time

can be produced or replaced by a healthy ecosystem

In parts of the world with dry climates, a com bination of farming, overgrazing, sea- sonal drought, and climate change can turn farmland into desert.

what is habitat fragmentation?

When we burn fossil fuels in our factories and homes, we release nitrogen and sulfur compounds. When those compounds combine with water vapor in the air, they form nitric and sulfuric acids. These airborne acids can drift for many kilometer

occurs if a pollutant, such as DDT, mercury, or a PCB, is picked up by an organism and is not broken down or eliminated from its body. Instead, the pol- lutant collects in body tissues.

a layer in the earth's stratosphere containing a high concentration of ozone, which absorbs most of the ultraviolet radiation reaching the earth from the sun.

Gases that trap heat in the atmosphere

What causes soil erosion?

a gray-brown haze formed by chemical reactions among pollutants released into the air by industrial processes and automobile exhaust. Ozone is one product of these reactions.

Give an example of a nonrenewable resource.

Give an example of a renewable resource