2. How Can People Change Ecosystems?

3. Pollution Humans and other living things need a clean place to live. This is why pollution (puh·LEW·shuhn) is a problem. Pollution happens when harmful substances are added to Earth’s water, air, or land. pollution

4. Water Pollution Sometimes wastes from homes or factories are dumped into rivers, lakes, and oceans. This causes water pollution. Polluted water can be too dirty to use. It can be dangerous, too. Some polluted water can make living things sick. When water becomes too polluted, it can kill the plants and animals that live in it. Water pollution is a problem for everyone.

5. Air Pollution Air pollution can come from forest fires or volcanoes. However, most air pollution comes from cars and factories. Burning gasoline, coal, and other fuels can pollute the air. They release compounds of sulfur and nitrogen called acids. The acids mix with water in the air and fall to Earth as acid rain. Acid rain can ruin lakes, forests, soils, and crops. Too much acid rain can harm many plants and animals.

6. Smog Waste gases and smoke from cars, homes, and factories may join with water in the air to form smog. Smog hangs in the air like a cloud. It can make the air harder to breathe. It also stings the eyes. You may have heard about smog alerts. When these are issued, people who have trouble breathing in smog should stay inside.

7. Land Pollution Acid rain, smog, and trash can all pollute soil. So can chemical wastes. This is called land pollution. Polluted land can harm the plants and animals that live on it. Land pollution can be ugly, too. Why do you think it is important to keep land clean?

8. Compare and Contrast How are smog and acid rain alike? How are they different? Find evidence to prove that different kinds of pollution are alike in some ways and different in others.

9. pollution Harmful substances added to Earth’s water, air, or land. Back to text