1. Human Impact on Ecosystems Chapter 3 Section 1

2. Human population growth presents challenges

3. Human population is increasing  Just 200 years ago the human population was only 1 billion.  Today it is estimated that the current population is 6 billion.  This increase has happened in a very short time.  It is expected for the population to grow to 9 billon by the year 2050.

4. Humans put pressure on ecosystems  Resources such as food, water, and space can be limiting factors for biological populations.  As the human population grows, it uses more resources; the activities of the growing human population are putting pressure on Earth's ecosystems.

5. Pressure #1: Waste Disposal  Most garbage and trash ends up in landfills.  Why are landfills bad?  They take up a lot of space.  Decomposing trash can release dangerous chemicals into the air as well as harmful chemicals into the ground.

7. Pressure #2: Resources are limited  A natural resource is any type of material or energy that humans use to meet their needs.  Natural resources that humans take from their environment include water, food, wood, stone, metal, and minerals

8. Pressure #2: Resources

10. Pressure #3: Urban Growth  Population density: the measure of the number of people in a given area.  High population density = _____________ impact on ecosystem  Low population density = ____________ impact on ecosystem

11. Pressure #3: Urban Growth  Population density is high in cities.  Buildings are spaced close together and there are a large number of people in a small area.  This changes the landscape.  Resources exceed what is available in the local environment so they must come from farther away.

12. Pressure #3: Urban Growth

13. Pressure #4: Expanding Land Use  Natural habitats are destroyed by expanding communities.  Cutting down trees affects the carbon cycle.  Soil that was held by roots may now wash into lakes and rivers.

14. Pressure #4: Expanding Land Use  Productive farmland is lost to urban development.  When cities spread out there is more need for cars. This adds to the pollution in our air