1. KEY CONCEPT As the human population grows, the demand for Earth’s resources increases.

2. Earth’s human population continues to grow.
Earth’s human carrying capacity is unknown.
Fig. shows how population size has changed over time. Today’s human population is over 7 billion. In the future will Earth support 10 billion people, 20 billion or even 50 billion people?

3. Technology has helped to increase Earth’s carrying capacity.
gas-powered farm equipment
medical advancements

4. The growing human population exerts pressure on Earth’s natural resources.
Nonrenewable resources are used faster than they form.
coal
Oil
In 2006, the human population was using oil at a rate of 77 million barrels per day and world oil usage continues to rise.

5. Growing use of nonrenewable resources may lead to a crisis.
Renewable resources cannot be used up or can replenish themselves over time.
wind
water
sunlight
Growing use of nonrenewable resources may lead to a crisis.
Resources must be properly managed.
Fig. Giant wind turbines such as these capture renewable energy from Earth's natural processes.

6. Earth’s resources must be used responsibly.
Effective management of Earth’s resources will help meet the needs of the future.
Earth’s resources must be used responsibly.
Careless use of resources makes them unavailable to future generations.
Easter Island is an example of irresponsible resource use.
They found out that
using trees faster than
they can grow back is an
unsustainable practice.
Read about this on page 456.

7. An ecological footprint is the amount of land needed to support a person.
The land must produce and maintain enough
food and water
shelter
energy
waste

8. Several factors affect the size of the ecological footprint.
amount and efficiency of resource use
amount and toxicity of waste produced
Fig. Different regions of the world have varying levels of impact on their environment. This graph shows the average ecological footprint of individuals around the world.