1. Human impact on ecosystems

2. Human population growth and natural resources
Earth’s human population continues to grow
Earth’s carrying capacity
Technology and human population

3. Growth of the Human Population
Humans first reached North America at least 12,000 years ago, crossing the land bridge between Siberia and Alaska
Humans spread throughout North American and South America
About 2,000 years ago  130 million people on Earth
1650  500 million

4. Growth of the Human Population
Since then, average global birthrate has remained near 30 births per 1000 people/year
The death rate has fallen steadily with improvement in medical care and sanitation
2002 death rate  9 deaths per 1000 people/year
The world’s population continues to grow!

5. Growth of the Human Population
World’s population exceeded 6 billion in October 1999
About 260,000 people are added to the world population every day, or 180 people/minute
The global rate of population growth has been declining
Projected to stabilize by 2050 at 9.7 billion

6. The growing human population exerts pressures on Earth’s natural resources
Nonrenewable resource: natural resource that is used more quickly than it can be formed
Renewable resource: resource that replenishes itself quickly enough so that it will not be used faster than it can be produced

7. Effective management of Earth’s resources will meet the needs of the future
Ecological footprint: amount of land necessary to produce and maintain enough food, water, shelter, energy, and waste

8. Air quality
Pollution: anything that is added to the environment and has a negative affect on the environment or its organisms
Smog: air pollution in which gases released from burning fossil fuels form a fog when they react with sunlight
Particulate: microscopic bits of dust, metal, and unburned fuel produced by industrial processes

9. Acid Rain Precipitation
pH below normal
Unusually high concentration of sulfuric or nitric acids
Often a result of chemical pollution of the air:
Automobile exhausts
Burning of fossil fuels

10. What is the impact of acid rain?
Rainwater and some soils are naturally acidic
The acidity added by human activity is having a dramatic effect
USA and Canada thousands of lakes are “dying” as their pH levels fall far below 5.0
Forests in the eastern USA and southern Canada are being damaged
The symbiotic fungi in tree roots cannot survive

11. The Ozone Layer O3, a protective shield in the upper atmosphere
1985 disintegration of the ozone layer was evident from satellite imagery back to 1978
The ozone hole continued to grow larger
Allowed for more UV radiation to reach the Earth’s surface
Increase chances of skin cancer, cataracts, etc.

12. What is Destroying Ozone?
Chlorofluorocarbons (CFCs):
Hydrocarbons in which some or all of the hydrogen atoms are replaced by chlorine and fluorine
Invented in the 1920s, used in coolants for refrigerators and air conditioners and in cleaning solvents
Use is restricted because they destroy the ozone
High in the atmosphere, UV radiation from the sun is able to break the stable bonds of CFCs
The free chlorine atoms enter a series of reactions that destroy ozone

13. Air pollution is changing Earth’s biosphere

14. Greenhouse Effect
The warming of the surface of Earth and the lower atmosphere
A result of carbon dioxide and water vapor; which absorb and reradiate infrared radiation

15. Global Warming
The average global temperature has been steadily increasing for more than a century, particularly since the 1950s
Global warming is often followed by centuries of cold
Sunspot cycles may contribute to these cyclical changes in global temperature
Human activity is significantly contributing to global warming in modern times

16. Water quality Water pollution affects ecosystems
Indicator species: species whose presence in an ecosystem gives clues about the conditions of that ecosystem

17. Biological Magnification
The accumulation of increasingly large amounts of toxic substances within each successive link of the food chain
Examples: DDT, pesticides

18. Threats to biodiversity
Preserving biodiversity is important to the future of the biosphere
Loss of habitat eliminates species
Habitat fragmentation: process by which part of an organism’s preferred habitat range becomes inaccessible
Introduced species can disrupt stable relationships in an ecosystem
Introduced species: species that is not native and was brought to an area as a result of human activities

19. Threats to biodiversity
Effects on native species
Economic damage

20. Loss of Resources
Nonrenewable resources are being consumed or destroyed at alarming rates
Extinction of species
Loss of topsoil
Ground-water pollution and depletion

21. Extinction of Species
½ the world’s tropical rainforests have been burned to make pasture or farmland in the last 50 years
No one knows how many species are being lost
As a species disappear, so do our chances to learn about them and to learn about their possible benefits

22. Loss of Topsoil
The USA is one of the most productive agricultural countries on Earth, largely because of its fertile soils
The topsoil cannot be replaced and it is being lost at a rate of several cm/decade
Since 1950 the world has lost 1/3 of its topsoil, primarily because of human activity

23. Ground-Water Pollution & Depletion
Aquifer: A porous rock that stores and allows the flow of ground-water
Water seeps into aquifers too slowly to replace the large amount of water being withdrawn
There is not much effort to conserve ground water
Large amounts are wasted on watering lawns, washing cars, leaky and inefficient faucets and toilets

24. Ground-Water Pollution & Depletion
A great deal of ground water is being polluted by irresponsible disposal of chemical wastes
Once pollution enters the ground water, there is no effective way to remove it

25. conservation
Sustainable development manages resources for present and future generations
Rotation
Fishing gear review
Harvest reduction
Fishing bans

26. Conservation practices focus on a few species but benefit entire ecosystems
Umbrella species: species whose being protected under the Endangered Species Act leads to the preservation of its habitat and all the other organisms in its community

27. Protecting earth’s resources helps protect our future
Protecting natural resources
A sustainable Earth
A worldwide effort is needed!
Early 1990s international agreement to stop CFC production
The release of many dangerous industrial and agricultural chemicals has been restricted in the USA
Efforts to reduce pollution: Clean Air Act of 1990

28. What Can You Do?
Conserve energy by walking, riding a bike, or taking public transportation
Do a resource-and energy-use inventory of your home
Learn about the environment
Recycle newspapers, aluminum products, glass and plastic
Create rich soil by making your own compost heap from leaves, grass and fruit peelings