1. Human Impact: Introduction
Although not the most numerous organisms on earth, humans have the greatest effect
on the environment.

2. How do humans usually impact the balance in ecosystems?
NEGATIVELY!

3. Why are humans disrupting the balance in ecosystems?
The human population shows exponential growth- it has
just reached 7 billion!!!
This large number of people puts a huge strain on
the environment.

4. How did this rapid growth occur?
Increased Food Supply
Improved Health Care
Improved Sanitation
and hygiene

5. Carrying Capacity- is the number of individuals the environment can support.
Limiting Factors- are factors in the environment that limit the size of populations.
What are some of our limiting factors?
Food, Water, Oxygen, Space

6. Carrying Capacity
time

7. Have we reached earth’s carrying capacity?
No, because we
continuously come up with new technologies
to produce more
Food.

8. What are some of the detrimental effects of overpopulation?
Over Consumption
Technology
Waste Disposal

9. What are some of the detrimental effects of overpopulation?
Overcrowding
Habitat Destruction
Industrialization

10. Deforestation

11. Deforestation Why? (PROS) : Provide land for farming
provide people places to live
Provide Resources to use in building or manufacturing
Effects  (Cons):
Deforestation leads to habitat destruction.
2) Organisms have no place to live.
Organisms can become endangered or extinct.
4) Biodiversity decreases.

12. Direct Harvesting
Organisms (plants and animals) are removed from the environment and NOT replaced.
Organisms are usually obtained through hunting or poaching (illegal hunting).
Often results in the loss or elimination of a species & a decrease in biodiversity.
Examples: Ivory, Exotic Birds

13. Non-native or Invasive species (Foreign or not belonging to)
Imported Species
Non-native or Invasive species
(Foreign or not belonging to)
Animal and vegetation species often become
invasive when introduced into environments lacking natural predators or other mechanisms to keep the dominating species in check.
These species become pests & disrupt the current ecosystem by reducing biodiversity.

14. The European Rabbit
Highly adaptable animal. Not a picky eater and breeds very fast.
Destroyed massive amounts of vegetation & reduced biodiversity.
In Australia, it spread like wildfire because its natural predators from back home, the weasel and fox, were not originally present.
The dingo and Tasmanian wolf, Australia's native carnivores (and potential rabbit consumers), were themselves being kept in check by local sheep and cattle ranchers.

15. New York’s Biggest Pest: Gypsy Moth
The Gypsy Moth originally
evolved in Asia & was
introduced here accidentally
in 1868.
What can happen when non-native species are
added to a new environment?
1)They often have no natural predators.
2)Rapidly overpopulate.
3)They then crowd out, feed on, or otherwise eliminate
native species.
4) Biodiversity decreases.

16. How do ecologists solve these pest problems?
*EXAMPLE: A virus was promptly released into the wild in Australia and effectively spread like wildfire through mosquito and rabbit flea bites, and killed all but 0.2% of the rabbits.
*This small percentage had built a resistance to the virus, bred like rabbits, and passed on the resistance to the virus.
Release a disease organism that is specific for the pest!

17. How do ecologists solve these pest problems?
Use of Pesticides or Insecticides:
*PROS: These chemicals/poisons can kill the pest.
*CONS: Can kill other organisms native to the ecosystem.

18. Biological Control
(LIVING CONTROL)
The release of natural predators of a pest species is a safe way to control pest problems without reducing diversity.
If a non-native predator is imported to control the pest, it may choose to feed on other native organisms reducing biodiversity.
Ex. The ladybug is released to eat aphids (bugs that eat crops).

19. What are the effects of farming?
*What happened to biodiversity?
*What happened to ecosystem stability?
*What would happen if an insect came along?
*What do farmers use to get rid of insects?
DECREASED
DECREASED