1. Populations and Human Impact on the Ecosystem

2. Population population density of living
A group of individuals of the same species in a given area
Population Density – the number of individuals of
a species in a given area
Under ideal conditions , the
population density of living
things can increase explosively
-Elephant seals – hunted nearly to
extinction (20 individuals) 1890
Population in 1991
127,000 and growing
exponential growth
Elephant seals hunted to 20 individuals- once hunting was banned – the seals were able to exploit an environment with virtually limitless resources – numbers increased exponentially

3. Elephant Seals –
were hunted to near extinction ( individuals) in 1890
Hunting was outlawed
Numbers began to increase
127,000 seals by 1991

4. Carrying Capacity Populations can’t continue to grow indefinitely –
Limiting Factors - Limit the number of organisms in an ecosystem
- productivity of ecosystem (food supply)
Carrying Capacity - the greatest number of individuals
in a population that an ecosystem can support at a given time
-when a population exceeds carrying capacity it will decline
- predators
- seasonal changes in the ecosystem
- disease
- cover
- water

5. During times of population increase, birthrate exceeds death rate
During times when population declines death rate exceeds birth rate

6. Deer on the Kaibab Plateau – Good Intentions Gone Bad

7. Lessons from Kaibab
When a population density greatly exceeds carrying capacity, the ecosystem is damaged
- leads to a crash in population density
- carrying capacity of the ecosystem is permanently reduced

8. What is Human Carrying Capacity

9. Human Impact on Biogeochemical Cycles
Two activities caused significant changes in carbon cycle:
Burning Fossil Fuels – releases large amounts of CO2
Converting forests to agricultural land – reduces the amount of CO2 that is removed from the atmosphere
Excess CO2 traps heat
raising average global
temperature - Global
climate change

10. Global Climate Change Concerns Melting glaciers and rising sea Levels
Water shortages
Warmer ocean surface temperatures = more intense hurricanes
Pestilence – insects and disease
Habitat loss – coral reefs, alpine meadows, tundra
Species loss – polar bear (food), green sea turtle (nest), North Atlantic right whale (food), giant panda (food), orangutan (fire), elephants (drought), frogs (reproduction), and tigers (habitat)

11. Phosphorus Cycle Plants and animals require phosphorus
to make nucleic acids
- it is locked in rocks rocks
- natural erosion
releases phosphorus
- humans mine it and
use as a fertilizer
finds its way into
lakes etc…..

12. Human Impacts N & P Cycles
Use of Nitrogen and Phosphorus as fertilizers –
-produces large quantities of food (good)
- excess fertilizer runs into lakes, streams etc… (bad)
- algae blooms and then dies.
- dead algae decompose using up the oxygen
in the water

13. Human Impact Acid Rain
Acid rain – Sulfur emissions from burning fossil fuels fall as acid rain – kills forests and aquatic life

14. Human Impact – Ozone Depletion
Ozone (O3) depletion – Ozone layer which protects us from UV radiation is being damaged by CFC’s = greater risk of cancers

15. Human Impact – Air Pollution - Smog
Smog – air pollutants – damage lungs shortens life

16. Human Impacts – Water Pollution

17. Water Pollution – Cuyahoga River
The following is from a 1968 report on the Cuyahoga River
The surface is covered with the brown oily film observed upstream as far as the Southerly Plant effluent. In addition, large quantities of black heavy oil floating in slicks, sometimes several inches thick, are observed frequently. Debris and trash are commonly caught up in these slicks forming an unsightly floating mess. Anaerobic action is common as the dissolved oxygen is seldom above a fraction of a part per million. The discharge of cooling water increases the temperature by 10 to 15°F. The velocity is negligible, and sludge accumulates on the bottom. Animal life does not exist. Only the algae Oscillatoria grows along the piers above the water line. The color changes from gray-brown to rusty brown as the river proceeds downstream. Transparency is less than 0.5 feet in this reach. This entire reach is grossly polluted.
The river has caught fire at least 13 times the last time was 1969

18. Aftermath of the 1969 Fire
Legislation was passed to clean up lakes and streams
- the Clean Water Act – passed in 1972 set standards for surface water quality
- essentially all navigable surface water must be fit for human sports and recreation.
- The Environmental Protection Agency was created
Cuyahoga river today

19. Human Impacts – Soil Erosion
Soil can take up to 1000 years to form 1 inch
Once topsoil is lost, it is effectively gone for good