Populations and Human Impact on the Ecosystem

1. Populations and Human Impact on the Ecosystem

2. Population • 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

3. Elephant Seals – were hunted to near extinction (8 - 20 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. HumanImpact – 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 Oscillatoriagrows 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