How are Humans Affecting the Environment? Human Overpopulation Deforestation Loss of Biodiversity Pesticide Use Bio Magnification Poor Air Quality Poor Water Quality Loss of Natural Resources Ozone Depletion

Worldwide, about half of the area covered by forests has been cleared. Human Impact on the Environment 1. Effects of Human Overpopulation: loss of land/habitat water and food shortage poor sanitation species extinction poverty emerging disease 2. Deforestation – loss of forests - cause soil erosion, loss of habitat, and species extinction Worldwide, about half of the area covered by forests has been cleared. 3. Loss of Biodiversity – the variety of organisms in an ecosystem - an imbalance can cause extinction 4. Pesticide Use – using chemicals to kill and control pests - will sometimes kill non-target species - pollutes water sources - causes health problems 5. Biological Magnification/Bio Accumulation – concentrations of a harmful substance increase in organisms at higher trophic levels in a food web

6. Impact on Air Quality Global Warming Acid Rain Atmospheric greenhouse gasses (CO2, water vapor, and methane) trap heat = rain that has been made acidic by certain pollutants in the air this warms planet Earth affects climate and weather raises sea level affects health of ecosystems pollutants = sulfur dioxide and nitrogen oxides from burning fossil fuels causes health problems damages forests and lakes damages buildings

Brain Pop Global Warming Air Pollution (Acid Rain) http://www.brainpop.com/science/earthsystem/greenhouseeffect/ Air Pollution (Acid Rain) http://www.brainpop.com/science/ourfragileenvironment/airpollution/

7. Impact on Water Quality The runoff of silt, soil, pesticides, and fertilizers from agricultural land is the largest single source of water pollution. 8. Eutrophication: - excess detergents and fertilizers can run off into lakes and ponds - this stimulates plant and algae overgrowth - a buildup of algae can lower the levels of dissolved oxygen in the water - this leads to the dying off of the fish population Why can’t you just clean up polluted water? - it is expensive - Who is to pay for it? - Technology not available for all types

8. Impact on Natural Resources Renewable Resources - can regenerate if they are alive or can be replenished by biochemical cycles if they are nonliving - ex. trees, fresh water Nonrenewable Resources - cannot be replenished by natural processes - ex. fossil fuels Sustainability = a way of using natural resources without depleting them for future generations use renewable resources that can be “restocked” recycle and reuse products plant tree farms only cut down selected trees instead of clear-cutting follow emission standards 6

The Story of Easter Island Humans first landed on Easter Island between 400 and 700 A.D. Island had thick forests, rich soil, many bird and animal species Human population grew quickly over next 1000 years They cut down forests for lumber and boats faster than the trees could grow back Eventually, there were no trees left….no wood for shelter or boats, rich soil washed away, habitat lost for animal species, no fishing without boats With no food, and island resources nearly gone, the Easter Island human population crashed and the Easter Islanders disappeared

Depletion of the Ozone Layer A thin layer of O3 gas located in the stratosphere Filters out (and protects us from) harmful UVA rays emitted by the Sun UVA rays cause cataracts and skin cancer

How is the Ozone being depleted? From the use of chlorofluorocarbons (CFC’s) CFC’s are chemicals used in Aerosols Styrofoam Cooling agents in refrigerators and air conditioners Kept sealed, CFC’s pose no threat to the environment, however, once released to the atmosphere, they break ozone molecules apart. Thus, the ozone hole.

What has been done to protect the ozone layer? The Montreal Protocol Developed in 1987 by Canada Treaty signed by several countries to limit the use of CFC’s CFC’s have now been completely phased out As a result, our ozone is regenerating

Brain Pop – The Ozone Layer http://www.brainpop.com/science/earthsystem/ozonelayer/ O3 = Ozone