1. Biology 3A – human impact

2. Salinity
Trees have long roots and draw up water from deep underground – keeping water table low
Grasses have shallow roots and do not draw up the same amount of water
When trees are cleared for pasture or houses, the water table rises, bringing salts to the surface

3. Deforestation Forests provide habitat for a number of rare species
Removal of habitat leads to loss of these species
Large amounts of vegetation increase humidity – removal can change rainfall patterns
Loss of vegetation often leads to erosion, salinity and desertification
Forests are a way of fixing CO2 – as trees are large, slow growing and long lived, so removing trees increases green house effects

4. Desertification Main causes clearing for houses, farms, mining etc
Main effects
loss of soil fertility
loss of habitat
soil erosion
Salinity
decreased humidity and rainfall
damage to waterways – fertilizers & pesticides

5. Eutrophication
Increased nutrients (especially nitrates and phosphates) from fertilisers, detergents and sewage enter water ways
Blue-green algae increase growth rate leading to population explosion
This rapid growth uses up the oxygen in the water, causing other organisms to die, and then the blue-green algae to die
Many species of blue-green algae produce toxins – when population numbers are high these are produced in such large numbers that they kill other water life
As there is little or no oxygen, dead organisms rot anaerobically – leading to the bad smell

6. Ecological magnification
This is build up of pollutants eg insecticides, heavy metals in a food chain. The higher order consumers and detrivores have the highest levels
Problems seen include
Death of top order consumers eg hawks, falcons
Plagues of lower order consumers due to lack of predators eg mice plague because owls have been poisoned
Heavy metal poisoning in people eating high order consumers or detrivores eg shellfish

7. Enhanced Greenhouse effects - global warming
Main causes
Build up of greenhouse gases in the atmosphere – carbon dioxide (combustion), methane (ruminants & rotting garbage) & CFC’s (refrigerators & air conditioners)
Main effects
Increased global temperatures 
Rise in sea levels (thermal expansion & polar icecap melting)
Melting of glaciers
Changes in weather patterns – some places (eg Australia get dryer, others getter wetter)
Possible solutions
Reduce emissions
Plant more trees, use less fossil fuels, reduce ruminants
Normal –
Some greenhouse gases present
Radiation from sun reaches Earth
Some absorbed
Some reflected and leaves
Some reflected, but bounces back and warms Earth
Global warming–
Increased greenhouse gases present
Radiation from sun reaches Earth
Some absorbed
Less reflected and leaves
More reflected, and bounces back and warms Earth

8. Enhanced Greenhouse effects - global warming 2

9. Global currents & climate
Global currents drive many of our weather patterns and also determine productivity of many marine ecosystems
A change in salinity at the ventilation areas could lead to a reduction in the current  changes in climate.
A decrease in surface temperature means less CO2 is trapped

10. Climate change – is it happening?
Previous ice level
Food resources scarcer so bears are looking after cubs for 2 years, instead of 1  breed every 3rd year instead of every 2nd year
Average rainfall decreasing
Athabasca glacier
Healthy pines
Pines affected by pine beetle
Lake Louise – May 26th 2008 (last month of spring) – still frozen
More pines are affected by pine beetle – winters not cold enough to kill off adult beetles

11. Deterioration of the ozone layer
Main causes
CFC’s, halons & methyl bromine (& jet planes) destroy ozone in atmosphere
Main effects
Ozone (O3) absorbs UV radiation.
If ozone is reduced more radiation gets through
This leads to increased temperature
Higher radiation  increase risk of skin cancers & eye problems in people, higher risk of mutation & damage in unicellular organisms
Damage to algae may cause loss of biomass/ ecosystem collapse in marine ecosystems
Possible solutions
Reduce use of CFC’s
Care with disposal of gases (eg old refrigerators, servicing air conditioners
Normal
Ozone prevents most of UV radiation from entering
Ozone depletion
Less ozone means more UV radiation can enter

12. Ozone depletion Ozone depletion over south pole
Dobson units measure amount of ozone present