Biology 3A – human impact

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 Normal – Some greenhouse gases present Radiation from sun reaches Earth Some absorbed Some reflected and leaves Some reflected, but bounces back and warms Earth • 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 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 Normal Ozone prevents most of UV radiation from entering • 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 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