Human influences on the environment
Trees leach nutrients when they are alive, but return nutrients to the soil when they die. When trees are cut down, nutrients get leached but not returned, resulting in infertile soil.
· Soil erosion
When trees are removed, soil can be washed away by rain as tree roots hold soil together (but there will be no tree roots, as there will be no trees).
· Disturbance of the water cycle
Trees take up water, when they are cut down, water runs straight into rivers, causing flooding. also, the local climate gets drier as there is much less transpiration occurring.
· Disturbance of the balance of carbon dioxide and oxygen
When trees die, carbon dioxide is naturally released. When they are burnt, all the carbon dioxide is released at once. alternatively, if wood is used in furniture the carbon is stored and not released, disrupting the carbon cycle.
Fewer trees mean fewer photosynthesis means less oxygen.
4.15 understand the biological consequences of pollution of water by sewage, including increases in the number of micro-organisms causing depletion of oxygen
· Like fertilisers, sewage also contains phosphates (from detergents) and nitrates (from faeces). If these are leaked into rivers, eutrophication occurs.
4.16 understand that eutrophication can result from leached minerals from fertiliser
· Nitrates and phosphates can leak from mineral fertilisers that are put on fields. If it rains, they are easily leached into rivers and lakes. this results in eutrophication. Basically...
- The extra nutrients causes algae to grow very fast. This blocks out the light
- Plants in the river (before the algae) cannot photosynthesise due to low light. They die.
- With more food (dead plants) available, microorganisms living in the water rapidly increase in number and deplete/use up all of the oxygen in the water.
- Organisms, like fish for example, that need oxygen, die.
4.14 understand how an increase in greenhouse gases results in...