Component 1.6 - Agricultural Exploitation Flashcards
How has farming diminished biodiversity?
1) Hedgerow removal
2) Monoculture
- same crop extract same minerals from same depth of soil therefor it has increased the use of inorganic fertilisers
- Same species = same pests which increases in number so more insecticides
3) Overgrazing of cattle
- Hooves compact soil, pushes out air and prevents water and roots entering. Grass for grazing cattle cannot grow
What are the reasons for deforestation?
- Land is cleared for farming
- High value trees may be targeted
- New roads to provide a transport infrastructure
- Timber is used as building material, fuel etc
Consequence of deforestation - soil erosion
Tree roots bind soil together, when it rains heavily top soil can be sweeped from higher slopes in valleys. Top soil is the fertile soil and what remains is not suitable for crop growth
Consequence of deforestation - flooding leading to waterlogged soil
- Deforestation causes lowland flooding
1) Evaporation returns water vapour to the atmosphere more slowly than transpiration (when trees were there)
2) Water fills the soils airspace’s so there is less oxygen available for roots
3) Wet soil takes longer to warm up which doesn’t favour germination or root activity
4) Cold, damp soil favours denitrifying bacteria
Consequence of deforestation - less rainfall
Due to evaporation being slower than transpiration water is returned to the atmosphere more slowly. This accelerates desertification.
What are other effects of deforestation?
- Habitat loss leading to reduced biodiversity
- Increase in atmospheric carbon dioxide (less photosynthesis, burning and decay of trees)
What are the methods of forest management?
- Slash and burn
- Coppicing
- Selective cutting
Describe the process of slash and burn and explain why it is used
- A small area is cut and burned
- People grow crops on soil fertilised with ash from the burnt trees
Describe the process of coppicing and why it is used?
- Tree trunk is cut leaving a stool and new shoots emerge from buds in the stool
- This has a long rotation time which is sustainable as many years are left between harvesting the trees
What is selective cutting and state why it is used?
- Felling only some trees in an area
- Helps to maintain nutrients in forest soil and minimises erosion and the amount of soil washed away into nearby waterways
Give 2 examples of good forestry practice
1) Planting trees the optimum distance apart - prevents intra-specific competition
2) Controlling pests and diseases - fewer trees need to be felled
What does managed forestry require to make use of the resources without destroying the ecosystem?
Sustainable replanting and regeneration
How are native woodlands preserved and why is this important?
- Replanting native trees
- Allowing native forests to regenerate
- protecting areas of natural woodland
This preserves species and biodiversity
Why are nets with a very small mesh bad?
They catch fish before they have become sexually mature, fewer individuals left to reproduce, population size decreases and genetic diversity decreases
What are the effects of overfishing?
- Depletion of fish stocks (damages the livelihood of fishermen)
- Overfishing krill (primary consumer) which is eaten by many marine animals (whales, penguins, fish) can affect the rest of their food web
