Agricultural Exploitation - Human Impact on Environment

Why is there tension between need to produce food and need to conserve environment and biodiversity

population size is increasing meaning more food is needed

what is agriculture

producing food for human consumption in order to meet demand

how have agriculturalists met demand

made larger fields by removing hedges

cultivated monocultures (single type of crop in a field)

increased use of fertilisers and pesticides

How does hedge removal have a negative impact on the environment and biodiversity

hedges provide habitats

including for pest species and their predators

provide wildlife corridors - allow mobile species to travel to different areas to disperse to find mates

How do monocultures have a negative effect on the environment and biodiversity

allow farmers to grow crops, easily harvestable mechanically and guaranteed to yield disease free seeds

but numbers of a pest species can increase rapidly when they invade a monoculture

monoculture less likely to sustain variety of pests predators which could have kept their numbers under control

pests become out of control

How do fertilisers have negative effects on the environment and biodiversity

cause eutrophication

how do pesticides negatively affect the environment and biodiversity

harm beneficial species and pests

cause them to decline in numbers

can affect the food chain

Why is the rate of deforestation a concern

• happening frequently in tropics

  • woodland clears and burnt using large machinery - compacts ground

What is the effect of succession being unable to occur on compact ground

• leads to soil erosion

• seedlings can’t become established

  • leading to area becoming a desert - process called desertification

What effects can deforestation have

• destruction of habitats and niches

• decrease in biodiversity

• nutrient loss due to increased soil erosion

• succession doesn’t occur as top soil lost

• loss of valuable plant materials - medicine

• contributes to global warming

Sustainable conservation methods for deforestation

• mean that timber can still be extracted without destroying forest

• Succession can happen after trees are removed so they regenerate for future harvesting

• coppicing is traditional method - trees cut into stumps and tree re-grows from stump. long straight stems produced can be harvested

• introduction of protected areas

• replanting of native species within woodlands can help preserve species and promote biodiversity

What are fish stocks

fish populations that are renewable due to births replacing deaths

pops can be harvested indefinitely as a result so fish is a sustainable resource

What is overfishing

level of fishing where increased effort results in a declining catch

too much fishing means that numbers within a population can’t be maintained so fish stocks decline

overfishing can threaten the sustainability of fish populations

How do fishing quotas reduce overfishing impact

• limit amount of members of one species can be caught

  • include heavy fines for exceeding the quotas

how can restricting fishing seasons reduce overfishing impact

banning people from fishing during breeding season allows fish stocks to have time to replesnish population size

how does restricting mesh sizes on nets reduce impact of overfishing

• smaller mesh sizes catch more fish as they catch both large and small

• by increasing mesh size, larger fish will be caught but smaller (usually young) fish will pass through the mesh

• so are able to escape and go on to breed

how do exclusion zones reduce overfishing impact

• completely ban fishing from zones

• fish population will remain at sustainable levels in the exclusion zones

how does fish farming reduce impact of overfishing

• isolating area of sea for the purpose of breeding and growing fish in managed conditions

• animals are fed, treated with chemicals and harvested

What are the negative impacts of fish farming

1. excess nutrients leaking out and causing eutrophication

2. bacteria become resistant due to overuse of antibiotics

3. pesticides can leak out and damage marine food chains

4. overcrowding of fish means that diseases and pests can spread easily

5. genetic modification (for growth rate/size) can harm other populations if they escape and breed or compete for food. to prevent breeding problem many gm fish have 3 sets of chromosomes aka trisomy