Food supply
Increasing food production
- Agricultural machinery to improve efficiency, because they have the ability to farm much larger areas of land.
- Chemical fertilisers -> increase the amount of nutrients in soil → plants grow larger & produce more fruit
- Insecticides & herbicides -> kill off unwanted insects and weed species → less damage done to plants & fruit lost to insects (insecticides) → reducing competition from other plant species (herbicides)
- Selective breeding -> animals and crop plants which produce a large yield are selectively bred to produce breeds that reliably produce high yields.
Large-scale monocultures of crop plants
| Advantages | Disadvantages |
|---|---|
| Ease of management. | Biodiversity is much lower -> increase in pest populations. |
| Reduced Labour and Operational Costs. | Herbicides and pesticides kill plant and insect species that are harmless. |
| High yield. | Continuous use of chemicals causes pests to become resistant to them. |
| Higher revenues from specialised production. |
Intensive livestock production
| Advantages | Disadvantages |
|---|---|
| Increases yield. | Pesticides & insecticides used. |
| More animals can be reared on a small area of field. | Animals are reared in cramped, confined areas -> more infections and diseases. |
| Products are easily available & cheaper. | Cattle generate lots of methane. |
| Urine and faeces can cause eutrophication. |
Habitat destruction
Biodiversity – The number of different species that live in an area
Reasons for habitat destruction
- Increased area for housing, crop plant production & livestock production
- Extraction of natural resources
- Freshwater/marine pollution
Through altering food webs and food chains, humans can have a negative impact on habitats.
Deforestation effects:
- Extinction - Many species are only found in specific areas. Destroyed habitats cause the loss of large number of plants and animals
- Loss of soil - Tree roots help to stabilise the soil. Without trees, nutrients in soil will be washed away into rivers and it’ll be difficult for the trees to regrow.
- Flooding - Without the trees, water is not absorbed by plants and transported into the atmosphere.
- Increased CO2 - Less trees = less photosynthesis -> more CO2 -> global warming
Pollution
Untreated Sewage
- Encourages the growth of bacteria that feed on organic matter -> bacteria uses up lots of oxygen -> freshwater organisms cannot survive.
Excess fertiliser
- Encourage the growth of algae.
- Pesticides concentrated in tissues of some shellfish.
- Radioactive chemicals are found in higher concentrations around coastal nuclear power stations.
- Toxic metals (mercury, copper & lead) found in tissues of marine organisms.
Effects of Non-Biodegradable materials
- Pose threats to aquatic life. Sea turtles swallow plastic bags & get entangled.
- Can cause pollution, block drains
- Harm the animals
Pollutants
- CO2: Sources - burning fossil fuels. Effects - greenhouse effects
- Methane: Sources - cattle/ paddy fields. Effects - greenhouse effects
Eutrophication
- Rain washes fertiliser (nitrate) into the water.
- The water’s mineral content shoots up and algae multiplies very rapidly.
- Algae covers the surface of water, reducing the light reaching the plants at the bottom
- These plants die
- Increased decomposition
- increased aerobic respiration by decomposers caused reduction of dissolved oxygen.
- Death of organisms requiring dissolved oxygen in water (such as fish)
Conservation
Sustainable resource – produced as rapidly as it is removed from the environment so that it does not run out.
Some resources can be conserved and managed sustainably. E.g. forests and fish stocks.
Why organisms become endangered or extinct: climate change, habitat destruction, hunting, overharvesting, pollution, introduced species.
How endangered species can be conserved: monitoring and protecting species and habitats, education, captive breeding programmes, seed banks
How forests can be conserved: educating the population, protecting areas, quotas, replanting
How fish stocks can be conserved: educating the population, closed seasons, protected areas, controlled net types and mesh size so only grown fish are caught, quotas and monitoring.
Reasons for conservation programmes: maintaining or increasing biodiversity, reducing extinction, protecting vulnerable ecosystems, maintaining ecosystem functions.
Artificial insemination (AI), fertilising the egg cell in the vagina through placement of a sperm cell, and in vitro fertilisation (IVF), taking out the egg cell and extelly fertilising it before placing it back into the uterus, are used in captive breeding programmes.