Chapter 20: Human influences on ecosystems (Part 1)

01 Increasing food production

Technological advancements have allowed humans to maximise crop and livestock yields to meet the demands of a growing population.

Agricultural machinery

Used instead of manual labour to farm larger areas of land more quickly and efficiently.

Chemical fertilisers

Increase available nutrients in the soil, allowing plants to grow larger and produce more fruit.

Insecticides and herbicides

Chemicals used to kill pests and weeds, reducing crop damage and competition for resources.

Selective breeding

Breeding organisms with desirable features over generations to improve the yield and quality of crops and livestock.

02 Farming practices: monocultures and intensive production

Monocultures

Growing only one species of crop in a large area to maximise efficiency.

Disadvantages of monocultures

Leads to a significant loss of biodiversity, which can harm food webs and reduce the populations of various species.

Intensive livestock production

Keeping animals in high densities while restricting movement and maintaining optimum temperatures to limit energy loss.

Disadvantages of intensive livestock production

Not sustainable; livestock produce large amounts of methane (a greenhouse gas), and high amounts of antibiotics are required to prevent disease.

03 Habitat destruction

Biodiversity

Defined as the number of different species living in a particular area.

Reasons for destruction

Habitats are cleared to make space for housing, farming (crops and livestock), and the extraction of natural resources like wood, stone, or minerals.

Impact

Pollution and the clearing of land interrupt food chains and webs, leading to a decrease in biodiversity and the potential death of species whose prey has disappeared.

04 Undesirable effects of deforestation

Deforestation is a primary example of habitat destruction with several critical consequences:

1. Extinction: Loss of habitat leads to the permanent loss of species.
2. Loss of biodiversity: Fewer species can survive in the altered environment.
3. Soil erosion: Without roots to anchor the soil, it is washed away by rain or blown by wind, decreasing fertility.
4. Flooding: Lack of trees increases flash flooding because water is no longer slowed or absorbed as effectively by the forest.
5. Increased atmospheric CO₂: Fewer trees mean less carbon dioxide is removed via photosynthesis, contributing to global warming.