Human Impact: Biodiversity, Pollution & Conservation

Ensuring Food Supply

• Intensive food production uses modern technology to produce food more efficiently on finite land.
• **Agricultural machinery** enables farming of larger areas, replacing human labour.
• **Chemical fertilisers** increase soil nutrient availability, boosting plant growth and yield.
• **Insecticides** kill pests that damage crops; **herbicides** remove competing weeds.
• **Selective breeding** produces high-yielding crop varieties and livestock breeds.
• Intensive livestock farming reduces energy loss by keeping animals in small spaces, feeding high-energy food, using antibiotics, and maintaining warm temperatures.
• Advantages: less land needed, year-round production, lower costs. Disadvantages: ethical concerns, habitat destruction, reduced biodiversity, methane emissions, water pollution from waste.

Monocultures

• **Monoculture** is growing only one crop species over a large area (e.g., palm oil plantations).
• Advantages: specialised machinery, optimised conditions, higher yields.
• Disadvantages: **reduces biodiversity** – few herbivore species can feed, so few predators survive.
• Pest populations increase due to abundant food; repeated insecticide use leads to **pesticide resistance** and kills non-target insects.

The Importance of Biodiversity

• **Biodiversity** is the number of different species in an area; high biodiversity is needed for stable ecosystems.
• Human activities, especially **habitat destruction**, reduce biodiversity.
• Habitat destruction is driven by the increasing human population needing space for agriculture, housing, and industry.
• Destruction of habitats **interrupts food chains and webs**, causing further species loss.

Deforestation

• **Deforestation** is large-scale clearing of trees, often for cattle grazing, monocultures, or building.
• If trees are replanted, it can be sustainable; otherwise, it causes severe environmental harm.
• Undesirable effects: **extinction of species**, **loss of soil** (erosion), **flooding**, and **increased CO₂** in the atmosphere.

Water Pollution

• Water pollutants include untreated sewage, excess fertilisers, and industrial/agricultural chemicals.
• **Untreated sewage** increases bacteria, which deplete oxygen, killing aquatic life (eutrophication).
• **Excess fertiliser** runoff causes **algal blooms** that block sunlight; plants die, decomposers use up oxygen, leading to fish kills.
• Other sources: oil spills, toxic chemicals from industry, and plastic waste.

Other Pollution

• **Plastic pollution**: non-biodegradable; animals ingest or become entangled; toxins enter food chains; on land, landfills release toxins into soil.
• **Air pollution**: **methane** (from cattle, rice paddies, landfills) and **carbon dioxide** (from burning fossil fuels/deforestation) are greenhouse gases.
• Increased greenhouse gases cause **global warming** and **climate change**; melting permafrost releases more methane.

Sustainability

• A **sustainable resource** is produced as fast as it is used, so it does not run out.
• **Fossil fuels** are non-renewable; we must reduce use and find alternatives.
• **Recycling** paper, plastic, glass, and metal reduces waste and raw material demand.
• **Sustainable forestry**: replant trees, use certification schemes (e.g., Forestry Stewardship Council), educate consumers.
• **Sustainable fishing**: quotas, size limits, seasonal bans, restocking, and consumer education.

Endangered Species & Conservation

• An **endangered species** is at risk of extinction due to hunting, climate change, pollution, habitat loss, or invasive species.
• Conservation measures: **education programmes**, **captive breeding**, **legal protection** of species and habitats, **seed banks** for plants.
• **Captive breeding** can use **artificial insemination (AI)** to transport sperm between zoos, and **in vitro fertilisation (IVF)** to maintain genetic diversity.
• Low genetic variation makes a species more vulnerable to environmental change and extinction.

Reasons for Conservation

• Conservation maintains **biodiversity** for stable ecosystems, reduces extinction, and protects vulnerable habitats.
• It maintains ecosystem functions like **nutrient cycling** (e.g., carbon cycle).
• Provides resources: **food**, **drugs** (plant-based remedies), **fuel**, and **genes** for wide gene pools.
• Moral, cultural, and scientific reasons: preserving species for future generations and potential discoveries.

Eutrophication process showing fertiliser runoff leading to algal bloom, plant death, and fish kill.

Energy pyramid showing trophic levels and energy loss.

Sustainable fishing methods to maintain fish stocks.