Human Impact: Biodiversity, Pollution & Conservation
Cambridge IGCSE Biology — Complete Revision Guide
The Big Idea: Human activities like intensive farming, habitat destruction, and pollution reduce biodiversity and damage ecosystems. However, we can conserve endangered species and manage resources sustainably through education, breeding programmes, monitoring, and international cooperation.
Quick Summary
This chapter covers six interconnected topics:
- Ensuring Food Supply: Intensive farming, monocultures, livestock farming — how we produce more food but at what cost?
- Biodiversity & Habitat Loss: Why habitat destruction is the biggest threat to species, and how deforestation causes cascading problems.
- Pollution: Water (eutrophication), air (CO₂ and methane, greenhouse effect), and plastic pollution.
- Sustainability: Using resources at the rate they're produced, with examples of forest and fish stock management.
- Endangered Species: Why species become endangered, what conservation methods exist, and why we need to protect them.
- Conservation Techniques: Education, captive breeding (including AI and IVF), monitoring, seed banks.
Ensuring Food Supply: Intensive Farming
What Is Intensive Food Production?
Intensive farming means producing more food from the same amount of land using modern technology and methods. As the global population grows, we need more food, so we've developed four key techniques:
Intensive Food Production
Using advanced technology and inputs (machinery, fertilisers, pesticides, selective breeding) to maximise yield from a fixed area of land.
Four Keys to Intensive Crop Production
1. Agricultural Machinery
Tractors and harvesting equipment replaced humans, allowing farmers to work much larger areas and do it faster. Less labour cost, more land farmed.
2. Chemical Fertilisers
Added to soil to increase available nitrogen, phosphorus, and potassium — nutrients plants need to grow. Result: bigger plants, more fruit, higher yields. But fertiliser runoff pollutes waterways (more on this later).
3. Insecticides & Herbicides
Kill pests (insects) that damage crops and weeds that compete with crops for resources. Less damage = more surviving plants = higher yield. But they also kill harmless insects and pollute the environment.
4. Selective Breeding
Farmers choose animals and plants with desirable traits (high milk yield, fast growth, large fruit) and breed them together. Over generations, you get varieties that reliably produce high yields — but often with reduced genetic diversity.
Intensive Livestock Farming
Keeping animals in small, confined spaces increases energy efficiency. Animals spend less energy on movement, regulating temperature, and roaming — all that energy goes into growth instead.
Energy flow in intensive livestock:
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Feed → [Animal in confined space] → Less movement
↓
Less energy wasted on:
• Walking/roaming
• Thermoregulation (kept warm)
↓
More energy → GROWTH & MEAT PRODUCTION
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Other tricks:
- Feed animals high-energy foods → more energy per unit of food digested
- Keep them in artificially warm environments → less energy spent on heating their bodies
Advantages of Intensive Livestock Farming