Why biodiversity is being lost
Big idea: Biodiversity loss happens mainly because of human activities. When ecosystems are damaged, both nature and human societies are affected.
A real example: Gorillas under threat
Gorillas once lived safely in large rainforest areas. Today, their numbers have dropped sharply and they are now critically endangered.
- Forests are cleared for towns, farms, and mining
- Gorillas lose food and living space
- Some are hunted or captured illegally
- Small populations struggle to recover
When habitats shrink, species struggle to survive.
Direct threats to biodiversity
Some human actions directly target species or remove resources from ecosystems.
- Overharvesting – removing too many fish, trees, or plants
- Poaching – illegal hunting for valuable animal parts
- Illegal pet trade – capturing wild animals to sell as pets
Direct threats usually affect one species first, then spread through food webs.
Indirect threats to biodiversity
Other human activities damage ecosystems as a side effect, even when species are not the main target.
- Habitat loss from deforestation, farming, and urban growth
- Climate change altering temperature and rainfall patterns
- Pollution of air, soil, and water
- Invasive species introduced by humans
Indirect threats usually affect many species at once.
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Invasive species: why they are dangerous
Invasive species are organisms moved by humans into new ecosystems where they do not belong.
- They compete strongly for food, water, and space
- Some are predators with no natural enemies
- They may bring new diseases or parasites
- Native species often decline quickly
Example: In parts of the USA, invasive snakes reduced native animal populations by eating prey faster than ecosystems could replace them.
What is the tragedy of the commons?
The tragedy of the commons happens when shared resources are overused because no one takes responsibility for protecting them.
- Everyone benefits from using the resource
- Individuals focus on short-term gain
- The resource becomes depleted
- Long-term damage affects everyone
If everyone takes a little too much, the whole system collapses.
Why management matters
Biodiversity loss is not just about sharing resources — it is about how they are managed.
- Unmanaged resources are often overused
- Pollution increases without regulation
- Ecosystems lose resilience
- Well-managed systems can remain sustainable
When impacts combine
Ecosystems are often hit by several pressures at the same time.
- Climate change + pollution
- Habitat loss + invasive species
- Overharvesting + disease
Multiple stresses reduce resilience and increase the risk of ecosystem collapse.