IGCSEBiologyCambridge (CIE)Revision Notes20. Human Influences on EcosystemsHuman Impact: Biodiversity, Pollution & ConservationThe Importance of Biodiversity

The Importance of Biodiversity (Cambridge (CIE) IGCSE Biology): Revision Note

Exam code: 0610 & 0970

Written by: Phil

Reviewed by: Jenna Quinn

Updated on 31 August 2026

Human pressures on other species

Biodiversity

Biodiversity is defined as the number of different species that live in a particular area
Human activities have tended to force biodiversity downwards, whereas high biodiversity is needed for stable ecosystems
Habitat destruction by humans is a major downward pressure on biodiversity

Reasons for habitat destruction

The increasing human population of the planet is causing destruction of many habitats from rainforest to woodland to marine
Many habitats are destroyed by humans to make space for other economic activities, or by pollution from these activities, and this reduces the biodiversity of these areas
This interrupts food chains and webs, meaning that more species may die because their prey is gone
The main reasons for habitat destruction are outlined in the table below

Reason	Explanation
Clearing land for farming and housing	Crops, livestock and homes all take up a large amount of space As there is an increasing population and demand for food, the amount of land available for these things must be increased by clearing habitats such as forests (deforestation)
Extraction of natural resources	Natural resources such as wood, stone and metals must be gathered to make different products Therefore many trees are cut down, destroying forest habitats. In addition, some resource extraction takes up a large amount of space For example: mining, which means that the land must be cleared first
Marine pollution	Human activities lead to the pollution of marine habitats In many places, oil spills and other waste pollutes the oceans, killing sea life In addition, eutrophication can occur when fertilisers from intensively farmed fields enters waterways This causes a huge decrease in biodiversity in these areas as most aquatic species living in these waterways die from lack of oxygen

Deforestation

Deforestation is the clearing of trees (usually on a large scale)
If trees are replaced by replanting it can be a sustainable practice (opens in a new tab)
Generally the trees are being cleared for the land to be used in a different way (for building, grazing for cattle, planting of monocultures such as palm oil plantations etc) and therefore it is not sustainable
As the amount of the Earth’s surface covered by trees decreases, it causes increasingly negative effects on the environment and is a particularly severe example of habitat destruction
Undesirable effects of deforestation include:
- extinction of species
- loss of soil
- flooding
- increase of carbon dioxide in the atmosphere

Effect	Consequence
Extinction / loss of biodiversity	Forest habitats, especially tropical rainforests, have a huge range of biodiversity and as habitat is destroyed it causes the loss of large numbers of plant and animal species Many of these species are only found in these areas and therefore will become extinct
Soil erosion	Tree roots help to stabilise the soil, preventing it from being eroded by rain Trees will usually take up nutrients and minerals from the soil through their roots Without trees, nutrients and minerals will remain unused in the soil so will be washed away into rivers and lakes by rain (leaching) This loss of soil nutrients is permanent and makes it very difficult for forest trees to regrow, even if the land is not cultivated with crop plants or grass for cattle
Flooding	Without trees the topsoil will be loose and unstable so will be easily washed away by rain, increasing the risk of flash flooding and landslides
Increased carbon dioxide in atmosphere	Trees carry out photosynthesis during which they take in carbon dioxide and release oxygen The removal of significant numbers of trees means less carbon dioxide is being removed from the atmosphere (and less oxygen released) When areas of land in forests are cleared for land use, the trees are often burned as opposed to being cut down. This releases carbon dioxide (it is an example of combustion), further increasing carbon dioxide levels in the atmosphere and contributing to global warming

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

I would just like to say a massive thank you for putting together such a brilliant, easy to use website.I really think using this site helped me secure my top gradesin science and maths. You really did save my exams! Thank you.

Beth
IGCSE Student

This website is soooo useful and I can’t ever thank you enough for organising questions by topic like this. Furthermore, the name of the website could not have been more appropriate as it literally did SAVE MY EXAMS!

Fathima
A Level Student

Incredible! SO worth my money, the revision notes have everything I need to know and are so easy to understand. I actually enjoy revising! It makes me feel a lot more confident for my GCSEs in a few months.

Kate
GCSE Student

Absolutely brilliant, both my girls used it for A levels and GCSE. It's saves on paper copies, also beneficial exam questions ranked from easy to hard. It's removed a lot of stress from the exams.

Sameera
Parent

Just to say that your resources are the best I have seen and I have been teaching chemistry at different levels for about 40 years

Mark
Chemistry Teacher

Excellent