“Because it is good” will not get you marks. ESS wants five distinct kinds of justification, and it wants you to know how they differ from each other and how they overlap. Learn them as five separate arguments and almost any conservation question becomes straightforward.
📚 What you need to know
There are five kinds of reason for preserving biodiversity: aesthetic, ecological, economic, ethical and social.
Aesthetic: the beauty of nature gives people joy and inspires creativity.
Ecological: species provide ecosystem processes and services, and diversity supports stability and resilience.
Keystone species have a larger effect on an ecosystem than their numbers suggest, so losing them causes knock-on effects.
Economic: ecotourism, natural capital and genetic resources for crops, medicine and biotechnology.
Ethical: species have intrinsic value, and many argue humans have a moral obligation not to cause extinctions.
Social: time in nature improves mental and physical health and brings people together.
The five justifications
The five overlap in practice — a rainforest that draws tourists is also storing carbon and holding undiscovered medicines — but the arguments are logically separate.
Aesthetic reasons
People find real joy and pleasure in the beauty of the natural world.
It inspires human creativity: photography, poetry, music, painting and film.
That value is not measurable in money, which is exactly why it needs stating separately from the economic case.
Ecological reasons
Species and habitats deliver vital ecological processes and services — pollination, water purification, climate regulation and soil fertility.
Biodiversity has a major effect on the stability and resilience of an ecosystem. A more diverse system recovers better from disturbance and adapts better to change.
Take a species-rich lake warming under climate change: some fish cannot cope, but others can or can adapt. Those survive, reproduce and keep contributing, so the ecosystem carries on functioning.
A low-diversity lake has no spare species to take over, so the same warming could shut the system down.
Keystone species
Definition
A keystone species has a much larger effect on the structure and function of its ecosystem than its abundance would suggest. Removing it causes knock-on effects throughout the system.
The counter-intuitive bit: elephants destroy vegetation, and that destruction is what keeps the savannah diverse. Ecologists have recorded major negative impacts where poaching has cut elephant numbers.
Bush elephants graze in an extreme way, knocking over and eating several species of tree.
This prevents any one plant species dominating, creates habitats for other species, and increases biodiversity.
Elephant dung provides habitat for many important fungi and insect species.
Where elephants have been poached for ivory and their numbers greatly reduced, ecologists have observed major negative impacts on the savannah ecosystem.
Do not confuse keystone with abundant. A keystone species is often not numerous at all — that is the whole point. Its importance comes from what it does to the system, not from how much of it there is.
Economic reasons
Economic value
How it works
Example
Ecotourism
Natural areas attract tourists, generating revenue for local economies and providing jobs
Tourists travelling to and spending money in national parks to see wildlife
Natural capital
Ecosystems supply resources such as timber, fish and clean water; maintaining them supports long-term prosperity
A managed forest yielding timber indefinitely rather than once
Genetic resources
Wild species are sources of genes for crop improvement, medicine and biotechnology, which matters for future food security
Crop wild relatives supplying disease resistance to farmed varieties
Medicines
Many drugs used today originated in plants, fungi and bacteria
The cancer drug paclitaxel, sourced from Pacific and Himalayan yew trees
The argument from ignorance, used well. So many drugs have already come from nature that it is reasonable to assume many more are still out there undiscovered. Every species lost is a possibility closed off before anyone has looked. Note the irony in the yew: the Himalayan yew has itself declined through over-harvesting for fuel and medicine.
Ethical reasons
Many people hold that species and habitats have intrinsic value — inherent worth, independent of any usefulness to humans.
Many believe humans have a moral obligation to prevent biodiversity loss caused by human activity.
We share the planet with millions of other species, and a widely held view is that we have no right to cause their extinction.
Because humans are the dominant and most powerful species, many argue that this creates a responsibility to protect the rest.
There is also an obligation to preserve nature for future generations — the intergenerational equity idea from 1.3.
Social reasons
Many people enjoy spending time in the natural environment, doing things together such as birdwatching, walking and climbing.
Access to natural spaces improves mental and physical health.
If biodiversity is not conserved these environments may be lost, and the social benefits they bring are lost with them.
🧠
Easy way to remember the five
Four E’s and an S:Aesthetic, Ecological, Economic, Ethical, Social. Beauty, function, money, morality, wellbeing.
Worked examples
WE 1
Justify preserving biodiversity
Outline four different types of justification for preserving biodiversity, giving an example of each. (4 marks)
Ecological
Species provide ecosystem services such as pollination and water purification, and diversity supports resilience to disturbance.
Economic
Ecotourism generates revenue and jobs, and wild species supply genes for crops and medicines such as paclitaxel from yew trees.
Ethical
Species have intrinsic value and humans have a moral obligation not to cause their extinction.
Social or aesthetic
Access to natural spaces improves mental and physical health, and the beauty of nature inspires human creativity.
Four separate kinds of argument, one example eachdo not give four economic reasons dressed differently — the marks are for the different categories
WE 2
Explain the role of a keystone species
Explain, using a named example, why the loss of a keystone species can reduce biodiversity. (4 marks)
Point 1: the definition
A keystone species has a disproportionate effect on the structure and function of its ecosystem.
Point 2: the example
Bush elephants in the African savannah graze extremely, knocking over and eating several tree species.
Point 3: the mechanism
This prevents any one plant species from dominating and creates a range of habitats; their dung also supports fungi and insects.
Point 4: the loss
Where elephants have been poached and numbers greatly reduced, one or two plant species take over, habitat variety falls and biodiversity declines.
Its effect on the system is what matters, not how many there areexplain the mechanism — naming an example without saying what it does earns one mark at most
WE 3
Compare two justifications
Distinguish between the ethical and economic justifications for conserving a rainforest. (3 marks)
Point 1: economic
Values the forest for what it provides to people — timber, ecotourism revenue, genetic resources and medicines.
Point 2: ethical
Values the forest and its species for their intrinsic worth, independent of usefulness to humans.
Point 3: why it matters
The economic case could justify clearing the forest if something more profitable came along; the ethical case could not.
One asks what it is worth to us; the other says that is the wrong questionthe third point is what turns a definition pair into a real distinction
💡 Exam tips
Learn all five categories and have an example ready for each.
Use the phrase intrinsic value for the ethical case — it is the marking term.
For ecological reasons, link to ecosystem services and resilience.
Know one keystone species properly, with the mechanism, not just the name.
Mention genetic resources and future food security; it is often missed.
Be ready to say how the categories interrelate, not only how they differ.
⚠ Common mistakes
Giving several economic reasons and calling them different types. The categories must actually differ.
Confusing keystone with flagship. Keystone is ecological; flagship is about public appeal.
Saying keystone species are abundant. Often they are not, which is the point.
Treating aesthetic and social as the same. Beauty and inspiration differ from health and recreation.
Leaving out ethics entirely. It is a full category, not a soft add-on.
Vague ecological answers. Name the service: pollination, purification, climate regulation, soil fertility.
Up next: Approaches to Conservation — once you have justified doing something, the next question is which method to use.
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