The big idea: In situ conservation means protecting a species in its natural habitat — leaving it where it lives instead of moving it to a zoo or a seed bank.
The main tool: The main tool is a protected area (a nature reserve or national park) where the whole ecosystem is kept intact, so the species and everything it depends on are conserved together.
In situ — in the natural place
- Species protected in its own habitat
- Examples: nature reserves, national parks, wildlife corridors
- The whole ecosystem is conserved together
- Species keep behaving and evolving naturally
Ex situ — away from the natural place
- Species protected outside its habitat
- Examples: zoos, botanic gardens, seed/gene banks
- Only the species (not its ecosystem) is kept
- Used as a backup when in situ is not enough
Latin tip: 'In situ' literally means 'in place'. If the organism stays in its natural home, it is in situ. If it is taken somewhere else (a zoo, a seed bank), it is ex situ ('out of place').
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A protected area works because it conserves a species together with its whole habitat.
What the habitat keeps for it
- Its food and its shelter
- The other species it interacts with
- The physical conditions it is adapted to
Why that matters: Because nothing is removed from the wild, the population stays large enough to keep its genetic diversity, and the species carries on behaving, breeding and evolving naturally.
- In situ conservation
- Protecting a species within its natural habitat.
- Protected area
- A region of habitat (e.g. a nature reserve or national park) managed to conserve the species living there.
- Wildlife corridor
- A protected strip of habitat that connects two separate reserves so animals can move between them.
- Habitat fragmentation
- The breaking up of one large habitat into smaller, separated patches.
- Edge effect
- Conditions near the boundary of a habitat patch (wind, light, predators, intruding species) that differ from the sheltered interior.
Reserve design matters: How a reserve is shaped and connected changes how well it works.
Three design rules
- A larger, rounder reserve has more sheltered interior and less exposed edge, so it protects more species.
- A long, thin reserve is almost all edge, so harsh edge conditions reach every part of it.
- Wildlife corridors join separate reserves so animals can move, mate and recolonise — reducing the harm of fragmentation.
| Reserve shape | Interior (core) habitat | Effect on species |
|---|---|---|
| Large and round | lots of sheltered interior | protects the most species |
| Small and round | some interior | protects fewer species |
| Long and thin | almost no interior — nearly all edge | protects the fewest species |
Why edge is bad: Near the edge of a habitat patch it is windier, brighter and drier, predators get in more easily and invasive species spread inward. Many native species can only survive in the sheltered interior, so a reserve with more interior and less edge conserves more of them.
Three reserve-design ideas. A large, rounded reserve has a big sheltered core and only a thin edge (protects the most species). A long, thin strip of the same area is almost all edge with no core (protects the fewest). Two reserves joined by a wildlife corridor let animals move between them and interbreed.
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The big idea: Ex situ conservation means protecting a species away from its natural habitat — for example in a zoo, a botanic garden or a seed bank.
When in situ is not enough: Protecting the habitat is not always enough. When a wild population is tiny or its habitat badly damaged, the species is also kept safe away from home: no single approach is enough, and different species need different measures.
A back-up plan: It is a back-up plan: it keeps a species alive when its wild habitat is too damaged, too small or too dangerous for it to survive there right now.
- Ex situ conservation
- Protecting a species OUTSIDE its natural habitat — e.g. in a zoo, botanic garden, captive-breeding centre, seed bank or gene bank.
- In situ conservation
- Protecting a species INSIDE its natural habitat — e.g. by setting up a nature reserve or national park.
- Captive breeding
- Breeding endangered animals under human care to raise their numbers, often aiming to release them back into the wild.
- Seed bank
- A store where seeds from many plant species are kept cold and dry so they stay alive for decades as a back-up.
Two words to keep straight: In situ = IN the habitat (in the wild).
Ex situ = EX-ternal to the habitat (off-site, e.g. a zoo).
If the protected animals or seeds are not in the wild, the method is ex situ.
The two approaches side by side. In situ (left) protects the species in its natural habitat — a nature reserve — keeping the whole ecosystem and natural behaviour. Ex situ (right) protects it off-site in a zoo, seed bank or gene bank as a back-up. The reintroduction arrow shows ex situ feeding individuals back to the wild — the two work best together.
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Ex situ conservation does not just store a species — it actively tries to increase its numbers and keep its genes safe so the species can one day return to the wild.
It does this in a few main ways:
| Method | What it does | Example use |
|---|---|---|
| Captive breeding (zoos) | Breeds animals safely, away from predators and poachers, to raise numbers | Building up a small population of a rare big cat |
| Botanic gardens | Grow and protect rare plants, and study how to germinate them | Keeping rare orchids alive and propagating them |
| Seed banks | Store many seeds, cold and dry, as a long-term genetic back-up | Saving thousands of crop and wild-plant varieties |
| Gene / tissue banks | Freeze cells, sperm or eggs to preserve a species' genetic variety | Keeping frozen samples of a critically endangered frog |
Why this helps an endangered species
- Animals breed safely — away from predators, poachers and disease
- Numbers can be raised quickly under expert care, then individuals reintroduced to the wild
- Genetic variety is preserved (studbooks and gene banks avoid too much inbreeding)
- It is a safety net: the species survives even if its wild habitat is destroyed
- Captive populations support research and public education, raising funds and support
Why it is only a back-up: Ex situ conservation has real limits.
Its limits
- It is expensive and can only hold small numbers, so genetic variety may still be lost over time (inbreeding).
- Animals raised in captivity may struggle to survive when released.
- Crucially, the species' natural habitat is not protected.
- So ex situ work is best used alongside in situ conservation, not instead of it.
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The big idea: Where a habitat is already badly damaged, a third approach is needed. Rewilding means helping a damaged ecosystem repair itself by putting back the natural processes that used to run it — and then stepping back to let nature take over.
The aim and the tool
- Instead of managing every detail forever, the aim is a self-sustaining ecosystem that looks after itself.
- The headline tool is bringing back a keystone species — a species whose activity shapes the whole community.
Ordinary conservation
- Protects species as they are now
- Often needs ongoing human management
- Aims to stop further loss
Rewilding / restoration
- Restores lost natural processes
- Aims for a self-sustaining ecosystem
- Aims to reverse damage and let nature run it
Two words to be sure of: Keystone species — a species that has a very large effect on its ecosystem relative to its numbers (for example a top predator or a beaver).
Degraded ecosystem — an ecosystem that has been damaged so that it works less well (for example a cleared forest or a drained wetland).
Rewilding works by restoring natural processes — the things that healthy ecosystems do on their own, such as grazing, predation, flooding and seed dispersal.
Once these processes are running again, the ecosystem can maintain itself without constant human input.
- Rewilding
- Restoring natural processes to a degraded ecosystem so it becomes self-sustaining, often by reintroducing a keystone species.
- Reintroduction
- Releasing a species back into an area where it used to live but had died out locally.
- Ecosystem restoration
- Repairing a damaged ecosystem so its natural processes and biodiversity recover.
- Natural process
- A self-running ecosystem activity such as grazing, predation, flooding or seed dispersal.
| Rewilding method | What it does | Example process restored |
|---|---|---|
| Reintroduce a keystone species | Puts back a species whose activity shapes the community | predation / dam-building |
| Re-establish natural grazing | Lets large herbivores keep vegetation open and varied | grazing |
| Restore natural water flow | Removes drainage or dams so wetlands and rivers behave naturally | flooding |
| Remove human controls | Stops fences, culling or planting so the system self-regulates | self-regulation |
| Replant / let native plants return | Rebuilds the plant community that supports everything else | seed dispersal |
| Reconnect habitats (corridors) | Lets species move and spread between patches | dispersal / gene flow |
The keystone idea: A keystone species has an effect far bigger than its numbers. That is why reintroducing one keystone species can restart a chain of natural processes across the ecosystem.
Two examples
- Bring beavers back and they build dams → wetlands form → many other species return.
- Bring a top predator back and it controls grazers → plants recover → the whole food web shifts.
Reintroducing a keystone species sets off a cascade that restores biodiversity.
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How this is tested: On Paper 1A you may be asked which action is in situ, or which is part of rewilding. On Paper 2 it is an Outline, Explain or Discuss question on in situ, ex situ or rewilding methods, often for a named species.
Data-style questions: Data-style questions can give you a diagram of reserve shapes and ask you to Predict which shape protects the most species — and to justify it using the edge effect.
Exam-style question — wildlife corridors
A national park is split into two reserves by a new motorway. Conservationists build a forested bridge — a wildlife corridor — linking the two reserves. Outline how this corridor helps preserve biodiversity. [3]
How to score all three marks
- Movement between reserves. The corridor lets animals move between the two reserves instead of being trapped in one fragment.
- Mixing of populations. Animals from the two sides can interbreed, which increases genetic diversity and avoids inbreeding in a small isolated population.
- Recolonisation and resources. Animals can recolonise an area after a local loss and reach more food, mates and habitat — so populations are larger and more stable.
- Answer the command term (Outline): the corridor reconnects the fragments so animals can move, interbreed and recolonise, keeping populations larger and genetically diverse.
Final answer
The corridor reconnects the two fragments so animals can move between them, interbreed to keep genetic diversity high, and recolonise after local losses — keeping populations larger and more stable.
Marking note: Three distinct points score here: (1) animals can move between reserves, (2) populations interbreed / keep genetic diversity, (3) animals can recolonise / reach more resources. Three separate ideas — not the same point worded three times.