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 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').
A protected area works because it conserves a species together with its whole habitat — its food, its shelter, the other species it interacts with and the physical conditions it is adapted to.
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:
- 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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How this is tested: On Paper 3 this topic is asked as a short Outline / Discuss question on the advantages of in situ conservation or on a named strategy such as wildlife corridors.
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.
IB-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.