IB Biology SLProtecting BiodiversityPaper 1 & 2Core idea~11 min read
Preserving Biodiversity
There is no single fix, because the problem is not a single problem. Conservation splits into two broad approaches: protect species where they already live, or keep them somewhere safe until they can go back. Both are needed, and both come with awkward decisions about which species get the money.
📚 What you need to know
There is no one solution, so a mixture of approaches is used. Conflicts between human needs and the needs of the natural world make it complicated.
In situ conservation protects species in their natural habitat: protected areas, rewilding, reclamation.
Ex situ conservation protects them away from their habitat: zoos, botanic gardens, seed banks, tissue banks.
Rewilding restores an ecosystem until it can sustain itself. It can be active (intervening) or passive (leaving it alone).
Seed banks store dried seeds in cool, dry, temperature-controlled conditions. Tissue banks store frozen germplasm and somatic tissue.
The EDGE programme, run with the Zoological Society of London, prioritises species that are both Evolutionarily Distinct and Globally Endangered.
NOS: deciding which species to prioritise involves ethical, political, social, cultural and economic issues, so it has to be debated.
The two big approaches
The Latin helps: in situ means “in position”, ex situ means “out of position”. If you can remember that, you will never mix them up.
In situ conservation
Protected areas
A protected area is a defined geographical space that is managed and protected for conservation.
National parks are government-controlled areas where wildlife and the environment are protected.
Nature reserves are usually smaller than national parks, and can be on privately or publicly owned land.
Typical restrictions inside them: human access is strictly controlled, industrial activities such as agriculture and building are tightly regulated, and hunting is limited or banned outright.
Rewilding
Rewilding means restoring an ecosystem to the point where it can sustain itself without ongoing management. A self-sustaining ecosystem is, by its nature, a biodiverse one. It can happen on private or public land, and it comes in two forms.
ACTIVE REWILDING
Humans step in to speed things up.
Removing human features such as roads or drainage
Reintroducing locally extinct species
Bringing in grazing animals to fill a missing role
PASSIVE REWILDING
Humans step back and let it happen.
Stop managing the land and let natural succession take over
Cheaper and needs no expertise
Will not suit every habitat
🤔 Why passive rewilding does not always work
Leaving land alone sounds like the safest option, but it only produces the habitat that succession naturally leads to. Grassland is the classic problem: without grazing animals cropping the vegetation, trees take over and the grassland disappears, along with the species that needed it. Some habitats only exist because something keeps eating them — so protecting a grassland can mean deliberately putting large grazers back, which is active rewilding.
Reclamation
Reclamation is the reclaiming and restoration of areas already damaged by human activity, such as abandoned quarries or land that has been deforested. The aim is to restore the ecosystem that used to be there.
A neat way to separate the three: protected areas defend what is still intact, rewilding rebuilds until nature takes over again, and reclamation repairs ground we already wrecked.
Ex situ conservation
Zoos
Captive breeding programmes increase the number of individuals of a species.
Artificial insemination allows genes to flow between individuals living in different zoos. This avoids the problems of low genetic diversity and gets round the practical difficulties of breeding animals in captivity.
Captive-bred individuals can eventually be released back into the wild.
Zoos are also a research resource: scientists can study genetics, behaviour and habitat requirements up close.
Botanic gardens
The plant equivalent of zoos. They use cuttings and seeds collected from the wild to establish captive populations of endangered plants, and tissue culture and cloning can turn a very small sample into large numbers of plants. Those populations can later be used for reintroduction. Research is a major role too — working out how a species reproduces, grows and what habitat it needs.
Seed banks
A seed bank conserves plant diversity by drying and storing seeds in a temperature-controlled environment.
Cool, dry conditions keep seeds viable for much longer.
Seeds do not last for ever, so after a period they are grown into plants and fresh seed is collected for storage.
If a species goes extinct, the stored seed can be used to grow it again.
Seeds of the same species are collected from different sites, to preserve genetic diversity rather than one population’s alleles.
The Svalbard Global Seed Vault in Norway holds seed from almost a million plant species, in the Arctic where conditions are naturally cold and stable.
Tissue banks
Sometimes called frozen zoos, these store genetic material from animals at very low temperatures. Properly frozen tissue is thought to last indefinitely. As with seed banks, samples are ideally taken from many different individuals to maintain genetic diversity. Two types are stored:
Type
What it is
What it can be used for
Germplasm
Reproductive tissue: sperm cells, egg cells and embryos
Captive breeding in zoos; in theory, IVF with a suitable surrogate species to bring back an extinct species
Somatic tissue
Non-reproductive tissue, i.e. ordinary body cells
Contains the full genome, so it can be used for DNA research and potentially for cloning extinct species in future
Why “different individuals” keeps coming up: every ex situ method faces the same danger. Save one population and you save a fraction of the species’ alleles. Sample widely and you keep the genetic diversity that the species will need if it is ever put back in a changing environment.
Choosing which species to save
There are far more species needing help than there is money to help them, so someone has to prioritise. The EDGE programme, which works with the Zoological Society of London (ZSL), uses two criteria at once.
Priority EDGE species include the largetooth sawfish, the Chinese giant salamander and the purple frog — all strange, all with few close relatives, all in serious trouble.
“Evolutionarily distinct” means the species has few close evolutionary relatives, is unusual in appearance, behaviour and DNA, and represents a part of the evolutionary tree found nowhere else. “Globally endangered” means it is threatened worldwide, using the IUCN red list — not just locally scarce.
The programme’s job is to highlight these species to local, national and international conservation organisations, so they are not lost before anyone even notices they are in trouble.
NOS: prioritising species has to be debated
The EDGE criteria are sensible, but they are not the only things that matter, and this is where science hands over to society.
A species may not be highly threatened itself, but may be essential to an ecosystem that supports other, more threatened species.
A species may be culturally important to a particular nation, which affects how much support conservation gets.
There may be political obstacles — a habitat located in a warzone is extremely hard to protect whatever the science says.
Ethical, social and economic considerations pull in different directions too.
For this reason EDGE does not make the conservation decisions itself. It passes information to stakeholders, so that a range of people can take part in the debate.
Worked examples
WORKED EXAMPLE
Distinguish between in situ and ex situ conservation, giving one example of each. [3]
Step 1: in situConservation of a species within its natural habitat, e.g. a national park or nature reserve.Step 2: ex situConservation of a species away from its natural habitat, e.g. a seed bank or a zoo captive breeding programme.Step 3: the key differenceIn situ preserves the whole ecosystem and its interactions; ex situ preserves only the species itself
WORKED EXAMPLE
Explain why seed banks collect seeds of the same species from several different sites. [2]
Step 1: what different sites give youPopulations in different places have different allele frequencies, so sampling widely captures more alleles.Step 2: why that mattersIt maintains genetic diversity, so a restored population can adapt to and survive environmental changeThe same reasoning applies to tissue banks and to artificial insemination between zoos.
WORKED EXAMPLE
A conservation group must choose between two species. Species A is critically endangered but has many close relatives. Species B is endangered and is the only surviving member of its family. Discuss which the EDGE programme would prioritise. [4]
Step 1: apply the two criteriaEDGE needs a species to be both evolutionarily distinct and globally endangered.Step 2: assess species AHighly endangered, but with many close relatives it is not evolutionarily distinct, so much of its evolutionary history survives elsewhere.Step 3: assess species BEndangered and the last of its family, so it is evolutionarily distinct. Losing it removes a whole branch of the tree of life.Step 4: conclude, then qualifyEDGE would prioritise species B — but the decision is not purely scientificEthical, cultural, political and economic factors are also involved, which is why EDGE informs stakeholders rather than deciding alone.
💡 Exam tip
Know the two lists cold: in situ = protected areas, rewilding, reclamation. Ex situ = zoos, botanic gardens, seed banks, tissue banks.
For rewilding, always split it into active and passive and give an example of each.
Whenever you mention any ex situ method, link it to maintaining genetic diversity. It applies to all of them.
EDGE has two criteria and a species must meet both. Half-answers lose the mark.
For seed banks, say cool, dry and temperature-controlled, and mention that seeds must be regrown periodically.
In NOS answers, name at least two of the competing factors: ethical, environmental, political, social, cultural, economic.
⚠ Common mix-up
Swapping in situ and ex situ. In situ = in position, in the wild. Ex situ = out of position.
Thinking passive rewilding is always best. Grassland taken over by trees is a habitat lost, not restored.
Treating ex situ as the goal. It is a safety net; the aim is to return species to the wild.
Confusing germplasm and somatic tissue. Germplasm is reproductive; somatic is ordinary body cells.
Saying seeds last for ever in a seed bank. They lose viability, so they are grown on and re-collected.
Prioritising by “how endangered” alone. EDGE also needs evolutionary distinctness.
Confusing reclamation with rewilding. Reclamation repairs damaged land; rewilding restores an ecosystem until it sustains itself.
That completes Protecting Biodiversity. Up next: Classification & Cladistics — how all these species get sorted into groups that reflect real evolutionary relationships.
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