Conservation

1. Overview

Conservation is the active protection and management of species and habitats so that biodiversity is maintained. Many populations are declining or have already become extinct, driven by climate change, competition, hunting by humans and the degradation and loss of habitats.

Conservationists respond in two ways: in situ methods protect species in their natural habitat (such as national parks and marine parks), while ex situ methods protect species away from their habitat (such as zoos, botanic gardens, frozen zoos and seed banks). For endangered mammals, assisted reproduction (IVF, embryo transfer and surrogacy) can raise numbers, while the spread of invasive alien species must be controlled. International cooperation is led by the IUCN, which assesses species, and CITES, which regulates trade.

Key Definitions

• Conservation: the protection, management and, where needed, restoration of species and habitats so that biodiversity is maintained for the future.
• Biodiversity: the variety of life, measured as the number and relative abundance of species, the genetic variation within species, and the range of ecosystems present.
• Endangered species: a species at high risk of extinction in the wild in the near future unless action is taken.
• In situ conservation: conserving species in their natural habitat, for example within national parks, marine parks and protected reserves.
• Ex situ conservation: conserving species away from their natural habitat, for example in zoos, botanic gardens, frozen zoos and seed banks.
• Frozen zoo: a store of frozen genetic material such as eggs, sperm, embryos and tissue kept at very low temperatures for future breeding.
• Invasive alien species: a non-native species, introduced by humans, that spreads and harms native species, habitats or the economy.
• IUCN: the International Union for Conservation of Nature, which assesses species and publishes the Red List of Threatened Species.
• CITES: the Convention on International Trade in Endangered Species, an agreement between countries that regulates and restricts the international trade in threatened species.

Content

Why populations and species become extinct

A species becomes extinct when its last individual dies, so it no longer exists anywhere. A population (the members of a species in one area) can disappear locally even while the species survives elsewhere. Four main causes are tested at A-Level.

• Climate change: rising temperatures, altered rainfall and rising sea levels shift conditions faster than many species can adapt or migrate. If a habitat warms beyond a species' tolerance, or a food source disappears, numbers fall. Specialists with narrow tolerance ranges (for example polar species dependent on sea ice) are most vulnerable.
• Competition: when two species need the same limited resource (food, light, nesting sites), the stronger competitor reduces the resources available to the weaker one. The weaker species reproduces less and its population shrinks, sometimes to extinction. This is often severe when a new competitor is introduced.
• Hunting by humans: overharvesting for food, trophies, fur, ivory or traditional medicine can remove individuals faster than the population can replace them. If the death rate exceeds the birth rate for long enough, the population cannot recover.
• Degradation and loss of habitats: clearing forests for farming, draining wetlands, mining and pollution destroy or fragment habitats. Fragmentation splits populations into small, isolated groups that have less genetic variation, breed less successfully and are more easily wiped out by disease or chance events.

Reasons to maintain biodiversity

There are several distinct arguments for conserving biodiversity, and a strong answer gives reasons from more than one category.

• Ecological: species are interdependent within food webs and nutrient cycles. Removing one species can have knock-on effects (for example loss of a pollinator reduces plant reproduction), reducing ecosystem stability.
• Economic: wild species provide food, timber, fibres and tourism income (ecotourism). A diverse gene pool in wild relatives of crops can be bred into cultivated varieties to improve yield or disease resistance, for example crossing a disease-resistance allele from a wild relative of wheat into a cultivated variety to protect harvests.
• Medical and scientific: many medicines are derived from wild organisms, and undiscovered species may hold future drugs. Biodiversity is also a source of scientific knowledge.
• Genetic: maintaining large, varied populations preserves genetic diversity (a large gene pool), which allows species to adapt to future change such as new diseases or a changing climate.
• Ethical and aesthetic: many people argue species have a right to exist and that future generations should be able to enjoy them.

Roles of zoos, botanic gardens, conserved areas, frozen zoos and seed banks

Conservation methods are either in situ (in the natural habitat) or ex situ (away from it).

• National parks and marine parks (in situ): large protected areas where habitats and their species are managed together. Activities such as hunting, building and pollution are restricted. Keeping species in their natural environment means they continue to evolve in response to natural selection and whole ecosystems are preserved, but it is harder to protect them from poaching and habitat change.
• Conserved areas / reserves (in situ): smaller protected habitats, sometimes linked by wildlife corridors that connect fragmented areas so animals can move and gene flow continues.
• Zoos (ex situ): keep and breed endangered animals in captivity, often using captive breeding programmes and studbooks to avoid inbreeding. Bred individuals may later be reintroduced to the wild. Zoos also support research and public education.
• Botanic gardens (ex situ): grow and propagate endangered plants, maintain living collections and supply material for reintroduction and research.
• Frozen zoos (ex situ): store frozen gametes (eggs and sperm), embryos and tissue samples in liquid nitrogen. This preserves genetic material from many individuals in a very small space and can be used in future breeding, helping to maintain genetic diversity.
• Seed banks (ex situ): store dried, cooled seeds from many plant species. Seeds take up little space, remain viable for long periods, and provide a backup if wild plants are lost; samples are tested periodically and grown to renew stocks.

Each approach has clear strengths and weaknesses, summarised below.

Feature	In situ (in the habitat)	Ex situ (away from the habitat)
Examples	National parks, marine parks, reserves	Zoos, botanic gardens, frozen zoos, seed banks
Ecosystem	Whole ecosystem and natural interactions preserved	Only the chosen species kept; ecosystem not preserved
Evolution	Species keep adapting through natural selection	Risk of adapting to captivity, making reintroduction harder
Population size	Can support large, naturally varied populations	Usually small populations; risk of losing genetic variation
Main weakness	Hard to protect from poaching and habitat change	Costly; small gene pool; depends on later reintroduction
Best used when	Habitat still intact and large enough	Habitat too damaged or species too rare to survive in the wild

Assisted reproduction in endangered mammals

When wild populations are very small or breed poorly, assisted reproduction can increase offspring numbers and spread genetic material between separated populations. At A-Level this is limited to three techniques.

• IVF (in vitro fertilisation): eggs are collected from a female and fertilised by sperm outside the body in laboratory conditions. The resulting embryos can be implanted or frozen for later use.
• Embryo transfer: an early embryo (produced by IVF or flushed from a donor) is transferred into the uterus of a female so that it implants and develops. One genetically valuable female can supply several embryos.
• Surrogacy: the transferred embryo is carried by a surrogate mother, which may be a female of the same species or a closely related species, allowing offspring to be produced even when the genetic mother cannot carry a pregnancy.

Together these methods raise birth rates, allow valuable genes (including those stored in a frozen zoo) to be used, and help maintain genetic diversity in small populations.

Controlling invasive alien species

An invasive alien species is a non-native species, usually introduced by human activity, that establishes and spreads. It must be controlled because it can:

• outcompete native species for food, light or space, reducing their numbers;
• prey on native species that have no defences against the new predator;
• introduce new diseases or parasites to which native species have no resistance;
• breed with native species (hybridise), diluting the native gene pool;
• alter the habitat (for example by changing nutrient levels or shading), making it unsuitable for native species.

The overall effect is a loss of native biodiversity and, often, economic damage to farming or fisheries, so invasive species are controlled by removal, biological control or preventing their introduction in the first place.

Roles of the IUCN and CITES

International conservation needs cooperation between countries, coordinated mainly by two organisations.

• IUCN (International Union for Conservation of Nature): a global organisation that assesses and categorises species according to their risk of extinction and publishes this information as the Red List of Threatened Species (with categories such as Least Concern, Vulnerable, Endangered and Critically Endangered). The IUCN gathers data, advises on conservation priorities and helps set up protected areas; it does not itself ban or police trade.
• CITES (Convention on International Trade in Endangered Species): an international agreement between governments that regulates and restricts the international trade in threatened species and products made from them (such as ivory and rare plants). Trade in the most threatened species is banned, while trade in others is allowed only with permits, removing the financial incentive to overharvest them.

Worked example

Exam-style question: A small island has a population of a flightless native bird that nests on the ground. Rats arrive on a cargo ship and eat the birds' eggs, and the bird population begins to fall. Conservationists collect some eggs and rear the chicks in a captive breeding centre. Using this example, explain why the rats threaten the birds and outline one in situ and one ex situ measure that could conserve the birds. [5]

Model answer:

• The rats are an invasive alien species introduced by humans; they prey on the eggs, against which the ground-nesting birds have no defence, so the death rate of offspring rises and the bird population falls.
• With low breeding success and a small, isolated population, the birds risk extinction and loss of genetic variation.
• In situ measure: protect the birds in their natural habitat by removing or controlling the rats within a fenced reserve / protected area, so eggs survive and the population can recover where it naturally lives.
• Ex situ measure: run a captive breeding programme (a zoo-type centre) to rear chicks safely, using a studbook to maintain genetic diversity.
• Once the rats are controlled, the captive-bred birds can be reintroduced to the wild to rebuild the population.

Worked example

Exam-style question: Two woodlands were surveyed for ground beetles. The numbers of individuals of each species are shown below. Calculate Simpson's Index of Diversity ($D$) for woodland A, and state, with a reason, which woodland has the greater biodiversity. [4]

Species	Woodland A (n)	Woodland B (n)
Species 1	10	24
Species 2	8	3
Species 3	6	2
Species 4	1	1
Total (N)	25	30

Model answer:

• Use $D = 1 - \sum \left(\dfrac{n}{N}\right)^2$ with $N = 25$ for woodland A.
• Work out each $\left(\dfrac{n}{N}\right)^2$, keeping full decimals: $\left(\tfrac{10}{25}\right)^2 = 0.16$, $\left(\tfrac{8}{25}\right)^2 = 0.1024$, $\left(\tfrac{6}{25}\right)^2 = 0.0576$, $\left(\tfrac{1}{25}\right)^2 = 0.0016$.
• Sum the values: $0.16 + 0.1024 + 0.0576 + 0.0016 = 0.3216$.
• Subtract from 1: $D = 1 - 0.3216 = 0.678$ (to 3 significant figures).
• Work woodland B the same way, with $N = 30$ and full decimals: $\left(\tfrac{24}{30}\right)^2 = 0.64$, $\left(\tfrac{3}{30}\right)^2 = 0.01$, $\left(\tfrac{2}{30}\right)^2 = 0.004\overline{4}$, $\left(\tfrac{1}{30}\right)^2 = 0.001\overline{1}$, which sum to $0.6556$, so $D = 1 - 0.6556 = 0.344$ (to 3 significant figures). One species dominates (24 of 30), so the sum of squares is large and $D$ is lower.
• Woodland A has the greater biodiversity because it has a higher value of $D$: its individuals are spread more evenly across the four species, whereas woodland B is dominated by a single species.

Key Equations

This topic is mainly qualitative. Where biodiversity is measured quantitatively, Simpson's Index of Diversity is used: $$D = 1 - \sum \left(\frac{n}{N}\right)^2$$ where $n$ is the number of individuals of one species and $N$ is the total number of individuals of all species. The value of $D$ lies between 0 and 1, and a higher value indicates greater biodiversity (more species and a more even spread of individuals).

Common Mistakes to Avoid

• Rounding too early in a Simpson's Index calculation. Keep the full number of decimal places on your calculator through every intermediate step and round only the final value (for example to three significant figures), otherwise small rounding errors build up and lose marks.
• Confusing the roles of the IUCN and CITES. The IUCN assesses species and publishes the Red List; it does not control trade. CITES regulates international trade between countries. Stating that the IUCN bans trade is a common error.
• Confusing in situ and ex situ. "In situ" means in the natural habitat (national parks, marine parks, reserves); "ex situ" means away from it (zoos, botanic gardens, frozen zoos, seed banks). Sort each example correctly before writing.
• Giving only one type of reason for maintaining biodiversity. A question asking for reasons usually expects more than one category, so draw on ecological, economic, genetic and ethical arguments rather than repeating the same idea.
• Vague answers on invasive species. Do not just say they are "bad". State a precise mechanism, for example that they outcompete, prey on, or spread disease to native species, reducing native biodiversity.
• Muddling the assisted-reproduction techniques. Be exact: IVF is fertilisation outside the body, embryo transfer places an embryo into a female's uterus, and surrogacy uses another (sometimes related) female to carry the pregnancy.

Exam Tips

• For "explain extinction" questions, name a specific cause (climate change, competition, hunting, habitat loss) and link it to the population, for example "death rate exceeds birth rate" or "loss of genetic variation in fragmented populations".
• Label each conservation method clearly as in situ or ex situ to make the distinction clear.
• For a "compare" or "discuss" question on in situ versus ex situ, pair each point in a single linked sentence (for example, "in situ preserves the whole ecosystem whereas ex situ keeps only the chosen species"); comparison marks need an explicit contrast, not two separate lists.
• When asked about reasons to maintain biodiversity, write reasons from different categories (ecological, economic, genetic, ethical) to access the full range of marks.
• Keep the IUCN (assess and list) versus CITES (regulate trade) difference firmly fixed; a one-line contrast in your answer earns the mark cleanly.
• In Simpson's Index questions, show your working, carry full decimals through, and state the value with the point that a higher $D$ means greater diversity.
• Use precise terms: endangered, extinct, invasive alien species, genetic diversity and reintroduction are all credited over everyday wording.