What maintaining biodiversity means

1. Maintaining biodiversity means keeping the range of different species in an area, not simply keeping the total number of organisms high.
2. Local biodiversity is the variety of species in one habitat, such as a pond, a hedgerow or a stretch of moorland.
3. Global biodiversity is the variety of species across the whole planet, and a species lost globally can never be replaced.
4. A species can disappear locally while still surviving elsewhere, so local losses are often reversible by restoring the habitat and bringing the species back.
5. Conservation decisions weigh the benefits of keeping biodiversity against the cost of the scheme and against what the land, water or animals would otherwise be used for.

Benefits for the ecosystem

1. Species in a community depend on one another for food, shelter, pollination and the recycling of nutrients, so the community only works while all of those roles are filled.
2. A community with high biodiversity is more stable, because a predator that loses one prey species can switch to another and the disturbance is absorbed.
3. A community with few species has few alternatives, so the loss of one species can cause several others to disappear with it.
4. Insect pollinators such as bees and hoverflies are needed for the reproduction of most flowering plants, so their loss would remove the plants that many other species feed on.
5. Decomposers break down dead material and release mineral ions back into the soil, and without them nutrients would stay locked in dead bodies rather than returning to plants.
6. Plant roots bind soil particles together, which slows erosion, while woodland and peat soak up rainfall and reduce flooding downstream.
7. Photosynthesis by forests, grassland and marine algae removes carbon dioxide from the atmosphere and releases oxygen, so vegetation regulates the composition of the air.
8. Predators and parasites keep the numbers of potential pests down, which reduces how much pesticide a farmer has to use.

Benefits for people

1. Every crop and farm animal was bred from a wild species, so wild populations are the original source of the food supply.
2. Wild relatives of crops still carry alleles for disease resistance, drought tolerance and higher yield that modern varieties have lost, and plant breeders cross those alleles back in.
3. A species that becomes extinct takes those alleles with it, so the raw material for future crop breeding shrinks every time one is lost.
4. Many medicines were first isolated from wild organisms, including aspirin from willow bark, digitalis from the foxglove and penicillin from a mould.
5. Only a small fraction of species has ever been tested for useful compounds, so an unstudied species may hold a future drug that is lost if it becomes extinct.
6. Wild species also supply raw materials such as timber, fibres, dyes and rubber.
7. Fishing, forestry, farming and tourism all depend on healthy ecosystems, so biodiversity supports jobs and income directly.
8. People also value wild places for walking, watching wildlife and study, which is harder to price but is one reason nature reserves attract public funding.

Small populations are hard to rescue

1. A population that has fallen to a few dozen individuals carries only the alleles those individuals happen to have, so its gene pool is small.
2. Every mating in such a population is between close relatives, which is inbreeding.
3. Close relatives carry the same alleles, so their offspring are far more likely to inherit two copies of a harmful recessive allele and show the condition it causes.
4. Inbred populations therefore tend to have lower fertility, more offspring that die young and more inherited disorders, which pushes the numbers down further.
5. Low genetic variation also removes the raw material for natural selection, because selection can only act on differences that already exist.
6. If a new disease arrives, few individuals are likely to carry an allele for resistance, so a single outbreak can remove the whole population.
7. The same is true of a change in conditions such as a hotter, drier summer, so a species with little variation is less able to adapt over generations.
8. Conservation therefore aims to keep populations large and connected, because a large connected population holds more alleles than several small isolated ones of the same total size.

Challenges of conservation schemes

1. Conservation costs money, and wardens, fencing, vehicles, veterinary care and survey work all have to be paid for every year rather than once.
2. Protected land cannot be used for housing, farming, logging or mining, so protecting a habitat always means giving up the income that use would have produced.
3. Local people may depend on that land for food, fuel or work, so a scheme that ignores them takes away a livelihood and is resisted.
4. Schemes therefore work best when local communities are employed by them and gain an income from the protected habitat, so that protecting it is worth more to them than clearing it.
5. Poaching continues wherever the price paid for ivory, horn or skins is high and the chance of being caught is low.
6. Reserves are often huge and remote, so patrolling every boundary is expensive and in practice incomplete.
7. Populations recover over decades while funding is usually granted for a few years, so a scheme can be stopped before anyone can tell whether it worked.
8. Protecting one species can also conflict with protecting another, for example when a growing population of a protected grazing animal strips the vegetation that other species depend on.

Reaching international agreement

1. Migrating animals, river pollution and changes in the atmosphere all cross national borders, so a country acting alone cannot protect the species that move through it.
2. Trade in endangered species is international as well, so a hunting ban in one country achieves little while the market in another country still pays for the product.
3. Countries hold different priorities, and a nation trying to lift its population out of poverty may see a restriction on logging or fishing as blocking development that wealthier nations already had.
4. International agreements are usually voluntary, so there is no court that can force a government to keep to a target it has signed.
5. Negotiations take years because every country has to agree, and a government that changes can withdraw from what the previous one signed.
6. Agreements are more likely to hold when wealthier countries pay towards the cost, share technology and fund the monitoring, so the burden does not fall on the poorest nations alone.

Monitoring whether a scheme works

1. A count taken before the scheme starts, called the baseline, is essential, because without it there is nothing for later counts to be compared against.
2. The same sampling method is then repeated at the same sites and at the same time of year, so that a change in the figures reflects the population and not a change in technique.
3. Plant and slow-moving species are counted by sampling, mobile animals are estimated by marking and recapturing, and both give an estimate with a margin of uncertainty rather than an exact figure.
4. Satellite images measure how much forest cover remains, and camera traps, leg rings and radio tags record which individuals are still alive and where they travel.
5. Monitoring is difficult when a species is rare, nocturnal, shy or spread thinly over a vast area, which is exactly the situation for most endangered species.
6. Numbers also change for reasons unconnected with the scheme, such as a hard winter or an outbreak of disease, so several years of data are needed before a trend can be claimed.
7. Genetic testing of samples adds a second measure, showing whether the number of different alleles in the population is being maintained as well as the number of individuals.

Ecotourism

1. Ecotourism is managed so that the habitat survives the visit, using small groups, local guides, marked paths and hides, temporary accommodation and waste carried away from the site.
2. The entrance fees and permits pay directly for wardens, fencing, vehicles and research, so the habitat funds its own protection.
3. Local people are employed as guides, drivers and staff, which gives a community a reliable income that depends on the wildlife staying alive.
4. A living animal watched by paying visitors year after year is then worth more than the single payment a poacher would receive, which changes the incentive.
5. Visitors who have seen a species close up are also more likely to support conservation once they are home.
6. Ecotourism still has costs, because flights and vehicles release carbon dioxide and the journey may do more damage than the visit prevents.
7. Too many visitors trample vegetation, erode paths, leave litter and disturb animals that are feeding or breeding, so numbers have to be capped and sensitive areas closed in the breeding season.
8. The money can also leave the area entirely if the tours are run by companies based elsewhere, in which case local people gain nothing and the incentive disappears.