Over the past few hundred years, as human populations have grown and technology developed, our impact on wildlife around the world has increased dramatically. But while we have killed off many plants and animals, recently we’ve been able to protect some and even brought others back from the brink of disappearing forever.
For a species to survive there needs to be a viable population with enough healthy individuals able to reproduce. Large mammals such as elephants are particularly vulnerable to extinction because they take a long time to reach sexual maturity.
The St Helena ebony is critically endangered due to its low genetic diversity. Introduced goats ate all but 2 plants before they were removed from the island to protect these rare individuals. © Claire Woods, CC BY-NC-ND 2.0
Genetic diversity is very important for species' survival as it makes them more resilient to change. Diverse populations are likely to be less vulnerable to disease and the impacts of climate change than genetically uniform populations such as highly inbred crops.
There are 2 ways to carry out conservation:
Many conservationists prefer the in situ approach as it means species can evolve and adapt with their habitat, increasing their chances of survival. However, ex situ is an important alternative, particularly if the population is at a critical size or damage to the habitat is too great.
This was the case for 2 pupfish species from Mexico, Cyprinodon alvarezi and C. longidorsalis, whose natural habitat was drained of water for agricultural use. Now without a home, these fish are being looked after by a number of zoos, including ZSL London Zoo, where they are part of a captive breeding programme. They will be reintroduced if their habitat is ever restored.
The kakapo is critically endangered. Conservationists are managing the remaining population on remote islands to try to save the species. © Mnolf, CC BY-SA 3.0
New Zealand's kakapo, Strigops habroptila, is the only flightless parrot left on Earth. It once roamed the mainland but by 1995 there were only 50 known surviving birds. Numbers are slowly rising thanks to a recovery programme where the birds have been moved to 3 offshore islands that have been freed of the introduced cat, rat and stoat predators.
The Millennium Seed Bank Partnership coordinated by the Royal Botanic Gardens, Kew, is the largest ex situ plant conservation project in the world. It aims to conserve the seeds of 25% of the world’s wild plant species by 2020, with a focus on endangered plants and those that are most likely to be of use in the future.
Seeds stored in the vast vault in Sussex will survive for decades, available to help restore habitats, for use in medicines and to improve crops. Seeds from 10% of wild plant species have already been successfully banked, including those from 6 species that are now extinct in the wild.
Advances in DNA research techniques are offering new ammunition in the fight to conserve species at risk of extinction.
DNA barcoding enables scientists to use specific small regions of DNA to identify species, making identification from tiny amounts of tissue possible. This is extremely useful in helping to combat the illegal trade of products made from protected species.
Barbary lion, photographed in Algeria in about 1893 by Sir Alfred Edward Pease
Museum specimens are playing a crucial role in the conservation of species that are now extinct in the wild or that are no longer found in their original habitats.
By analysing their DNA, scientists can find out which surviving animals are most similar genetically to the original population that died out. This can then inform selective breeding and reintroduction strategies. Researchers are using this approach to try to save the Floreana mockingbird and Barbary lion, for example.
Scientific advances mean that it is technically possible to clone a species back into existence with a well-preserved and complete sample of an animal’s DNA and a compatible host mother.
Shortly before the death of the last known Pyrenean ibex, Capra pyrenaica pyrenaica, a sample of its skin was collected. In 2009, researchers successfully cloned the ibex by transplanting DNA from the preserved tissue into egg cells from a domestic goat. However, although one clone survived pregnancy, it died shortly after birth due to lung defects.
The near-perfect DNA needed to carry out such cloning is simply not available for most species that are already extinct (and certainly not for dinosaurs). But the experiment raises hopes that it may be possible to save endangered species from disappearing completely, even if conservation attempts fail.