A jeep reverses erratically down a muddy track surrounded by a thick palm-tree-fringed jungle. The ground shudders as a huge, leather-skinned tyrannosaurus rex runs in pursuit, its jaws hanging wide revealing a row of razor-sharp teeth as it roars and snaps at the back of the vehicle.

It's a scene many are familiar with from the 1993 adventure film Jurassic Park - and one that many flick back to in their minds when they think about the concept of de-extinction, the science of bringing species, which have disappeared, back to life using genetic technology.

De-extinction is just one way in which man has tried - and continues to try - to stabilize and re-establish lost biodiversity, with other methods including the reintroduction of species that have long-since disappeared from particular regions, or reforestation, growing back sections of forest that have been destroyed.

Despite the research being conducted into de-extinction technology, Jurassic Park is unlikely to be recreated in real life, as the genetic material for dinosaurs is not available, says Michael Hofreiter, a scientist specializing in evolutionary genetics at the University of Potsdam in Germany.

“With dinosaurs it’s not going to happen, their DNA is not preserved in fossil records,” he says. “I’m not sure if we will ever see a de-extinct animal [brought back]. If we do, it’s a long-way off.”

De-extinction – degrees of success

Still, research is being carried out to bring back species that have disappeared more recently, and scientists have had some degree of success. Researchers at the University of Newcastle in Australia were able to bring back the gastric-brooding frog using frozen tissue. Thought to have gone extinct in 1983, when the last known specimen died in captivity, scientists were able to create an embryo of the species although it did not make it further. Scientists have been trying to bring back the frog as part of the Lazarus Project, a scheme run by scientists at the university to develop de-extinction technology to resurrect extinct species.

Meanwhile, other researchers have been trying to bring back the woolly mammoth using DNA from Asian elephants and modifying it to be more like that of the extinct creature for example by adapting genes to give the creature more hair and make it able to store more fat.

But, scientists say it will still not be the same as the mammoths that roamed the earth thousands of years ago.

“It will never be 100% a woolly mammoth,” says Hofreiter. “With the frog...cell transfer is much easier than with the mammoth as there is long-living viable tissue. But if it looks like and functions like the extinct species that would work. It would be tremendously interesting to see.”

Still, the development of de-extinction technology has been the subject of criticism from some who say the investment would be better spent on conservation of existing species and their habitats.

“It pays off much more than putting money into bringing back species that have already gone extinct,” said Volker Homes, director of species conservation for World Wildlife Fund (WWF) Germany. “Take the idea of bringing back the woolly mammoth - since the habitat has changed dramatically, where should we place them and what impact are they likely to have on other species?”

Reintroducing lost species

In contrast to de-extinction, conservation organizations such as WWF work to preserve nature – protecting habitats and biodiversity in countries all over the world. One of the methods used by conservationists is the reintroduction of species into the wild.

“It’s a last resort for species that have become extinct or where numbers are low,” says Homes. “The African white rhino was one of the early species where support by conservation breeding programs dramatically helped the species.”

While many had thought the species to be extinct, a small number of individuals were found in a South African park in the late 19th century. Conservation organizations then worked to save the individuals and reintroduce more into the wild, says Homes.

A similar effort has been made with the European bison, with some 30 individuals being reintroduced in southern Romania following a 200-year absence - a move that the WWF believes will strengthen European ecosystems where the animal plays an important role “through grazing and as prey for larger carnivores, such as bears”, according to a press release announcing the reintroduction.

“Costly but necessary”

Such conservation programs sometimes involve the breeding of threatened or endangered species in captivity before they are then reintroduced in a particular region. Another method is translocation, where a population of a particular species is split with one group remaining where it is and the other being moved to a region where the animal once was, but is now extinct.

WWF is currently working to translocate lions in India. The region in which they are currently located is not able to sustain the 300 individuals and therefore the organization wants to move them, according to Homes.

“In the starting phase we have to work with the people and do capacity building and work with the prey species like deer or cattle,” he says. “But it only happens when we know it is possible to work against the reason the animal became extinct in the first place, for example, because of poaching. A lot of things are done where we are not entirely sure if it works out in the program.”

Homes says such projects are “costly but necessary” to boost and protect populations in the wild.

Like de-extinction, reintroduction is controversial with some critics questioning bringing animals back to an area where they have already died out and the impact that it could have on current species and human communities.

Still, Homes says it is a risk that needs to be taken to ensure the future of, not only the animals being protected, but also the humans who depend on such creatures.

“Humans have to decide whether or not it is valuable to have animals on the land and with free range in nature,” he says. “We depend on everything surrounding us to be intact for our medicine, for food, for timber and wood and the species are a backbone of that. We need to ensure species survive.”