Humans have proven adept at wiping out vast numbers of animals. Can we atone by saving species through captivity breeding?

When 200 captive-bred frogs were set free in an ancestral swampland in South Africa recently, their simple homecoming ceremony gave scientists several reasons to cheer loudly.

The tiny Pickersgill’s reed frogs – each the size of an adult thumbnail – were making history of a kind, by hopping one step further away from the abyss of extinction.

It was a small dose of encouraging news at a dismal time for conservationists. Study after study shows how human encroachment is annihilating wildlife and insect populations. The latest WWF estimate this week found that people have wiped out 60 percent of animal populations since 1970.

The question is: can we become as good at saving species as we are at destroying them?

In the case of the frogs, rapid expansion of farming and other development near the South African port city of Durban has reduced their remaining kingdom to a land area of only 144 sq km (56 sq miles).

But thanks to captive breeding, the 20-strong population has multiplied tenfold in only one year in a project run by frog experts Dr Adrian Armstrong and Dr Jeanne Tarrant.

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They are not sure how many will reach old age in the wild, but the turbo-boosted population growth gives them hope that this threatened species has a better shot at survival, in combination with other conservation action.

The Durban frogs are not alone in being on the brink of survival, and their rescue begs a question: can species be rescued by programmes like this in which they are bred in captivity?

Worldwide, more than 26,000 wild species face extinction and are listed as such on The IUCN Red List of Threatened Species.

Dr Richard Young, head of conservation science at the UK-based Durrell Wildlife Conservation Trust, says the true number facing extinction is likely to be much, much higher, as scientists have yet to formally classify or assess the multiple forms of life on our planet.

Of the more than 93,500 species assessed so far, Young says it looks like 41% of amphibians are threatened with extinction, along with 25% of mammal species, 13% of birds and 33% of corals.

No surprise then that conservation experts are resorting to some pretty desperate measures to protect and multiply vulnerable species before it’s too late.

Breeding them rapidly in captive or semi-captive conditions is one strategy, largely pioneered by Welsh ecologist and Durrell chief scientist Prof Carl Jones, who was awarded the 2016 Indianapolis Prize for his role in saving nine species of wildlife from extinction.

Over the last 35 years, Jones and fellow scientists have been involved in projects to protect more than 50 threatened species, mainly in Mauritius and Madagascar.

Numerous similar restoration projects are underway globally, says Dr Kathy Traylor-Holzer, senior program officer at the Conservation Planning Specialist Group of the International Union for the Conservation of Nature (IUCN).

She says examples include the Iberian lynx in Spain, the Eastern sarus crane in Thailand, the Kihansi spray toad in Tanzania, golden lion tamarins in Brazil or American burying beetles in the US.

And while the conservation benefits of captive breeding and other techniques to artificially boost the number of threatened species may seem obvious, there are still some question marks about just how far scientists should go in managing or manipulating the living conditions of species they are trying to save.

Young and his Durrell colleague Dr Andrew Terry acknowledge that intensive breeding is “something of a last resort”.

“These programmes are expensive, complicated and difficult,” says Terry. “If you are breeding species with the intention of putting them back in the wild, you have to monitor the outcomes very carefully and also ensure that you don’t introduce new diseases or pathogens back into the wild by accident.”

Facebook Twitter Pinterest A pygmy hog at a conservation project in Assam, India, where the animals receive supplementary feed in a rewilding environment. Photograph: CMJ/Durrell Wildlife Conservation Trust

Because they are dealing with species that often have very low genetic diversity, project managers must also guard against the potential for inbreeding.

“You can’t always breed animals in captive conditions and simply open the cage doors. Sometimes they need a bit of time to adapt to predators and learn what to eat in their new environment.”

He cites the example of the Pygmy Hog Conservation Project in Assam, India, where captive-bred hogs are released into a large enclosure containing plants found in their wild environment.

“They still receive supplementary feed in the enclosure but we try to eliminate all human contact so that the young animals start to learn to support themselves. Then we move them to soft release areas to acclimatise, and to leave at their own speed. After three to four weeks, we find them coming back less often for supplementary food.”

Young says the survival rate for captive-bred animals varies greatly, depending on the species: “With amphibians you expect a high mortality rate, but when we released ploughshare tortoises back to the wild, we experienced a near 100% survival rate.”

Facebook Twitter Pinterest Survival of the slowest Photograph: Tim Flach/Durrell Wildlife Conservation Trust

Is there a point that should not be crossed with intensive management and other emerging de-extinction projects?

“Yes, in my view, there probably is a line,” says Young. “We need to focus more on the species that are still with us, rather than those that are already extinct. There are possibly 70-80 Sumatran rhinos left alive, so it does not feel right to be investing in trying to bring the woolly mammoth back to life, instead of saving the Sumatran rhino.”

Following the recent death of Sudan, the last Northern white rhino male, Edinburgh Napier University ecologist Dr Jason Gilchrist panned expensive plans to resuscitate extinct or near-extinct species.

In an article published in The Conversation, Gilchrist argued that instead of investing in “Jurassic Park” technology, such money was better spent on protecting the Southern white Rhino, Asian rhinos and other threatened species.

“You can’t just pluck a species off the extinct-shelf, like the woolly mammoth, and put it back in an ecological niche that no longer exists. But, we are facing an absolute crisis,” says Terry. “So there is also a place for new cutting-edge technology. Some might seem outlandish today, but in a few decades they will become commonplace.”

“What we find so frustrating is that global biodiversity loss is happening under the radar, whereas there should be international outrage before it slips away,” says Terry.

“It should be right at the top of the global political agenda.”

This article is part of a series on possible solutions to some of the world’s most stubborn problems. What else should we cover? Email us at theupside@theguardian.com