UN: We have 10 years to save Earth's biodiversity 0:46
(CNN) —
When Kurt Benirschke began collecting skin samples from rare and endangered animals in 1972, he didn't have a firm plan for what to do with them.
As a researcher at the University of California, San Diego, he believed that one day the tools would be developed to be used to save these animals.
A few years later, he moved his collection to the San Diego Zoo and named it the Frozen Zoo.
"There was a famous sign hanging above the frozen zoo with a quote that said, 'You must collect things for reasons you don't yet understand,'" says Oliver Ryder, a geneticist at the San Diego Zoo and one of Benirschke's early collaborators.
"We felt like we were stewards of this growing collection that was going to have value for the future in ways we couldn't appreciate at the time."
Benirschke passed away in 2018, but his efforts are very much alive.
Today, the frozen zoo is the largest animal cryobank in the world, with samples of more than 10,500 individual animals from 1,220 species.
For a long time, it was the only project of its kind;
in recent years, however, similar conservation efforts have sprung up around the world, and tools that Benirschke did not yet have are now available.
At the same time, time is ticking for many endangered species.
Oliver Ryder is director of conservation genetics at the San Diego Zoo Wildlife Alliance and geneticist at Frozen Zoo.
'An irreplaceable repository of very rare animals'
Since 1970, populations of mammals, birds, amphibians, reptiles and fish have declined by 68% on average, according to WWF's Living Planet Report 2020.
The report also states that as a result of habitat loss due to human activities, one million species — animals and plants — are threatened with extinction in the coming decades and centuries.
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At the current rate of biodiversity loss, some scientists believe that preserving samples of species that may not be here tomorrow is no longer a visionary endeavor, but rather a scientific obligation.
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"As the effort increased, we realized we were collecting an irreplaceable repository of very rare animals," says Ryder.
"Because we have cells at the Frozen Zoo, we can now apply new techniques and new technologies to broaden our understanding and learn more information that is of direct relevance to preventing the extinction of endangered species."
Since Frozen Zoo was founded, Ryder says, many milestones have been reached in the field of genetics, beginning with the cloning of the first animal, a sheep named Dolly, in 1996. As of 2001, four endangered species have been cloned. from extinction using genetic material from the frozen zoo: the Indian gaur, a wild Asian humped ox;
the banteng, a kind of cattle from Southeast Asia;
Przewalski's horse, once found throughout Mongolia and extinct in the wild until recently;
and the black-footed ferret, which was thought to be extinct in the wild until it resurfaced in 1981, but was then nearly wiped out in an epidemic.
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The Frozen Zoo at the San Diego Zoo Conservation Research Institute contains specimens of more than 1,200 species and subspecies, and is the largest repository of its kind.
So far, four endangered species have been cloned using genetic material stored there.
They include the Przewalski horse, which is native to central Asia.
In 2020, a baby horse known as "Kurt" was born in Texas, cloned with cells from the frozen zoo, the first successful cloning of the species. (Alexei DruzhininTASS via Getty Images)
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In 2001, an Indian gaur, a humped Asian wild ox, was born, sealed with frozen zoo genetic material and gestated in a domestic cow.
Unfortunately, he contracted dysentery and died two days after birth.
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In 2003, the banteng, a species of wild cattle found in Southeast Asia, became the second endangered species to be cloned.
The procedure used cells from the Frozen Zoo, and the male, named Jahava, survived for seven years at the San Diego Zoo.
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The black-footed ferret was thought to be extinct in the wild until a small population was rediscovered in Wyoming in 1981, but was decimated by disease.
A clone named Elizabeth Anne was born in 2020 thanks to genetic material from a ferret that had been stored at the frozen zoo since 1988, the first time a native endangered species had been cloned in the US. It is hoped the cloning could help restore genetic variation in the surviving population.
(Kathryn Scott Osler/The Denver Post via Getty Images)
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The Saudi gazelle once roamed the Arabian Peninsula, but this century it was declared extinct.
The Frozen Zoo has a bank of its cells dating back to the 1990s. (KARIM SAHIB/AFP via Getty Images)
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There are only two northern white rhinos left in the world, both female.
The Frozen Zoo has cell cultures from 12 northern rhinos and has used frozen skin cells to grow stem cells, which could be used to create sperm and eggs.
(TONY KARUMBA/AFP via Getty Images)
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The hope is that northern white rhino embryos can gestate into the closely related southern white rhino.
The Zoo's Reproductive Sciences team is using southern white rhinos to develop techniques including artificial insemination, in vitro fertilization and embryo transfer.
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genetic rescue
Although cloning is not perfect—the cloned Indian gaur only survived 48 hours—it is a useful tool to help save endangered species, as it can increase genetic diversity.
When the population of a species declines, the remaining animals are forced to reproduce and the gene pool shrinks, further threatening survival.
But the cloned black-footed ferrets, for example, were born in 2020 from samples collected in 1988, which meant that their genetic profile was much more varied than that of today's population.
"In a species of animals, genetic diversity is what gives it its resilience, its ability to bounce back from natural disasters, virus attacks, disease attacks. That's because if there are more different types of genetics in a species, there's a chance that some will survive," says Brendon Noble, a professor of regenerative medicine at the University of Westminster in London and chairman of the board of directors of The Frozen Ark, a UK-based animal cryobank.
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Frozen Ark (Frozen Ark, in Spanish) was founded in 2004, with a similar intention to that of the Frozen Zoo but with a different structure: instead of a single collection linked to an institution, it is a distributed network of more than two dozen institutions, such as zoos, museums, and universities spread across the globe, each sharing their own collection and knowledge.
While the Frozen Ark has more samples than the Frozen Zoo (48,000 out of 5,500 species), about 90% of them are made up of DNA rather than living cells, which are used differently and must be stored at much lower temperatures.
DNA samples cannot be used to clone an animal, but they are essential to capturing the genetic blueprint of species that could become extinct.
"That information can be used for a wide range of different scientific studies, from cancer research to understanding recovery processes such as limb regrowth," says Lisa Yon, associate professor of zoo and life medicine. wildlife at the University of Nottingham and scientific adviser on Frozen Ark.
"By saving these resources we will enable not only current scientists, but also future generations of scientists to make all kinds of new discoveries."
At the frozen San Diego Zoo, the specimens are kept in cryogenic tanks.
"The collection is duplicated; periodically we take samples and move them to another facility, so that all the cells are not in one place," says Oliver Ryder.
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Cell freezing involves a more delicate process than with DNA, to prevent the formation of ice crystals when cells are frozen at -320 degrees Fahrenheit (-196 Celsius).
Different cells also require different freezing procedures;
for example, amphibian cells are difficult to freeze properly and are therefore severely underrepresented in cryobanks.
And some of the technologies that would make the best use of cell lines still need to be perfected.
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"A lot of the things we want to do we can't do yet," says Tullis Matson of Nature's Safe, a UK-based cryobank that collects live cells and gametes (sperm and egg cells).
He predicts that in the next 10 to 30 years it will be possible to turn these cells into pluripotent stem cells, which can be reprogrammed to produce sperm and eggs.
Once that is possible, an embryo could be created from the sperm and egg, and then implanted into a surrogate individual of an endangered species, once again providing much-needed genetic diversity.
Tullis Matson founded Nature's Safe in November 2020. "It's a safety net," he says.
The challenges ahead
The accelerating climate crisis will put further pressure on ecosystems, making the work of cryobanks even more important.
“I see cryopreservation as the absolute cornerstone of conservation. We are facing the sixth mass extinction right now, and we need to be able to provide future generations with a way to bring these species back to life,” says Matson.
Many of the problems facing these projects are of a practical nature.
"Safeguarding the Frozen Zoo in the future is one of the biggest challenges," says Frozen Zoo Curator Marlys Houck.
"We want to continue to collect more samples while making sure the ones we already have will be there beyond our lifetimes. This includes making sure there is dedicated funding for liquid nitrogen [to freeze DNA] and replacing cryotanks as we go." grow old."
Marlys Houck, curator of the Frozen Zoo, has been working to save the northern white rhino from extinction and plans to use southern white rhinos as stand-ins for northern white rhino embryos.
"There are many challenges ahead, but the researchers are optimistic that a northern white rhino calf could be born from these processes within 10 to 20 years," she says.
One of the main challenges will be convincing conservation agencies that cryobanking is a valid strategy and worth funding.
"Many of us are doing this without any tangible support beyond donations or grants, without national or government support," says Yon.
"Cryobanking is increasingly recognized as a vital resource, so it's a bit disconcerting that there isn't more financial support."
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Finally, all researchers agree that closer collaboration between all cryobanks is necessary to be successful.
"The task is huge, no one can do this on their own," says Matson.
"There are a million species at risk. We need 50 different genetic samples of each, which means 50 million samples; for each of them, we need five vials for each sample, so hundreds of millions of samples have to be stored. ".
Ryder says that he is working to develop a global network to store material that has already been collected.
"If we had a conversation with the future, they would say, please save as much biodiversity as you can, now. Period," he adds.
"And they would say, do that by any means available."
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