Late last year, the U.S. Fish and Wildlife Service proposed removing 23 species from the Endangered Species List, but not for the reason you might hope.
All 23 species of birds, fish, and mussels have gone extinct, according to the USFWS, and are no longer eligible for listing under the Endangered Species Act.
Many of these species have been on the decline for decades. Some, like the Hawaiian Kauai nukupuu bird, haven’t been spotted since the 19th century. As the USFWS explained in its press release, ESA protections came “too late” to conserve habitat and protect these animals from invasive species and disease.
Some believe biobanking can save other animal populations from the same fate. Wooly mammoths probably aren’t on that list, but biobanking advocates say animal cells frozen in cold storage could be used to beef up the genetic diversity of captive populations and restore some species from the brink of extinction.
Biobanking refers to the collection and storage of biological materials. There are many kinds of biobanks designed for different purposes, but conservationists are particularly interested in biobanks like San Diego Zoo’s Frozen Zoo.
As its name suggests, the Frozen Zoo stores living animal cells by super-freezing (the technical term) those cells at -196 degrees Celsius. Virtually all cell activity stops at this temperature, which allows scientists to store samples until they want to use them. These cells can come from anywhere on an animal’s body and often include reproductive cells like sperm and eggs.
The Frozen Zoo launched in 1975 and has since been able to store 1,100 species of vertebrate animals and cells from over 10,000 individual animals, according to Dr. Oliver Ryder. Dr. Ryder is the Frozen Zoo’s Director of Conservation Genetics, and he spoke to MeatEater about the importance of banking the cells of endangered animals.
“We’re seeing species decline in numbers, populations disappear from within their range due to habitat loss and fragmentation. For some species, more of their gene pool is in these freezers than is in the wild,” Dr. Ryder told MeatEater.
Most of the Frozen Zoo’s samples come from animals at the San Diego Zoo, where biologists can collect cells during an animal’s regular checkups or postmortem examinations. The Frozen Zoo tries to bank a diverse collection of animals, but time and space constraints force them to select vulnerable species over less vulnerable ones.
The Frozen Zoo isn’t alone. Among other biobanks related to animal conservation, the Rare Breed Survival Trust in the United Kingdom houses a gene bank of native livestock breeds, the National Oceanic and Atmospheric Administration houses the National Marine Mammal Tissue Bank (NMMTB), and Japan’s National BioResource Project houses animal and plant materials to advance scientific research.
Freezing biological specimens might sound like something out of Mel Gibson’s 1992 movie, “Forever Young,” but the reality is less science fiction and more science class.
Frozen zoos can help researchers investigate parentage, genetic lineage, evolutionary history, and disease susceptibility of individuals or species. However, a biobank’s greatest conservation potential is its ability to beef up the genetic diversity of captive breeding programs.
Captive breeding programs are expensive, but the biggest hurdle is maintaining healthy genetic diversity. This issue is especially concerning for species that do not exist in the wild. A small captive population will eventually die out without new individuals to introduce genetic diversity.
This almost happened to the black-footed ferret. The black-footed ferret is the only ferret native to North America, but the population was so small by the late 20th century that the species was thought to be extinct.
Conservationists found the last remaining wild population in 1981, but only seven of those 18 ferrets produced kits. The captive breeding program for the black-footed ferret has successfully produced thousands of ferrets, but the entire population descended from those seven individuals.
Fortunately, biologists in the 1980s preserved a tissue sample from one of the non-breeding female ferrets and sent that sample to the San Diego Frozen Zoo. Those cells were preserved until 2020, when a group of scientists created a ferret embryo from that tissue, which was born later that year.
This cloned ferret, dubbed “Elizabeth Ann,” is not related to any black-footed ferret currently in existence and could provide some much-needed genetic variation to the population. She is the first clone of a native endangered species in North America.
“It was like discovering a new ferret,” Dr. Ryder said.
It’s unclear whether Elizabeth Ann is necessary to the black-footed ferret’s continued success. The Smithsonian’s National Zoo & Conservation Biology Institute has released thousands of black-footed ferrets in partnership with the USFWS, and they don’t report a lack of genetic diversity as one of the population’s primary threats.
But in a press release announcing Elizabeth Ann’s birth, the USFWS pointed out that the ferrets must overcome “unique genetic challenges” and could eventually become more susceptible to disease, infertility, and “genetic abnormalities.”
In any case, if Elizabeth Ann proves to be fertile (researchers will know later this year), the project will provide powerful proof of concept for how biobanking can save threatened species.
Researchers at the Australian Frozen Zoo are also offering a less dramatic way biobanking could theoretically introduce genetic diversity into captive breeding populations. Biobanked sperm, researchers argue, can allow captive programs to operate with fewer animals while maintaining the diversity needed for a healthy population.
“Using frozen zoos could provide a 25-fold increase in the number of species that could be conserved. This would be a staggering conservation achievement, and we think it can be done,” said Dr. Simon Clulow of Macquarie University in Sydney.
Clulow and his colleagues published a paper in 2020 arguing that introducing biobanked frozen sperm to an Oregon spotted frog breeding program could significantly reduce the cost of the program. They suggest that backcrossing—crossing a hybrid with one of its parents or a creature genetically similar to its parent—with frozen sperm every generation would lead to much lower costs than with traditional captive breeding.
Reducing the cost of captive breeding programs will free up resources to conserve species other than the so-called “charismatic megafauna” that generate the most funding and attention.
Not all conservationists are quite as excited about using biobanked material in these ways. Dr. Stuart Pimm is the Doris Duke Professor of Conservation Ecology at Duke University, and he worries that “de-extinction” techniques (which are still largely theoretical) can give moral cover to people and organizations that want to destroy habitat.
“If you think it’s OK to drive species to extinction because you think we can keep their DNA going, it creates an awful moral hazard,” Dr. Pimm told MeatEater.
Resurrecting ancient species like the wooly mammoth gets a lot of play in the news (not to mention Hollywood), but when asked about mammoths, Dr. Ryder sounded skeptical. Both he and Dr. Pimm argued that mammoth resurrection isn’t practical. Dr. Ryder noted that no viable mammoth DNA exists with which to make a clone, and Dr. Pimm wondered how scientists would reconstruct mammoth habitat and ecosystems.
But while Dr. Ryder is still interested in using genetic technology to save declining species, Dr. Pimm has personal experience that keeps him wary of anything that rhymes with “de-extinction.” When he testified before Congress in the mid-1990’s about the reauthorization of the Endangered Species Act, members of Congress expressed unconcern with habitat destruction because endangered species could be resurrected a la Jurassic Park.
“There are people who would like to push environmental destruction to the limit, so the moral hazard of de-extinction is a real danger,” Pimm said.
Instead of using time and resources to pursue the kind of genetic strategies made possible by biobanks, Dr. Pimm would like to see conservationists focus on what works: habitat restoration, legislative protections, and public education.
“The amount of time people are wasting on these de-extinctions, they could get off their arses and do something useful for conservation,” he said. “I think they’re doing a considerable amount of harm in giving people false solutions. That’s not how we’re going to save biodiversity.”
When asked about Dr. Pimm’s “moral hazard,” Dr. Ryder agreed that it’s a “legitimate concern” and acknowledged that solutions like Elizabeth Ann are still highly experimental. We can’t bank all our conservation efforts on their success, he said.
He took issue, however, with the contention that the two approaches represent a zero-sum game.
“That argument would presume that focusing effort on banking cells would detract from efforts to save species. All the evidence is to the contrary. The effort to save species is as strong as ever and is supported by international treaties and national legislation and regulation,” he pointed out.
For his part, Dr. Pimm was careful to distinguish between “de-extinction” technologies and biobanking more generally. He does not support the former, but the latter he described as “essential” to conservation efforts. Storing genetic material is not a problem; what matters is how we use it.
Both scientists agreed that conserving threatened and endangered species requires a collaborative, multi-pronged approach. Dr. Ryder stressed that habitat conservation should always be a top priority, and Dr. Pimm said he could support promoting genetic diversity via biobanked material if those techniques proved to be effective.
Ultimately, Dr. Ryder believes conservationists should pursue the kinds of solutions he’s spearheading at the Frozen Zoo in the hopes that they won’t have to use them.
“My hope is that we won’t need to do these kinds of things because we won’t have species that are so depleted in their genetic variation or on the brink of extinction that we have to evoke these heroics,” he said.
“But given that we’re seeing a number of species in decline, it would be prudent, thoughtful, and helpful to bank cells now so that we have that option in the future,” he continued. “I would like to see a greatly expanded effort to do banking so that we wouldn’t need to be looking at a future where we’re inevitably seeing the genetic diversity of wild species erode.”