Bring extinct species back to life?

A Saola is caught on camera for the first time in 15 years on September 7 in a forest in Vietnam. The species was discovered in 1992, and at most a few hundred -- and as few as a couple dozen -- of the animals are thought to exist. Because of its rarity and elusiveness, the saola is dubbed the "Asian unicorn." They are recognized by two parallel horns with sharp ends, which can reach 20 inches in length and are found on both males and females.

A Javan rhino walks in the national park in the Ujung Kulon National Park in Indonesia. It is one of the most threatened of the five rhino species, with as few as 35 individuals surviving. Their skin has a number of loose folds, giving the appearance of armor plating. The discovery of three dead Javan rhinos in 2010 has intensified efforts to save one of the world's most endangered mammals from extinction.

The Ganges River dolphin once lived in the Ganges, Brahmaputra, Meghna, Karnaphuli and Sangu rivers of Nepal, India and Bangladesh. But the species is extinct from most of its early distribution ranges. They can only live in freshwater and essentially are blind. They hunt by emitting ultrasonic sounds, which bounce off of fish and other prey, enabling them to "see" an image in their mind.

A strutting adult male greater sage-grouse is seen in Alberta, Canada. They were once found across 13 western U.S. states and three Canadian provinces. Because of oil and gas development, conversion of land for agricultural use, climate change and human development, they now only inhibit half their historic range. They are well known for their spectacular mating dances performed on mating grounds called "leks."

A schoolboy reaches out to touch a humpheaded Maori wrasse as it swims in the world's largest Great Barrier Reef exhibit at the Sydney Aquarium in June 2003. It is an enormous coral reed fish—growing over 6 feet long — with a prominent bulge on its forehead. Some of them live to be over 30 years old. WWF urges local governments in the Coral Triangle to stop the trade and consumption of humphead wrasse, one of the most expensive live reef fishes in the world.

A baby Buergers tree kangaroo appears out of her mother's pouch at the San Diego Zoo in January 2003 in San Diego, California. The endangered species of tree kangaroo is native to the lowland and mountainous rainforests in Papua New Guinea and Indonesia. They have adapted to life in the trees, with shorter legs and stronger forelimbs for climbing, giving them the appearance of a cross between a kangaroo and a lemur. The joey plays a critical role in the Tree Kangaroo Species Survival Plan, a breeding program that has worked to ensure the long-term survivability of the species since 1977.

Black spider-monkeys — also known as the Guiana or red-faced spider monkey — are one of the main monkey species encountered in healthy tropical rainforests. It's prehensile tail allows this monkey to find stability when sitting on branches and to reach out for food at the tip of fragile branches by suspending himself.

A leatherback turtle goes to sea after burying eggs at the Matapica National Park. They are named for their shell, which is leather-like rather than hard. They are the largest sea turtle species and also one of the most migratory, crossing both the Atlantic and Pacific oceans. Although their distribution is wide, the number of these turtles has seriously declined during the past century as a result of intense egg collection and fisheries bycatch.

The rockhopper penguin is much smaller in size than the emperor penguin. Rockhopper penguins weigh less than 10 pounds. They were named for their distinctive hopping movements over the rocky hills and cliffs where they live and breed. In the past 30 years, it is estimated that the population of rockhoppers has fallen by nearly 25%, and now climate change could place them at even greater risk.

A bowhead whale swims under ice in the Arctic. Adult bowheads are entirely black except for the front part of the lower jaw, which is white and prominently upturned. They can grow up to 60 feet long while still being able to leap entirely out of water. Data show they may be among the longest-living animals on Earth. Based on the recovery of stone harpoon tips in their blubber, and from analysis of eye tissue, scientists believe that the life-span of bowhead whales can be more than 100 years.

The pronghorn antelope is the fastest hoofed animal in North America and is capable of reaching speeds up to 60 mph. Most pronghorn populations remain stable, but have experienced a historic decline. Pronghorn follow the same migration corridors year after year. Today, the thoroughfares that link the summer breeding grounds and winter grazing areas are being fragmented by roads, cities, fences and energy development. These fragmentations threaten the migratory routes and survival of pronghorn.

• Scientists are working to revive extinct species with advances in genetics


• The field has been termed 'de-extinction' science


• John Sutter: The research is promising


• But Sutter argues it shouldn't distract from essential efforts to protect biodiversity

Editor's note: John D. Sutter is a columnist for CNN Opinion and creator of CNN's Change the List project. Follow him on Twitter, Facebook or Google+. E-mail him at ctl@cnn.com. The opinions expressed in this commentary are solely those of the author.

(CNN) -- I almost thought the question was a joke.

Submitted by a reader in response to my recent story on the illegal pangolin trade, it went something like this: Should we be as concerned now as we once were about a rare species disappearing, given that we might be able to use future technology to "Jurassic-Park" an extinct creature back into existence?

Of course not, right? That's such a sci-fi concept. One for Hollywood, not for actual scientific and ethical consideration.

As I learned more about the science of "de-extinction," however, I started to realize how serious that question actually is.

It's not whether we will be able to revive extinct species.

That seems likely, in some form or another.

The debate needs to focus on other areas: "Should we?" and "Where will they live?" And does that change our approach to conservation?

First, a brief introduction to what we know about de-extinction.

In 2003, scientists revived the bucardo, a Spanish mountain goat, from DNA that was frozen before the species went extinct. They implanted a goat egg with bucardo genes and then used a goat-ibex mix as the surrogate parent. The animal that contained once-extinct DNA survived only a matter of minutes, but it was heralded as the first de-extinction on Earth, and researchers are trying again.

Other efforts are underway to revive the passenger pigeon, which was hunted to extinction a century ago, from DNA collected from museum specimens.

I called up George Church, a professor of genetics at Harvard Medical School, and one of the most prominent de-extinction backers, to ask how real this technology is.

"It's already happening," he told me.

The example he gave wasn't a bird or goat.

It was the woolly mammoth.

No one will be able to re-engineer a woolly mammoth that is genetically identical to those that roamed Siberia 10,000 years ago, he said, but we will be able to make something close, likely using elephants as a surrogate. Scientists already have "brought back several mutations (from woolly mammoth DNA) and put them into elephant cells successfully," he said.

Church and others, like Stewart Brand, find these prospects incredibly exciting.

"The fact is humans have made a huge hole in nature in the last 10,000 years. We have the ability now and maybe the moral obligation to repair some of the damage," Brand -- who is founder of the Whole Earth Catalog and is one of our premier thinkers on the environment and technology -- says in a 2013 TED Talk.

"Most of that we'll do by expanding and protecting wild lands -- by expanding and protecting the populations of endangered species. But some species that we killed off totally we could consider bringing back to a world that misses them."

I generally agree with the premise that society should pursue science for the sake of science itself. Look no further than NASA's inventions -- CAT scans, computer microchips, personal water filters -- to understand why that makes some practical sense.

But arguing that de-extinction is to nature what hitting "control+Z" is to changes in a Word document strikes me as potentially negligent.

There are some sins that can't be easily undone.

"In practical terms, in the near future in which action is required, extinction is certainly 'forever,'" writes Paul Ehrlich, a professor at Stanford and founder of the university's Center for Conservation Biology.

There are primarily three reasons for this, as Ehrlich and others have argued:

1. Species need a habitat: Climate change, deforestation and illegal hunting are wrecking entire ecosystems. What's the point in bringing back a pangolin, a weird creature I came to love, if it doesn't have a place to live, or will be hunted again? In a National Geographic podcast, the journalist Carl Zimmer smartly notes that a revived species without a viable habitat could be seen as a "freak show." I asked Church about this and he suggested re-engineering DNA to fit the new ecosystem. Perhaps, but doesn't that sound needlessly complicated compared to protecting what we've got?

2. It's a "moral hazard": As Ehrlich argues in a piece for Yale Environment 360, the prospect of de-extinction science makes protecting the existing environment seem less essential. Again: thinking there's an "undo" button can be dangerous.

3. Have you seen "Jurassic Park?": Any advance in science, especially dealing with ecosystems, has unintended consequences. This is especially apparent in the plot of "Jurassic Park," the 1993 blockbuster in which dinosaurs are brought back from extinction for our amusement -- and end up eating us. Some impacts could be subtler but still significant. Earlier this year, for example, the U.S. Army Corps of Engineers estimated ridding the Great Lakes and Mississippi River basin of invasive Asian carp, which have been known to "dominate" native ecosystems, pushing other species out, could cost billions. Who's to say a de-extinct species wouldn't become a similar nuisance, competing with still-living species?

It's possible to pursue de-extinction science and also not use any future developments as an excuse to shirk on conservation. But we have to remind ourselves that extinction, for now, and likely for the near future, is final, the end, forever. Optimism about whiz-bang research shouldn't be allowed to obscure that basic fact.