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100 most endangered species listed with this question: Are they worth saving?

Jessica Bryant / Zoological Society of London

The Hainan gibbon, a native of China's Hainan Island, was among the 100 most endangered species cited in a new report. Fewer than 50 of the apes are left.

Priceless or worthless? That's the question posed in a report released Tuesday that lists the 100 most endangered animals, plants and fungi around the globe, as chosen by 8,000 experts for the Zoological Society of London and the International Union for Conservation of Nature (IUCN).

The question was raised because the species closest to extinction don't have an obvious economic value to mankind and yet some, especially the experts, would argue for their protection.

"The donor community and conservation movement are leaning increasingly towards a 'what can nature do for us' approach, where species and wild habitats are valued and prioritized according to the services they provide for people," Jonathan Bailie, conservation director at the Zoological Society of London, said in a statement issued with the report.

"This has made it increasingly difficult for conservationists to protect the most threatened species on the planet," he added. "We have an important moral and ethical decision to make: Do these species have a right to survive or do we have a right to drive them to extinction?"

Craig Turner / Zoological Society of London

The pgymy three-toed sloth is native to an island off Panama. Fewer than 500 are thought to be left.

The species are native to 48 countries, but their names don't always shout out "Save me" -- among them the pygmy three-toed sloth (found only on an island off Panama and fewer than 500 are left); the Hainan gibbon (fewer than 20 are left on China's Hainan Island); and the willow blister (a fungi found in Wales).

The report doesn't estimate the cost of saving the 100 species, nor does it rank them, instead listing them alphabetically by their scientific name -- starting with Astrochelys yniphora, or ploughshare tortoise.

"Having narrowly survived hunting pressure and habitat destruction by fire in the past, this species’ good looks may be its ultimate downfall as illegal collection for the international pet trade is likely to push it to extinction in the wild in the near future," the report states.

The Japanese otter was declared extinct today by the Japanese government after not being spotted for over 30 years. NBCNews.com's Richard Lui reports.

Fewer than 770 ploughshare tortoise are thought to survive in the wild of their native Madagascar.

The experts noted that the 100 species chosen are just a fraction of the thousands of species that also face extinction, just perhaps not as soon.

"The future of many species is going to depend on reconciling the needs of people and nature, and ensuring economic development and conservation do not undermine each other," Simon Stuart, chair of the IUCN's species survival commission, said in a foreword to the report.

"If we ignore the question" about priceless or worthless, he added, "we shall be inadvertently accepting the ethical position that human-caused mass extinction is acceptable."

The World Wildlife Fund framed the issue slightly differently.

"Ideally, we would try and save every species on the planet because everything in nature is connected and so are the solutions to environmental problems," Sybille Klenzendorf, WWF's species conservation director, told NBC News. "However, since saving every single species would be an enormous undertaking, we must focus our efforts on conserving nature as a whole.

"For WWF, that means working on what we call umbrella species like tigers, elephants and rhinos," she added. "By focusing on conservation of those species, we’re also aiming to protect other species that share their habitat -- or are vulnerable to the same threats."

Cristian Samper, head of the New York-based Wildlife Conservation Society, agreed on that approach.

"We won't be able to save every species, but if we are smart we can save many of them," Samper said. "We focus on places where you have many species and big threats."

"In extreme cases," Samper said, "we will save species in zoos and aquariums and then reintroduce them, like we did at the WCS Bronx Zoo with the American bison a hundred years ago and we are doing that now with turtles and frogs today."

Galapagos tortoise Lonesome George has died. The only remaining Pinta Island giant tortoise-believed to be the last of his species- was believed to be about 100 years old. ITV's Annabel Roberts reports. 

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