In pictures: World's most threatened species

Species such as Tarzan's chameleon are on the verge of extinction, though focused conservation efforts may save them.

International conservation groups have unveiled a list of the world's 100 most threatened animals, plants and fungi, stressing that urgent action is required in order to protect them from extinction.

The groups identified the species in a report presented to a global conservation forum being held on the South Korean island of Jeju on Tuesday.

The species live in 48 countries and include the Tarzan's chameleon, the spoon-billed sandpiper and the pygmy three-toed sloth.

The Zoological Society of London (ZSL) and the International Union for Conservation of Nature (IUCN) fear the 100 species will die out because they do not provide humans with obvious benefits.

Experts say that focused conservation efforts can prevent the species' extinction in almost all cases.

"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 prioritised according to the services they provide for people," said Professor Jonathan Baillie, ZSL’s Director of Conservation.

"This has made it increasingly difficult for conservationists to protect the most threatened species on the planet. 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?"

Ellen Butcher, a co-author of the report, said that if immediate action were taken, the threatened species could still be given "a fighting chance for survival".

"But this requires society to support the moral and ethical position that all species have an inherent right to exist."

Among the threatened species are the pygmy three-toed sloth (currently only found on an island off the coast of Panama), the saola (an antelope also known as the Asian unicorn due to its rarity) and the willow blister (a brightly coloured fungus now found only in a small area of Wales).