By Alister Doyle

OSLO (Reuters) - Obscure flora and fauna that few people have ever heard of such as the Jamaican rock iguana need to be much better protected if the world is to achieve a goal of preventing species dying out by 2020, a study said on Tuesday.

The report, "Priceless or Worthless?", listed the 100 most threatened species and said critically endangered plants and animals such as Tarzan's chameleon in Madagascar merited conservation since they were irreplaceable for the Earth even if they had no economic value for people.

"Over half (of the 100 most endangered species) are receiving little or no attention," Professor Jonathan Baillie, Director of Conservation at the Zoological Society of London (ZSL), told Reuters by telephone from South Korea.

Few people fretted about the fate of the Singapore freshwater crab, Ethiopia's liben lark, the Seychelles sheath-tailed bat or the Luristan newt, found in only in the Zagros mountains in Iran, he warned.

And Tarzan's chameleon, colored bright green and yellow, was largely ignored in a shrinking patch of rainforest.

"We need a rethink" of conservation priorities, Baillie said of the 124-page report issued by the ZSL and the International Union for Conservation of Nature (IUCN), which is meeting in South Korea and groups governments, scientists and activists.

The IUCN said the report "hopes to push the conservation of 'worthless' creatures up the agenda that is set by NGOs (non-governmental organizations) from around the globe." Creatures such as lions or pandas get much more attention than newts, it said.

Loss of habitat, caused by a rising human population and other factors such as expanding cities, deforestation, pollution and climate change, are driving more and more species of animals and plants to extinction.

BILLIONS NEEDED

"We need a fund to prevent extinction, resourced by governments, that is in the billions, not millions," the report said, without specifying a currency.

Measures such as an expansion of protected areas or hunting bans were needed, it said.

Baillie said people may have gone too far in recent years in judging animals and plants by the economic value of the services they provide, including food, medicine or as tourist attractions.

"We need to keep the appreciation for the wonderful diversity of life on Earth as the key message, and then other utilitarian arguments have to be additional," he said.

Governments agreed in 2010 to a plan to protect life on earth that included the goal: "By 2020 the extinction of known threatened species has been prevented and their conservation status, particularly of those most in decline, has been improved and sustained."

The IUCN said that all species had value.

"Although the value of some species may not appear obvious at first, all species in fact contribute in their way to the healthy functioning of the planet," said Simon Stuart, Chair of the IUCN Species Survival Commission.

The list of the 100 most endangered species included others such as the Cayman Islands ghost orchid, the Javan rhino and the suicide palm of Madagascar, which dies exhausted after producing tiny yellow flowers on a stem up to 5 meters (16 ft) long.

The report said that past conservation efforts had helped.

A ban on hunting had helped the recovery of the humpback whale, now estimated to number 60,000. Captive breeding meant that Przewalski's horse, once almost extinct, now numbered more than 300 in the wild from Ukraine to China.

(Reporting By Alister Doyle; Editing by Andrew Osborn)