NEW DELHI: The world's largest tropical desert, the Sahara, has suffered a catastrophic collapse of its

, a new study has warned.

The study assessed 14 desert species and found that a shocking half of those are regionally extinct or confined to one percent or less of their historical range.

Led by the New York based

(WCS) and the Zoological Society of London (ZSL), the study was done by more than 40 authors representing 28 scientific organizations and published in the early online version of the journal Diversity and Distributions.

The Sahara, stretching 9.4 million square kilometers across North Africa, is the world's third largest desert in terms of size, though largest in the tropics. Antarctica is the largest desert followed by the Arctic region, both of which are polar, ice-capped regions.

A chronic lack of studies across the Saharan region due to past and ongoing insecurity makes it difficult to be certain of the causes of these declines, although overhunting is likely to have played a role, the WCS said in a statement.

The Bubal hartebeest is extinct; the scimitar horned oryx is extinct in the wild; and the African wild dog and African lion have vanished from the Sahara. Other species have only fared slightly better: the dama gazelle and addax are gone from 99 percent of their range; the leopard from 97 percent, and the Saharan cheetah from 90. Only the Nubian ibex still inhabits most of its historical range, but even this species is classified as vulnerable due to numerous threats including widespread hunting.

The authors say that more conservation support and scientific attention needs to be paid to deserts noting that 2014 is the halfway point in the United Nations Decade for Deserts and the Fight against Desertification and the fourth year of the United Nations Decade for Biodiversity.

"The Sahara serves as an example of a wider historical neglect of deserts and the human communities who depend on them," said the study's lead author Sarah Durant of WCS and ZSL. "The scientific community can make an important contribution to conservation in deserts by establishing baseline information on biodiversity and developing new approaches to sustainable management of desert species and ecosystems."

The authors note that some governments have recently made large commitments to protecting the Sahara: Niger has just established the massive 97,000 square kilometer (37,451 square miles) Termit and Tin Toumma National Nature Reserve, which harbors most of the world's 200 or so remaining wild addax and one of a handful of surviving populations of dama gazelle and Saharan cheetah.

There is also hope that the scimitar horned oryx may be reintroduced in the wild in the Ouadi Rime-Ouadi Achim Game Reserve, with the support of the Chadian government.