The global effort to save some of the Earth's rarest creatures from extinction is fundamentally flawed, scientists say.
By Alex Kirby
BBC News Online environment correspondent
They have found that hundreds of endangered species live in areas which offer them no protection at all.
At this rate, they believe, many more will vanish in a few decades.
But they say there is still a chance to save most of the creatures at risk.
The alert is sounded in a report released at the World Parks Congress in Durban, South Africa, organised by IUCN - The World Conservation Union.
The report is the work of the Center for Applied Biodiversity Science (Cabs) at the US-based Conservation International, and IUCN's World Commission on Protected Areas.
In what the authors call "a global gap analysis", they set out to see how well the world's network of protected areas actually helped wildlife.
They compared a map of all the areas with others showing the ranges of more than 11,000 bird, mammal and amphibian species.
They found 260 mammals they defined as "gap species", with no protection over any part of their range: 825 amphibians fell into the same category.
All the birds they studied were threatened, and 223 of them were unprotected.
Giant jumping rat: Unprotected (Image: Olivier Langrand/Conservation International)
Many of the other gap species are no cause for worry, but 140 mammals and 346 amphibians are classed as threatened.
Additionally, the study says, many existing protected areas are so small they are virtually useless for conservation, putting at least 943 more species at risk.
Without an urgent expansion of the protected area system, the authors say, they expect "a major wave of extinctions within the next few decades".
But Gustavo Fonseca of Conservation International said: "By identifying the most urgent priorities that require protection and acting strategically and quickly, we still have a chance to save the vast majority of these species."
Mohamed Bakarr, deputy chair of IUCN's protected areas commission, said: "The single most effective way to conserve species is to maintain their natural habitats.
Much from little
"The results of this analysis must be used to identify those places on Earth where we need immediate protection."
Not surprisingly, perhaps, the study identified tropical areas, especially rainforests, and islands as the priorities for action.
Islands make up 5.2% of the Earth's land surface, but contain 45% of all the species analysed in the study, more than half of them endemic (unique to one habitat).
Caerulean paradise flycatcher: Vanishing (Image: Jon Riley/BirdLife)
The analysis concluded that modest action would yield impressive benefits: adding 2.6% of the world's land area to the protected area system would cover about two-thirds of species which at present have no protection.
Some of the creatures it identified as priorities for action cling precariously to survival.
Threatened and unprotected mammals include one of the world's rarest fruit bats, the Comoro black flying fox.
A vanishingly rare amphibian is the Wuchuan frog, found only in one cave in China.
Most of the birds which lack protection are in Indonesia and the Latin American Andes.
They include the yellow-eared parrot of Colombia, with fewer than 150 known survivors, and the even rarer caerulean paradise flycatcher, found on one Indonesian island.