About 30 per cent of the species on a conservation watch list are at risk of extinction, conservationists say.
As they updated a red list of species most at risk, they published for the first time a green list of species that could offer hope to conservation efforts around the world.
Habitat loss, overexploitation and illegal trade continue to be the main threats to species, the International Union for the Conservation of Nature said.
Of the 138,374 species assessed by the group for its survival watch list, about 28 per cent are at high risk of vanishing for ever, it said on Saturday.
Shark and ray populations have declined since they were last assessed and more species are now threatened with extinction, the group said in its revised Red List of Threatened Species, published on Saturday.
But IUCN director general Bruno Oberle said the trend could be reversed and this year’s assessment offered cause for optimism.
“The newest assessment of these species brings us a bit of hope,” he said.
“Some of these species are recovering, slowly. Others are still threatened. But it is the demonstration that if states and other actors take the right actions on a [timetable] that is long enough, it is possible to recover.”
Fishing quotas have allowed several tuna species to set out on “the path to recovery”, the World Conservation Congress in Marseille was told.
The IUCN's new "green status" will act as a companion to the survival watch list and measures how species fight back towards historical population levels.
The initiative aims “to measure species recoveries in a standardised way, which has never been done before”, said green status co-chief Prof Molly Grace.
It was born of a realisation that “preventing extinction alone is not enough”, said Prof Grace, from the University of Oxford.
More than 180 species have undergone green status assessments so far and the IUCN hopes to one day match the tens of thousands on the red list.
They are classified on a sliding scale, from “fully recovered” through “slightly depleted”, “moderately depleted”, “largely depleted” and “critically depleted”.
When all else has failed, the final listing is “extinct in the wild".
The California condor has been classified as critically endangered for the past three decades, despite major investment in its preservation.
“Some people might think, 'We've been trying to conserve the condor for 30 years, its red list status has been critically endangered for all those 30 years, what is conservation actually doing for this species?'" Prof Grace said.
But her team found the California condor would be extinct in the wild had it not been for these conservation efforts, she said.