A study examining the status of more than 25,000 vertebrate species on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species found the number at risk of extinction was increasing.
According to the research in the journal Science, on average 52 species of mammals, birds and amphibians slide a step closer to extinction each year, moving into a more threatened category on the Red List.
But without conservation action the situation would be much worse, with an additional 20% of species moving into a more threatened category, the report estimated.
Work to conserve species has helped a number of animals turn their fortunes round, from the black-footed ferret, which became extinct in the wild before being reintroduced in the US, to the white rhino and the humpback whale.
According to information from the IUCN Red List, which assesses species on the level of extinction risk they face and considers them to be under threat if they fall into the categories of vulnerable, endangered or critically endangered, 19% of vertebrates are threatened.
The percentage of each group of invertebrates under threat ranged from 13% of birds to 41% of amphibians, the study found.
But 64 species had seen an improvement in their status as a result of work to help protect them and their habitat.
Others have not have not seen their Red List status improve as a result of conservation, but without it they would be declining - and in the case of some species, such as the black stilt, a wading bird only found in New Zealand, would have gone extinct, the study found.
Dr Simon Stuart, chairman of the IUCN's species survival commission and an author of the study, said history showed "conservation can achieve the impossible", as in the case of the white rhino in southern Africa.
But the researchers warned that long-term investment is needed to prevent species disappearing; action has been under way for 30 years to protect the golden lion tamarin and for 115 years for the white rhino.
And the current level of action is far outweighed by the scale of the threat to the world's wildlife.
Amongst vertebrates - animals with a backbone - the main threats are agricultural expansion, logging, over-exploitation and the impact of invasive alien species.
The study said that the increase in extinction risk was most marked in South East Asia where plantations of crops such as oil palm, logging for timber, conversion of land to rice paddies and hunting have all hit wildlife.
A separate report by the Zoological Society of London (ZSL) warned that it was not just threatened species which were suffering, but that common animals were also declining - with knock-on effects on services people rely on, such as pollination of crops.
The Evolution Lost report said populations of mammal, bird, reptile, amphibian and fish species had declined on average by 30% in the past 40 years.
Over the past decades, land mammal populations are estimated to have declined by a quarter, marine fish by a fifth and freshwater fish by up to 65%.
According to co-author Dr Ben Collen, of ZSL, for many species "the rates of decline are not quick enough to enter the Red List, but have very large effects on things that humans care about, ecosystem services such as pollination or fisheries where the number of fish is important".
The report also warned that entire "lineages" of species such as marine turtles and pandas are on the brink of being lost - with no similar species able to fill the ecological niches or functions they inhabit.
In the wake of the research, conservation experts called on governments meeting in Nagoya, Japan, in a bid to agree new targets for 2020 on stopping losses in the natural world to scale up efforts to conserve the Earth's biodiversity.
Global targets to reduce the rate at which species and habitats were being lost by 2010 have been missed.
Top ecologist Professor Edward O. Wilson, from Harvard University, warned: "The 'backbone' of biodiversity is being eroded.
"One small step up the Red List is one giant leap forward towards extinction. This is just a small window on the global losses taking place."
Julia Marton-Lefevre, director general of the IUCN, said: "This is clear evidence of why we absolutely must emerge from Nagoya with a strategic plan of action to direct our efforts for biodiversity in the coming decade.
"It is a clarion call for all of us - governments, businesses, citizens - to mobilise resources and drive the action required.
"Conservation does work, but it needs our support and it needs it fast."
Although the study focused on vertebrates, it also pointed to the level of threat faced by other wildlife, including seagrasses, reef-building corals and the group of seed-bearing plants known as cycads - which include conifers - that are at such a high risk of extinction that 62% are in danger.
Environment Secretary Caroline Spelman said: "This report underlines just how vital it is that the international negotiations in Nagoya succeed in agreeing new targets to protect our plants and animals.
"All species, from the threatened to the more common, play an essential role in maintaining the delicate balance of our Earth.
"Each species lost or under threat affects this balance, and can have significant economic costs in the longer term.
"I am working hard to ensure that the agreement reached in Nagoya reflects the true value of our plants and animals as well as recognising all the things that they provide us for free."
Ms Spelman, speaking from Japan, told BBC Radio 4's Today programme: "There is a strong political will amongst my colleagues, especially amongst EU countries, that we want to try and get an agreement.
"I think we can get agreement in some areas. If things are going well, we might get agreement in all of the areas."
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