On average, 52 species of mammals, birds and amphibians are taking a significant step toward extinction each year, a huge new analysis says.

But if not for conservation efforts, the march would be even faster, researchers reported Tuesday.

Efforts to save endangered animals are making a difference, even as about 1 in 5 of the world’s backboned species — mammals, birds, reptiles, amphibians and fish — are threatened with extinction, according to a study published online in the journal Science.

The report was released as delegates from more than 190 nations meet at a United Nations conference in Nagoya, Japan, to set 20 measurable targets to combat the loss of many diverse species.

“Our results should be a timely wake-up call to governments in Nagoya,” said Stuart Butchart, a study author and global research coordinator at BirdLife International. “Biodiversity is in a desperate state. Its situation is getting worse . but our results show we can turn the situation around. We just need greater political will and resources.”

The study considered almost 26,000 species of vertebrates — animals with a backbone — whose conservation status is on the “Red List” of the International Union for Conservation of Nature. It found that about one-fifth of vertebrate species are “threatened,” meaning they are close to going extinct in the near future. That ranges from 13 percent of birds to 41 percent of amphibians.

The one-fifth number isn’t much of a surprise, but the new study is the first global audit of vertebrates, said Craig Hilton-Taylor of the IUCN, a study author.

To look for trends, the authors used a statistical measure that tracks how particular species have moved among the eight categories of the Red List — an indication of improvement or worsening of their conservation status. Because of data limitations, they focused on birds, mammals and amphibians. Their results translate to an average of 52 species moving one category closer to extinction each year.

Amphibians, which include frogs and salamanders, showed the fastest decline, with mammals second. The trend was less severe for birds, but still included creatures like the green-colored Hose’s broadbill of Malaysia and Indonesia, which has suffered declines in its forest habitat.

About 1 in 6 declines in conservation status in the study resulted in extinction, the authors said. The extinctions include the golden toad of Costa Rica and a Hawaiian forest bird called the Kamao.

To study whether conservation efforts like protecting habitat or controlling predators were helping, the authors examined cases where a species’ status improved, moving away from extinction. That was the case in 68 of the 928 reclassifications they found, almost entirely due to conservation action, the authors said. Nearly all involved mammals or birds, because they have a longer and better-funded history of conservation efforts, the authors said.

Humpback whales, for example, moved from “vulnerable” to being at low risk for extinction because of protections against commercial whaling, the authors said.

In all, the researchers calculated that the overall march toward extinction would have been some 20 percent faster if no conservation steps had been taken. But they also said the true impact is much greater than their calculations could show.

“Conservation is working, it’s just not enough” at current levels, said Ana Rodrigues of the Center for Evolutionary and Functional Ecology in Montpellier, France, a study author.

Stuart Pimm, a conservation expert at Duke University who didn’t participate in the study, agreed that the results contain good news.

“A lot of those species would have been moving a lot faster (toward extinction) if it weren’t for conservation efforts,” he said. “Conservation efforts really do work, they’re just not stemming the full extent of the losses of species. The overall trend is still downhill.”

And without the nature reserves erected over the past half-century, more would be gone.

“Conservation is working, there is just not enough of it,” says study author Ana Rodrigues of France‘s Centre d’Ecologie Fonctionnelle et Evolutive. “Now is the time to scale up conservation.”

The five-decade survey of the extinction status of 25,780 vertebrate species, roughly half of all backboned animals, was released by the journal Science. Led by Michael Hoffmann of the United Nations Environment Programme, the results find that almost one-fifth of those species are threatened with extinction (from 13% of birds to 41% of amphibians) — meaning either there are fewer than 50 individuals left, or the species’ chances of extinction are 50% or greater within 10 years. The declines are mostly tied to expanding farmland, overlogging, overfishing and competition from invasive species.

Another 52 vertebrate species move closer to extinction in a typical year.

Simply by comparing 50-year population trends before and after conservation measures such as regulation and erection of preserves, however, the survey shows 18% more species would be threatened with extinction had the measures not been undertaken. Some success stories:

•Humpback whale. Now protected by whaling conventions, populations have recovered to around 80,000, from about 5,000 in the 1960s.

•California condor. Once numbering only 22, now more than 300 exist, thanks to captive breeding efforts.

•Przewalski’s Horse. Increased from 13 or 14 living in 1945 to more than 1,800 today.

“This is a really conservative estimate of conservation’s effects,” says ecologist Taylor Ricketts of the World Wildlife Fund in Washington, D.C.

“The extinction findings are in line with past reports, but finding a basic effectiveness for conservation worldwide is the bottom line news,” he says.

The results, being presented today at the 10th Conference of the Parties to the Convention on Biological Diversity (CBD), in Nagoya, Japan, mean that 193 nations have failed to meet a 1993 agreed-upon goal “to achieve by 2010 a significant reduction of the current rate of biodiversity loss at the global, regional and national level as a contribution to poverty alleviation and to the benefit of all life on Earth.” Representatives of those nations are at the meeting to discuss a new agreement on protecting species.

Economists estimate that biodiversity brings about $33 trillion in annual benefits worldwide to humanity, notes study co-author Stuart Butchart of the United Kingdom‘s BirdLife International, through cleaner water, pest consumption and other environmental benefits. “Money spent on conservation isn’t wasted, it’s cost-effective,” he says.