(CNN) -- A fifth of the world's vertebrates are facing extinction because of invasion and the effects of agriculture, a global study warned Wednesday.

The number of species facing extinction is rising, according to scientists, but conservation efforts are helping reduce the overall rate.

"The backbone of biodiversity is being eroded," said Edward O. Wilson, a professor and ecologist at Harvard University. "One small step up the Red List is one giant leap forward towards extinction. This is just a small window on the global losses currently taking place."

Scientists launched the study, dubbed the Red List, at the United Nations biodiversity summit in Nagoya, Japan, where talks on protecting the environment are under way.

U.N. summit sends S.O.S. on biodiversity

The study, which will also be published in the journal Science, found that at least 41 percent of amphibians are closer to extinction, making them the most threatened animals.

Thirteen percent of birds qualify to be on the list.

Scientists used data from 25,000 species to study the world's mammals, birds, amphibians, reptiles and fish.

"On average, 50 species of mammal, bird and amphibian move closer to extinction each year due to the impacts of agricultural expansion, logging, over-exploitation and invasive alien species," the report says.

The study singled out 64 mammals, birds and amphibian species whose status has improved, including three species once considered extinct that have made a comeback amid conservation efforts. They are the California Condor and the black-footed ferret in the United States, and the Przewalski's horse native to Mongolia.

Southeast Asia had the most losses because of rapid expansion of palm oil farms, timber operations and rice crops, according to the study. A deadly fungus that affects amphibians contributed to losses in parts of Central America, the tropical Andes of South America and Australia.

The study confirms other reports of continued losses in biodiversity.

However, the scientists say it's the first to present evidence of the effects of conservation efforts worldwide.

"Results show that the status of biodiversity would have declined by nearly 20 percent if conservation action had not been taken," the report says.