July 19 (UPI) -- The threat of extinction to all species on Earth may be much higher than previously thought, a new study suggests, after a biodiversity survey found that about 30% of species have been globally threatened or driven to extinction since the year 1500.
An international team of researchers surveyed a "large and diverse group" of biodiversity experts from around the world "who collectively study all major taxa and habitats in freshwater, terrestrial and marine ecosystems," according to the study published this week in the journal Frontiers in Ecology and the Environment.
The 3,331 biodiversity experts from 113 countries were asked to estimate past and future global biodiversity loss as well as rank factors that drive species to become globally threatened or extinct.
The experts, who had all published significant studies on biodiversity of their own, also ranked the drivers of global biodiversity loss and estimated its impacts on ecosystems and people.
The researchers, led by University of Minnesota associate professor Forest Isbell, compared the survey results to other sources of information and noted that the study carries importance because "decision makers often rely on expert judgment to fill knowledge gaps."
"Expert judgment has provided estimates and predictions of key unknowns in fields as diverse as nuclear power safety, volcanic eruptions, climate change and biodiversity loss," the study reads.
"The most accurate estimates and predictions come from large and diverse groups of experts, in part because expertise declines precipitously outside an individual's area of specialization."
A previous 2019 report from the United Nations compiled by just 145 experts from 50 countries found that about 12.5% of all species on Earth, or about 1 million species, were estimated to have been globally threatened or driven to extinction since the year 1500.
Isbell told the Minneapolis Star-Tribune that the estimate provided by the survey may differ from previous estimates because it takes into account less studied species such as insects.
"Experts also acknowledged substantial uncertainty around their estimates, with perhaps as few as 16% or as many as 50% of species threatened or driven extinct over this time," Isbell noted in a press release.
Akira Mori of the University of Tokyo in Japan, a co-author of the paper, said that the study is "unprecedented" because it brought together such a large group of regional experts from around the world.
The study also made a number of conclusions consistent with previous studies, including identifying human land-use changes and overexploitation as top drivers of global loss for commonly studied land-based species while overexploitation and climate change were drivers for the loss of marine life.
For other commonly studied species like amphibians, reptiles and birds, changes in how humans use the land and sea were the most important drivers for biodiversity loss.
Meanwhile, climate change and pollution were found to be the top drivers for biodiversity loss for species less commonly studied such as aquatic invertebrates and microbes.