Deforestation could eventually wipe out 40 per cent of trees and terrestrial animal groups if protected areas fail in the tropics, according to disturbing new research.
The study, published on Tuesday in the scientific journal Proceedings of the National Academy of Sciences, also warns of the "very real possibility" numerous rare species extinctions have already happened.
Author Associate Professor John Alroy, from Sydney's Macquarie University, says the predictions should be considered conservative.
"Tropical forests are tremendously valuable and they're much more fragile than I anticipated I would find," he told AAP.
The research drew on data from hundreds of local-scale studies and is the first of its kind.
It divided the works between those examining areas of pristine forest and cases of disturbed forests before comparing the results to show projected global species losses.
Prof Alroy said small and non-flying species were at higher risk, including frogs, lizards and insect groups.
He said the "frightening" suggestion of a mass extinction having already occurred highlighted a need for more research.
"I think that's a very real possibility," he said.
"Right now, we don't know and we should be very worried about that. It's very disturbing."
The researcher was also surprised to find his study was the first to use the "innovative" projection methodology.
"The reason this hasn't been done is the literature has mostly written by field ecologists who think about their little part of the world," he said.
"They just don't tend to think in terms of global species pools."
The study considered only disturbances from logging, when in reality other influences such as global warming, hunting, pollution and invasive species could also accelerate the process.
For this reason, Prof Alroy said the results represented "a best case scenario of the worst case outcome".
