A conference in Hobart has been told by a marine geophysicist that humans could wipe-out three-quarters of the Earth's species within 240 - 500 years.
Professor Mike Coffin from the University of Tasmania said on Saturday that current figures show that Earth's species are declining at a rate that could see mass extinction levels reached in 240 years.
"We're on a trajectory to reach the 75% level some time between 240 and 2,000 years from now," he said.
A mass extinction occurs when Earth loses more than 75% of its species in a geologically short time frame.
The ABC reports theere have been five mass extinctions in the past 540 million years, which were caused by asteroid collisions, climate fluctuations and volcanic eruptions.
For the first time, however, a species could be the cause of a mass extinction event.
Professor Coffin said the best estimates are that about 8.7 million species are currently alive on Earth, although scientists cannot know for sure. These numbers include viruses and bacteria.
Professor Coffin said scientists are yet to discover the vast majority of species.
"I think of that 8.7 million we think there are now, we've only (discovered) about 15%," he told ABC News Online. "So there is still 85% that are yet to be discovered and or described."