They tried to compare the forces currently reshaping the planet with the causes of those earlier planetary shifts.
They include the rapidly growing human population, which now stands at roughly 7 billion and is projected to reach 9 billion by 2045 -- a factor that didn't play into events like the previous mass extinctions or the end of the previous ice age.
That surge in population is likely to multiply the stress from land-use change, freshwater depletion and climate change, the new paper says, unless humans wean themselves from fossil fuels, reduce the amount of land and water consumed per person, and protect yet-untouched parts of the land and oceans from future development.
U.N. report points to 'irreversible changes'
Stuart Pimm, a conservation biologist at Duke University who did not contribute to the analysis, questioned the way Barnosky and his colleagues presented their results.
But Pimm agreed that the possibility of rapid, large-scale change is real.
"When you cut through all the unnecessary jargon and hype of tying this to obscure mathematics, they are saying we could be experiencing some significant changes, and they could be rapid. And they could be quite devastating," he said. "I think it's entirely plausible that could happen."
The new analysis comes as the U.N. Environment Programme issued its own report warning that Earth is undergoing unprecedented changes.
"As human pressures on the Earth system accelerate, several critical global, regional and local thresholds are close or have been exceeded," UNEP's fifth Global Environmental Outlook says. "Once these have been passed, abrupt and possible irreversible changes to the life-support functions of the planet are likely to occur, with significant adverse implications for human well-being."
The analysis, released ahead of the U.N. Conference on Sustainable Development later this month in Rio de Janeiro, examines the world's progress toward achieving 90 environmental goals that have broad international agreement.
Humanity has made significant progress on just four of those goals, the report found. Climate change is among those for which no progress has been made.
Meanwhile, there are signs of "complex, non-linear changes" already at work in parts of the world, the report says -- such as increased incidence of malaria in areas where average temperatures have crossed the threshold that encourages the spread of mosquitoes that carry the disease.
But the situation is not hopeless, the UNEP analysis finds. It says the world is capable of meeting sustainability targets by the middle of the next century to improve human well-being and protect the environment.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500