Large ecosystems like the Amazon rainforest could collapse in less than 50 years once a crucial tipping point is reached, a new study has claimed.
Researchers argued some natural environments are collapsing at a "significantly faster rate" than previously thought and could transform into "alternative ecosystems" when put under stress.
The study, which was based on computer simulations using real-world data from more than 40 natural environments, suggested the Amazon could shift to "a savannah-type ecosystem with a mix of trees and grass" in just 49 years.
Meanwhile, the Caribbean coral reefs, which are around 20,000 sq km in size, could become bleached and sparsely populated in just 15 years.
The researchers studied data on the transformations of four land, 25 marine and 13 freshwater ecosystems to come to their conclusions.
"Unfortunately, what our paper reveals is that humanity needs to prepare for changes far sooner than expected," Dr Simon Willcock, a joint lead author on the study, from Bangor University's School of Natural Sciences, said.
"These rapid changes to the world's largest and most iconic ecosystems would impact the benefits which they provide us with, including everything from food and materials, to the oxygen and water we need for life."
The research used computer modelling to find that while larger ecosystems took longer to collapse, their breakdown occurred relatively quickly compared with smaller systems.
"We intuitively knew that big systems would collapse more slowly than small ones - due to the time it takes for impacts to diffuse across large distances," John Dearing, a professor of physical geography at Southampton University, who led the research, said. "But what was unexpected was the finding that big systems collapse much faster than you might expect - even the largest on Earth only taking possibly a few decades."
However, Dr Erika Berenguer, a senior research associate at the University of Oxford and Lancaster University, who was not involved in the study, said its conclusions were not supported by the data analysed.
Dr Berenguer said: "While there is no doubt that the Amazon is at great risk and that a tipping point is likely, such inflated claims do not help either science or policymaking."