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More than the small ecosystems, it is the larger ones like Amazon rainforest and Caribbean coral reefs that risk faster collapse, according to a new study. Once triggered, such large ecosystems may experience a widespread, long-lasting change or shift at a much quicker pace than previously thought, says the study published this week in Nature Communications.

With widespread fires and destruction over the past few decades, scientists have been warning us that the ecosystems in Amazon and Australia are on the verge of a 'tipping point'. The ‘tipping point’ or the ‘point of no return’ is the threshold of an ecosystem after which they collapse and transform into an alternate ecosystem. As any ecosystem crosses this threshold, it loses its capacity to carry out its current function and support the wildlife dependent on it at present.

The new study has now demonstrated the alarming rate of breakdown, after we cross this threshold. The findings of the study show that upon reaching ‘tipping point’, the vast ecosystems of Caribbean coral reefs and Amazon rainforest could collapse in less than 15 years and 49 years, respectively.

“Unfortunately, what our paper reveals is that humanity needs to prepare for changes far sooner than expected,” says one of the authors Dr Simon Willcock of Bangor University.

The study says that once this threshold is breached, Amazon rainforest will collapse and transform into a ‘savannah-type ecosystem with a mix of trees and grass’. The findings revealed that each additional unit area of an ecosystem results in the lesser time taken for collapse. Therefore, the study proves that once triggered, large ecosystems are disproportionately more vulnerable for faster collapse than smaller ones—and given the pace of human-induced changes in these landscapes, the trigger does not seem far away.

“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. But what was unexpected was the finding that large systems collapse much faster than you might expect–even the largest on Earth only taking possibly a few decades,” says Prof John Dearing from the University of Southampton, speaking about the findings in the study.

The researchers analysed the data from 4 terrestrial, 25 marine and 13 freshwater ecosystems. The study used five computational models to estimate the importance of ecosystem structure in determining the time available for the system to transform.

Pointing out the significance of the findings, Professor Tom Crowther of Yale University, ETH Zürich, says, “The rapid shifts from one ecosystem state to another can have considerable impacts on biodiversity and can drive ecological feedbacks that can alter the climate system. This research highlights how rapidly these shifts can take place, even for large ecosystems. Understanding the rate of these regime shifts will be valuable as we aim to forecast changes in biodiversity and climate change into the future.”

The study underlines the urgency for conserving our large, yet fragile ecosystems. The authors of the study stress that we must prepare for transformations in ecosystems to occur over the ‘human’ timescales of years and decades, and not centuries and millennia.

“Humanity now needs to prepare for changes in ecosystems that are faster than we previously envisaged through our traditional linear view of the world, including across Earth’s largest and most iconic ecosystems, and the social-ecological systems that they support,” concludes the study.

Expert reaction to this study was by courtesy of the Science Media Centre, an independent venture working to promote the voices, stories and views from the scientific community to the news media.