The planet’s largest ecosystems could ‘unravel fast’

Thanks to their sheer size giant ecosystems like the Amazon’s rainforests are relatively impervious to environmental stresses compared to smaller ones. Or so we tend to think.

Yet a new study published in the journal Nature belies this assumption. A larger, more complex ecosystem may be more prone to a sudden collapse than a smaller one once it has been pushed past a tipping point by environmental and climatic factors.

A team of researchers behind the study reached this conclusion after examining the relationship between the size of an ecosystem and the speed with which it collapses in a dramatic “regime shift.” Their findings have yielded unsettling insights.

“Regime shifts can abruptly affect hydrological, climatic and terrestrial systems, leading to degraded ecosystems and impoverished societies,” the authors write. “[L]arge systems tend to shift more slowly than small systems but disproportionately faster,” they add, based on the results of five computer models.

Even in a human lifetime a vast ecosystem like that of the Amazon could come undone. Dramatic shifts in large ecosystems around the planet could “occur over ‘human’ timescales of years and decades, meaning the collapse of large vulnerable ecosystems, such as the Amazon rainforest and Caribbean coral reefs, may take only a few decades once triggered,” the scientists warn.

Initially, as can be expected, larger and biologically more complex ecosystems are more resilient than smaller and simpler ones. Yet past a point of no return, they then collapse faster as a result of a devastating ripple effect throughout their constituent parts.

A vast ecosystem like the Amazon’s rainforests could collapse in just half a century while stressed coral reefs in the Caribbean could do so in just a decade and a half.

Impressed by their scale, size and geological age, we may be fooled into thinking that large ecosystems are supremely resilient and can rebound from the ravages of environmental stresses. Yet such an illusion of permanence is deceptive, the experts warn.

“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,” they say.