Across the planet, rainforests are becoming savanna or farmland, savanna is drying out and turning into desert, and icy landscapes are thawing. Scientists have now recorded “regime shifts” like these in more than 20 different types of ecosystems where tipping points have been passed.
Across the globe, more than 20 percent of ecosystems are in danger of shifting or collapsing into something different.
Humans are already placing ecosystems under pressure in many different ways – what are referred to as stresses. When you combine these stresses with an increase in climate-driven extreme weather, the date these tipping points are crossed could be brought sooner by as much as 80 percent.
One possible result is that climate extremes could hit already stressed ecosystems, which in turn transfer new or heightened stresses to some other ecosystems, and so on. As a result, one collapsing ecosystem could have a knock-on effect on neighboring ecosystems through successive feedback loops: an “ecological doom-loop” scenario
To get a sense of the amount of stress that ecosystems can take before collapsing, the researchers created computer models that simulate how an ecosystem will work in the future, and how it will react to changes.
They used two general ecological models representing forests and lake water quality, and two location-specific models representing the Chilika lagoon fishery in the eastern Indian state of Odisha and Easter Island in the Pacific Ocean.
The key characteristic of each model is the presence of feedback mechanisms, which help to keep the system balanced and stable when stresses are weak enough to be absorbed.
The team used the software to model more than 70,000 different simulations. Across all four models, the combinations of stress and extreme events accelerated the date of a predicted tipping point by between 30 percent and 80 percent.
https://www.sciencealert.com/global-ecosystems-risk-collapsing-decades-before-we-predicted