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One in five countries at risk of ecosystems collapsing — here’s what that might look like

November 29, 2020 in Blogs

By The Conversation

Anna LoFi/Shutterstock

John Dearing, University of Southampton

One in five countries are at risk of their ecosystems collapsing, threatening more than half of global GDP (US$42 trillion, or £32 trillion), according to recent research. This scary sounding statistic raises all sorts of questions. What does “ecosystem collapse” actually mean? What causes an ecosystem to collapse and how do we know when it’s happened? Perhaps most important of all, what comes next?

Ecologists use the term “collapse” to describe a process resembling a failed soufflé or a burst football. When ecosystems collapse, they rapidly lose their structure and function, with dramatic changes to their size or extent, or the species that comprise them. These losses tend to homogenise and simplify the ecosystem – fewer species, fewer habitats and fewer connections between the two.

Read more:
Live fast, die small: how global heating is simplifying the world’s ecosystems

Controlling the collapse

When mature forests collapse, they usually transition to more open woodland with scrub and grasses, depending on the grazing animals present and the climate. A vibrant coral reef becomes an ossuary of rubble, which slowly wears away. In kelp forests where sea otters have been hunted out, unchecked sea urchins can overrun the seaweed, creating a desolate plain with few species known as

On the left, a vibrant kelp forest. On the right, the aftermath of sea urchin overgrazing.

Andrew B Stowe & Zaferkizilkaya/Shutterstock

These changes effectively mean that the original ecosystem has become locally extinct. The services which it might previously have supplied – food, carbon storage or water filtration – are lost or diminished. But “collapse” remains a vague term, as the causes and final outcomes differ from ecosystem to ecosystem.

For humans, not all ecosystem changes are bad or recent. People have relied on modifying ecosystems for millennia – draining wetlands, damming rivers, felling forests – to create new farmland. These environments are maintained in an artificially collapsed state for the benefit of maximising a particular form of food and fibre.

They could collapse further if, for example, wind and rain eroded enough soil to shift farmland to a barren state with little or no ecosystem services – think the Dust …read more


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