Ecosystems collapse faster than thought

What happens when an ecosystem is past its tipping point?
17 March 2020

Interview with 

Simon Willcock, University of Bangor


View of amazon forest from river


Climate change is always a worry, and with it is the worry of losing the ecosystems we have around the planet, from the Amazon Rainforest to the great Barrier Reef in Australia. New research out this week in Nature Communications has shown that once an ecosystem is past a certain “tipping point”, that ecosystem will collapse faster than previously thought. Meaning that the Amazon could collapse into grassy savannah in just a few decades, once past that point. To learn more about how they came to these conclusions, Adam Murphy spoke to Simon Willcock from the University of Bangor…

Simon - What we discovered is that the size of an ecosystem relates to how long that ecosystem would take to collapse, and this isn't linear like you might expect, so that basically, a 10 kilometer forest would collapse quicker than you would expect looking at a five kilometer forest.

Adam - What did you do to pull that answer together? What kind of experiments did you do? Models did you create?

Simon - So the study is basically in two parts. The first part is simpler and much less geeky. In that part we looked at data from all across the world, of ecosystems that had collapsed. Some of these were really small, so for example, we had a lake in a park in Australia, and some of them were absolutely massive, so like the desertification of the Sahel in Northern Africa, and from this we had the dates the collapse started, the dates the collapse finished, and obviously the area of the site. So then we, from these real world data, created a pattern and saw a relationship relating the size of the ecosystem to the speed of the collapse. Then it got a bit more complicated in the second part of our study, because we'd identified this relationship, but we didn't really understand how it worked. So we built a series of computer models, modeling various systems from things like predation. Wolves eating sheep who in turn eat grass, to other models for example, of social networks. So how our rumour might spread throughout society and we use these models to try and give us some insight into why this pattern occurs.

Adam - When it crosses over that tipping point. Is there anything to do to bring it back or is it a ball rolling down a hill kind of job?

Simon - Ball rolling down the hill is a really good analogy, because you can push a ball back up the hill, but it's a lot easier to A, stop the ball rolling down the hill in the first place, or B, catch it when it's near the top because then you only have to push it a little bit uphill. If you wait and let the system collapse, and go the ball roll all the way down the Hill, then you can get it back. You just have to put in a lot more effort.

Adam - And what does this mean for ecosystems around the world right now that might be in danger like the Amazon rainforest. What does it mean there?

Simon - Our result for ecosystems across the world, means that they potentially could collapse a lot quicker than you might imagine. So in real terms, this means that we need to put in a lot more effort into ensuring that we use these ecosystems sustainably, that we're not damaging them through things like climate change or pollution. And if we are damaging them and we do detect a tipping point occurring, we need to be in a position where collectively as a society we can act quickly to address this.

Adam - Can we detect tipping points kind of in the present or is it something we'll only be able to see in hindsight?

Simon - It's a lot easier to spot them in hindsight, but you can predict them. It's just quite difficult. There are two things you can look out for in particular. One of them is called flickering, and the other one is called critical slowing down. Flickering it's much like, imagine a candle going out. If there's two states, the candle is lit, and the candle is out. When the candle is almost going out, say in a breeze, sometimes the flame goes really small, and then big again and really small and then big again. That is literally flickering, and an ecosystem does the same thing. So when it's close to a tipping point, you might have a forest, part of the forest might turn into grassland because there was a fire, and then it would recover. And then another part would do that. And the more frequent these flickers, the closer we think we are to a tipping point. Critical slowing down is where, the time, effectively it takes to recover. If the forest recovered in two years the first time it happened, but then maybe in 10 years the second time it happened, then that would also indicate you were getting closer to a tipping point.

Adam - What's next? What's the next step in this research?

Simon - There's quite a lot of unanswered questions in this research. Like personally, I'm really interested in the role that biodiversity plays in this. So we discovered a relationship that relates the size of the ecosystem, but it might also matter how many species are in those ecosystems. So potentially more biodiverse ecosystems might collapse slower or even faster. We don't really know right now, but I'd love to look into it.


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