There are lots of tipping points in ecosystems and the climate, and many are interconnected. That means the massive changes we are wreaking will have many unexpected consequences.
“The world is a much more surprising place then generally assumed,” says Garry Peterson of the Stockholm Resilience Centre in Sweden. As an example, in 2016 the retreat of a glacier in Canada led to a river changing direction.
Peterson’s team has analysed 300 ecosystems with potential tipping points or regime changes. For instance, as rainfall increases grasslands can suddenly turn into forests, and vice versa.
The study suggests that almost half of them are linked. For example, more extreme rainfall from global heating can greatly increase soil erosion, especially on degraded farmland, and carry more phosphorus into rivers, lakes and the sea. This can trigger algal blooms and red tides, and amplify the decline in oxygen that occurs as waters warm. This leads to even bigger aquatic “dead zones” with low oxygen, which can have further knock-on effects.
What the team’s work shows is that crossing one tipping point increases the risk of crossing another and so triggering a whole cascade of effects. And we may not even recognise the danger until it is too late, Peterson says.
Take the West Antarctic ice sheet, which will raise sea level three metres if it melts. The idea that we might be nearing the tipping point beyond which it will collapse was ridiculed when it was suggested in the 1970s. Now it appears we’ve already passed the tipping point.
Scientists specialise in narrow areas and often fail to spot the connections between different earth systems, Peterson says. We also assume the future will be more or less a continuation of what’s happening now. Computer modellers often specifically exclude things that lead to sudden, discontinuous changes because they make the models too unstable. That is a serious mistake, he thinks.
“We should be preparing for a much more unstable future.”
Journal reference: Science, DOI: 10.1126/science.aat7850
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