The tipping point phenomenon has led to the collapse of local ecologies before, said Simon Willcock, an interdisciplinary researcher at Rothamsted Research in the UK. One good example is the Sahara Desert, which has gone from lush to dry in cycles, the most recent one possibly helped by humans.
In a paper published last month in Nature Sustainability, he and colleagues created complex models of ecosystem collapse, using two examples where tipping points happened in relatively recent history – the Chilika Lagoon in India, where fish populations collapsed, and Easter Island, where deforestation and other environmental stress led to the extinction of the local human population.
What he found, he said, was that ecological tipping points can happen much faster than previous models had shown, once they took into account multiple stresses – not just temperature changes, but factors such as overgrazing, deforestation, agricultural runoff and overfishing.
BEWARE OF NATURAL FLUCTUATIONS
Natural fluctuations – noise – also make tipping points more likely. Think of standing on the edge of a cliff, he said, with random gusts buffeting you toward and away from the brink. And consider someone nearby in still air on a similar cliff. “Who’s going to fall off the cliff first?” he asked. “It’s obvious, right?”
He also worries that too much clearing of the Amazon might dry things out just enough to start a massive fire. That would make the region drier, killing more trees, fueling more fire and lofting more carbon into the atmosphere, making the climate warmer and drier, and accelerating forest loss in a vicious cycle.
Our civilisation is delicate – our dense population centres are dependent on agriculture and lots of clean water. Although humanity survived shifts from ice ages to warm interglacial periods, our species has enjoyed an unusually quiescent period for the last 12,000 years, the point when we settled down and started farming.
A climate tipping point could make life a lot harder for our species. We’re not yet over the cliff, but we’re dancing dangerously near the edge.
Source: CNA
