Warnings of global ecological tipping points may be overstated
There's little evidence that the Earth is nearing a global ecological tipping point, according to a new Trends in Ecology and Evolution paper that is bound to be controversial. The authors argue that despite numerous warnings that the Earth is headed toward an ecological tipping point due to environmental stressors, such as habitat loss or climate change, it's unlikely this will occur anytime soon—at least not on land. The paper comes with a number of caveats, including that a global tipping point could occur in marine ecosystems due to ocean acidification from burning fossil fuels. In addition, regional tipping points, such as the Arctic ice melt or the Amazon rainforest drying out, are still of great concern.
"When others have said that a planetary critical transition is possible/likely, they've done so without any underlying model (or past/present examples, apart from catastrophic drivers like asteroid strikes)," lead author Barry Brook and Director of Climate Science at the University of Adelaide told mongabay.com. "It’s just speculation and we’ve argued [...] that this conjecture is not logically grounded. No one has found the opposite of what we suggested—they’ve just proposed it."
According to Brook and his team, a truly global tipping point must include an impact large enough to spread across the entire world, hitting various continents, in addition to causing some uniform response.
"These criteria, however, are very unlikely to be met in the real world," says Brook.
The idea of such a tipping point comes from ecological research, which has shown that some ecosystems will flip to a new state after becoming heavily degraded. But Brook and his team say that tipping points in individual ecosystems should not be conflated with impacts across the Earth as a whole.
Even climate change, which some scientists might consider the ultimate tipping point, does not fit the bill, according to the paper. Impacts from climate change, while global, will not be uniform and hence not a "tipping point" as such.
"Local and regional ecosystems vary considerably in their responses to climate change, and their regime shifts are therefore likely to vary considerably across the terrestrial biosphere," the authors write.
Barry adds that, "from a planetary perspective, this diversity in ecosystem responses creates an essentially gradual pattern of change, without any identifiable tipping points."
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Deforestation image via Shutterstock.