Who could possibly have seen this coming? Bigger temperature changes mean more ecological upheaval?
It seems pretty straightforward, but what I find interesting is that the authors frame it as a cause for some hope about our current situation:
“These findings indicate that the bigger the shifts in climate, the larger the mass extinction,” Kaiho said. “They also tell us that any prospective extinction related to human activity will not be of the same proportions when the extinction magnitude changes in conjunction with global surface temperature anomaly.”
Kaiho cites an earlier study, which claimed a 5.2°C temperature increase in average global temperature would result in a mass extinction event comparable to previous ones. Yet, based on this study’s analysis, the temperature will need to change by 9°C, and this will not appear until 2500 in a worst-case scenario.
“Although predicting the extent of future extinctions is difficult because causes will differ from preceding ones, there is sufficient evidence to suggest that any forthcoming extinction will not reach past magnitudes if global surface temperature anomalies and other environmental anomalies correspondingly change,” Kaiho said.
I hate to sound pessimistic, but I think it would be unwise to set your clock by this research. I can’t speak to the quality of the work, but while I find the research and conclusions interesting, it seems to leave out the rate of warming. While past temperature changes have occurred fairly abruptly, I’m not aware of a warming event that happened at this rate, even if the number at which it stops is lower than those worse extinctions.
In addition to only looking at the scale of change, they also only look at temperature. That’s fine as far as it goes, but it doesn’t account for human habitat destruction, over-fishing, and chemical pollution, all of which have been taking their own toll on the resilience of the biosphere. Maybe I’m missing something about past climate shifts, but I’m reasonably certain that none of them had a mix of factors even resembling the nightmare we’re confronting.
Regular readers will know that I put a fair amount of time and effort into hope and excitement as motivation, rather than fear. I try to make this blog a place that faces the terrifying reality of what’s happening, while also holding on to enough hope and happiness that we can keep working to make things better. I clicked on this research because I was hoping it would give me genuinely good good news to share, but I’m honestly more worried that this will be used to claim that global warming isn’t an urgent issue.
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Even if we were doing nothing else the deprovincialisation resulting from human activities would generate an extinction pulse, though perhaps one of a sort that wouldn’t be recognisable in the fossil record, as it’s island endemics which are the major victims. On the other hand the spread of pathogens does have effects that would be seen – such as drastic falls in the amount of elm (in western Europe) and chestnut (in North America) pollen.
Two immediate things that occured to me when reading this:
1) Previous extinctions did not feature anthropogenic ecological and environmental damage; and
2) A 500-year timeframe? Really?
[even before AGW we were killing the fishies of the sea and the birds of the air and the insects and the forests and fragmenting habitat refuges and polluting and all that sort of stuff. And doing it quickly, just like the warming. Not really comparable]
Honestly, I’m a little tempted to dig into the authors and institutions involved, and see if there’s a money trail to follow…
Big thing here is that the current (and projected) temperature anomalies are small relative to the big 5 mass extinctions, so my read is that the paper is showing that projected climate change impacts are going to have small impacts relative to the big 5 events. This is _not_ a reason for hope given the scale of the big 5 (the vast majority of terrestrial life on earth was wiped out at the end of the Permian for example….).
Given the small dataset (only 5 mass extinctions), any projection that a 9degree change in temperature is needed to cause mass extinction is unbelievable. A good example of a paper where the discussion goes way beyond what the data says (and where the press release just pulls out that juicy bit).