How global warming caused mass extinctions TWICE in Earth’s history: Study finds they caused ocean acidity to rise and coral reefs to collapse

Mass extinction events spanning two global warming periods in Earth’s history wiped out huge amounts of ocean life and destroyed reef ecosystems, a new study warns.

It’s previously been suggested that the Late Triassic and Early Toarcian extinctions, both linked to massive volcanism and the resulting climate changes, simply intensified extinction rates that were already underway.

But according to new research, this was not the case.

An analysis of background extinction rates and those experienced during the two events suggests extinction patterns changed dramatically each time due to rising ocean temperatures, acidification, and oxygen-starved waters.

‘The data show clear differences in extinction magnitude and selectivity between the hyperthermals [extreme warming events] and background intervals,’ the authors write in a new study published to Proceedings of the Royal Society B.

The Late Triassic mass extinction (LTE) and the Early Toarcian (ETOE) extinction took place about 201 million years ago and 187 million years ago, respectively.

The latter is considered the second largest marine biodiversity loss event in Earth’s history.

According to the new research, these past warming periods and the resulting extinctions offer a glimpse at the threats posed by human-induced climate change today.

Both of these events were ‘responsible for the mass extinction of marine organisms and resulted in significant ecological upheaval,’ the paper notes.

The team modelled extinction through the Late Triassic and Early Jurassic using a global database of marine organisms.

And, this revealed profound changes that varied between the two extinction events.

Both periods experienced changes in extinction selectivity – or the types of species going extinct during that time – but the effect was more extreme during the Late Triassic.

This finding goes against the previous suggestion that there were no differences in extinction selectivity from the background rates.

The team also found some patterns that arose between the two separate events.

‘Despite differences in starting conditions, species involved, and magnitudes of global warming and environmental change, the LTE and EToE show some common patterns of selectivity,’ the researchers explain in the study.

‘Both events record strong extinction selectivity against pelagic predatory guilds and against benthic photosymbiotic and suspension feeding organisms, suggesting that these groups of marine organisms may be particularly vulnerable during episodes of global warming.’

According to the researchers, both of the warming events triggered rapid temperature increases, ocean anoxia (in which oxygen is depleted), and acidification.

This, in turn, led to the collapse of reef ecosystems.

In addition to uncovering new clues on Earth’s past, the researchers say the findings provide ‘ample warning’ about what could arise as a result of current climate change trends.

Cheyenne Macdonald, Daily Mail, 24 October 2018. Article.

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