Volcanic eruptions likely resulted in an increase in global temperatures that killed off CO2-absorbing plant life. The loss of those plants caused high levels of atmospheric CO2 to remain leading to an extended period of global warming. (Adobe Stock #1445271836/by GG Kenji)

Martin Wahl

An article was published in Nature Communications and prompted a CNN report in July, “The ‘Great Dying’ wiped out 90% of life, then came 5 million years of lethal heat. New fossils explain why,” This was concerning why there was an unprecedented period of lethal heat following the third of the big five extinction events over the earth’s last 500 million years. The recovery from the Permian–Triassic Mass Extinction (PTME) was 10 million years; usually (that term is used here with some trepidation) the planet recovers from a major extinction event in a shorter period.

So, What Happened?

The peer-reviewed article, “Early Triassic super-greenhouse climate driven by vegetation collapse”, provides an exhaustive, and exhausting, review of geologic and fossil evidence from around the world coupled with extensive “climate-biogeochemical modelling.” The authors show that catastrophic volcanic eruptions likely resulted in an increase in global temperatures that killed off CO2-absorbing plant life. The loss of those plants caused high levels of atmospheric CO2 to remain leading to an extended period of global warming. As they put it:

Our reconstructions show that terrestrial vegetation loss during the PTME, especially in tropical regions, resulted in an Earth system with low levels of organic carbon sequestration and restricted chemical weathering, resulting in prolonged high CO2 levels. These results support the idea that thresholds exist in the climate-carbon system whereby warming can be amplified by vegetation collapse.

What Caused It?

Well, not human activity, since our ancestors wouldn’t be around for another 240 million years. Huge, persistent volcanic eruptions, lasting 2 million years or so in Siberia, launched CO2 into the atmosphere. Some of that CO2 originated from fossilized organisms (calcium carbonate) in sedimentary rock that was “cooked” by magma on its way to the surface. The greenhouse gas caused heating that was so severe that plants were killed off, taking 10 million years to recover.

So What?

The concern is that we are approaching a “tipping point” where simply reducing CO2 emissions will not stave off a long-term global heating period that may have catastrophic effects not just for us humans, but also for the CO2-absorbing plants that are the most important part of the carbon-management cycle. One ray of hope is that today’s forests may be more resistant to the effects of climate change than those of 250 million years ago and may therefore have an improved survival rate.