‘Critical transition’: Earth’s chemistry fluctuated during the five largest mass extinctions

Life on Earth, from simple microorganisms that evolved and diversified to the incredible breadth of species living today, has always been turbulent.

Mass extinction events seem to occur without warning, wiping out countless species and allowing others to take their place.

But it’s not just disasters like giant volcanoes asteroid Effects that cause mass extinctions.

new research He suggests that around the time of five of the largest mass extinction events on record, Earth’s chemistry “fluctuated.”

Hindsight is a warning sign of the coming change.

The new study published in Nature CommunicationsIt shows that Earth’s climate occupied five distinct climate regimes separated by sharp transitional periods of rapid environmental change over the past 539 million years.

During these transitional periods, scientists have found that life on Earth was particularly vulnerable to mass extinction, offering a new historical explanation for why some time periods were characterized by such extreme loss of biodiversity.

The research describes a measure of overall “biosphere vulnerability” — combining rates of origination and extinction with standing biodiversity — which indicates whether or not Earth is in a period where mass extinctions are more likely.

This measure of biotic stress “increases when we have increases in extinction rates and origination rates that also represent a driver of adaptation to new and challenging conditions,” study co-author Andrei Spiridonov, a paleontologist and Earth systems scientist at Vilnius University in Lithuania, told ScienceAlert.

“It also increases when diversity decreases, which also reflects diminishing biotic potential. It should be noted that vulnerability is a collective measure, and when the state of the biosphere is weak, it does not mean that each individual species or even a region of the world is ‘stressed’.”

If you want to dig deeper into the math, the Biosphere Vulnerability Index itself is a simple formula calculated from the natural logarithm of the total density of total turnover—the combined rates at which species arise and go extinct, relative to uniform standing diversity.

In brief, it compares the rate of environmental change to overall biodiversity to indicate whether or not an ecosystem is unstable and therefore vulnerable to more drastic changes.

Putting the index to the test, the researchers found that overall vulnerability varied across the five time periods they identified, each of which lasted from 10 to more than 100 million years.

During these time periods — researchers called them “haggis boxes” because some of their graphs remind them of the Scottish dish — vulnerability to extinction and biodiversity loss largely linked to rising temperatures increased.

They found that eras of higher temperatures tend to coincide with greater biosphere weakening.

But the vulnerability of the biosphere rose dramatically as one period ended and another began – instead The “Big Five” mass extinctions. It was also associated with peak vulnerability.

Spiridonov said this does not mean that environmental disturbances cause mass extinction. For example, we know that in some of these cases, another event e.g Huge asteroid impact He was involved.

But they show that these shifts could serve as a warning sign that life on Earth will temporarily be more fragile than usual, and more vulnerable to another coming catastrophe.

When a system approaches a critical transition, he said, it provides information “about possible futures involving imminent major changes, such as a mass extinction or even a series of them.”

What does that mean for today?

The study provides a historical analysis, as it cannot predict what will happen to humanity or other species currently on the move The ongoing climate crisis and Period of accelerated extinction.

Related to: The largest mass extinction on Earth reveals terrifying similarities to today’s world

“Our study indicates that the current geological era – the Cenozoic – is exceptionally stable with low vulnerability,” he explained.

“This does not mean that the external influence of geophysical forces or human influence would not have had any significant effects on the evolution of the biosphere. It only means that under different background conditions, which have prevailed in other geological eras, such a disturbance would have had a much greater impact.”

The research was published in nature.