Our paleontological past allows us to see the future

2022-05-11T03:53:34.437Z

Meteorites, eruptions, glaciations... The Earth is the direct result of what happened on it. 'Ideas' previews an excerpt from the latest book by researcher Thomas Halliday

The Argentine Esperanza research station on the Antarctic Peninsular.David South / (Alamy Stock Photo)

In 1978, for the first time in world history, a human, Silvia Morella de Palma, gave birth in Antarctica.

Since then, at least ten children have been born on the mainland, most in the same settlement as the first, a small town called Esperanza, one of only two permanent civilian settlements at the end of the world.

At the time of Emilio Marcos Palma's birth, the slow migration of humans to all major land masses on Earth was complete.

Esperanza is an Argentine community of about a hundred people, a cluster of red houses in the shadow of the dark snow-capped mountains of the Western Antarctic Peninsula.

It is an active research station, populated almost entirely by families of geologists, ecologists,

Undoubtedly, this is now a human planet.

It hasn't always been this way, and perhaps it won't always, but for now, our species exerts a different influence than almost any other biological force.

The world as we see it today is but a direct result—not a conclusion or denouement, but a result—of what has gone before.

Much of life in the past has been in a stable state of existence, only slowly changing, but there were times when everything changed drastically.

Inevitable impacts of objects from space, eruptions on a continental scale, a global glaciation... omnipresent transitions that forced the structures of life to reshape themselves.

If any of those events had occurred otherwise, or had not occurred,

the future could have been very different.

Knowing the past, paleobiologists, ecologists, and climatologists can deal with uncertainty about the short- and long-term future of our planet simply by looking back to predict other possible scenarios.

Unlike other times when a single species, or a group of species, fundamentally altered the biosphere—the oxygenation of the oceans, the formation of coal swamps—ours is in an unusual position of control over the possible consequences.

We know change is happening, we know we are responsible for it, we know what will happen if it continues, we know we can stop it, and we know how.

The question is whether we are going to try.

To observe the paleontological past of the Earth is to see a range of possible consequences, a true long-term perspective.

On the one hand, life has survived 'Snowball Earth', poisoned skies, meteor impacts and continental-scale volcanic eruptions, and the recent world is as diverse and spectacular as it ever has been.

Life recovers, and extinction is followed by diversification.

This is, in a way, a consolation, but it is not the end of the story.

Recovery involves radical change and often the appearance of startlingly different worlds, but it also requires tens of thousands of years, at the very least.

This process cannot replace what has been lost.

The Esperanza community has adopted the phrase “Permanence, an act of sacrifice” as its motto.

As we have seen, in the history of the Earth there is no true permanence.

Esperanza's houses are built on rocks that demonstrate how temporary life can be: they record the shallow seas of the Early Triassic and the marine environment when the Great Dying occurred in the late Permian;

and they are littered with trace fossils, long-abandoned u-shaped burrows in the shale and the reoccupied homes of worms and crustaceans built in the sand.

The seafloor of the Bahía Esperanza formation, a series of rocks formed by suboceanic dispersions of silt, was poor in oxygen.

The reason for this fact, and the existence of similar patterns detected throughout the world,

it has been suspected for decades, but has only recently been proven.

In 2018 it was concluded that the lack of oxygen in the ocean of the Permotriassic period was undoubtedly caused by catastrophic global warming on a then unprecedented scale.

Volcanic activity in Siberia emitted enough greenhouse gases to send global temperatures skyrocketing, triggering a massive release of oxygen from the oceans, killing fish and other active marine life around the world. world.

Bacteria thrived in their absence, releasing, as a byproduct of their own respiration, clouds of hydrogen sulfide, which polluted the atmosphere and poisoned terrestrial and marine ecosystems.

Populations declined, and few survived.

The end of the Permian was the time when life—or, at least, multicellular life—came to the point of dying out.

It is an example for all of us of the worst disturbances that can be faced in an environment where mere survival depends on pre-existing advantageous associations and a dose of luck.

If we compare our world with that of the late Permian, we will find some worrying similarities.

The loss of oxygen in the oceans has not been limited to the past.

It is something that is happening today;

between 1998 and 2013, its concentration in the California Current, the main ocean current heading south off the west coast of North America, decreased by 40%.

And globally, since the 1950s, low-oxygen deep-sea areas have increased eightfold, reaching thirty-two million square kilometers in 2018—twice the area of Russia;

that is, the loss of more than a gigaton of ocean oxygen every year for the last half century.

This is due, in part,

because algal blooms are triggered more regularly by nitrogen runoff from agriculture, but also because the sea is warming, just as it was in the late Permian.

Warmer seas cause a triple problem for aerobic species.

The first is chemical: Oxygen doesn't dissolve as easily in hot water, so there's less of it to begin with.

Then there's the physical: hot water is less dense than cold, so it rises to the surface, but the heat comes from the sun, so it heats up faster, separating the warm layer from the cold depths;

these rarely mix, so dissolved oxygen does not pass to the bottom of the ocean.

And finally, we have the biological problem:

the heat makes cold-blooded animals metabolize more quickly, for which they require more oxygen, so that which has been dissolved is consumed faster.

For active animals, this triple threat spells disaster.

This isn't bad news for everyone: Bottom-dwelling organisms like crabs and worms usually survive on lower oxygen concentrations, but there's another gas present that creates a different problem.