Animals Spurred Earth’s First Ever Global Warming Event

Long before humans have made their mark on the planet, animals ushered in Earth's very first brush with global warming, a new study says.

It eventually caused a series of mass extinction event during animals' first 100 million years on the planet.

Discovering The Role Of Animal Evolution In Global Warming

The study published in the journal Nature Communications reveals that the evolution of burrowing animals during the Palaeozoic period sparked global warming by altering the biogeochemistry of the ocean and the atmosphere.

Animal life turned up in the ocean 520 to 540 million years ago, dramatically changing the world around them. In the process of the organisms breaking down the organic material in the ocean, more carbon dioxide was pumped into the atmosphere and less oxygen.

"Like worms in a garden, tiny creatures on the seabed disturb, mix, and recycle dead organic material — a process known as bioturbation," Tim Lenton, a professor from the University of Exeter, says in a press release from the university.

"Because the effect of animals burrowing is so big, you would expect to see big changes in the environment when the whole ocean floor changes from an undisturbed state to a bioturbated state."

How The Team Reached A Conclusion

The researchers discovered a significant decrease in the ocean's oxygen levels about 520 million years ago. This led some scientists to hypothesize that early animals had an impact in warming the world.

However, rock records showed that the sediment wasn't very disturbed, which meant animals didn't dive too deep into the seabed. Thus, many assumed that whatever effect these creatures had must have been minimal.

The new study confirms that the early animals actually had an extremely large impact on global warming.

"The critical factor was to realise that the biggest changes happen at the lowest levels of animal activity," says lead study author Dr. Sebastiaan van de Velde of the Vrije Universiteit Brussel.

Dr. de Velde explained that the realization meant that the first bioturbators played a huge role in changing the environment.

After constructing a model based on this information, the team was shocked to find that the evolution of the animals didn't just cause the atmospheric oxygen levels to plummet. It also caused the atmospheric carbon dioxide levels to rise to monumental heights that led to a global warming event.

The event potentially contributed to multiple mass extinctions during the first 100 million years of animals on Earth.

Déjà Vu?

Lenton sees a strange parallel between the way early animals changed the world and the way human animals are currently altering the planet and making it hotter.

"Essentially, we are doing the same thing as these early animals by oxidizing organic matter on a global scale," explains co-author Benjamin Mills, a researcher from the University of Leeds. "However, the events of the Cambrian occurred over millions of years, and still appear to have made life difficult for the biosphere of the time."

Humans, he points out, are doing this on a much shorter timescale, leaving little time for the planet's natural systems to kick in and stabilize the climate.