How Ice Age Fossils At La Brea Tar Pits Help Us Understand Our Climate Future

More than 13,000 years ago, when an abundance of saber-toothed cats roamed the Los Angeles Basin, the giant mammal would hide in tall savanna grasses or behind juniper shrubs and stalk its prey.

“We think they were probably ambush predators,” says Emily Lindsey, associate curator and excavation site director at the La Brea Tar Pits museum and paleontology research site.

When it spotted its target — horses, camels, mammoths or other large animals known as megafauna — it would use its powerful forearms to leap out and pin down its prey.

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Then, using its 8-inch-long curved canines — serrated like a steak knife — it would slice through a vein and let the animal bleed out.

“All of that information is based on research here because we have this incredible collection of more than 2,000 saber-toothed cats,” Lindsey says. “It’s really rare that we have the whole record. You don't usually get that in paleontology.”

L.A.'s climate past and future

The La Brea Tar Pits — home to more than 3.5 million Ice Age fossils — is one of the planet’s best-kept records of what it was like in the area we now know as Southern California over the last 60,000 years. It’s also the world’s only active urban fossil dig site.

Fossils found in the asphalt help paint the picture of the life that once flourished here during the Ice Age: saber-tooth cats, giant sloths, dire wolves, grizzly bears, bison as well as juniper and oak trees.

Emily Lindsey, an assistant curator at the LA Brea Tar Pits, places a fossil inside the fossil collection room.

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But it's not just telling the story of the region’s past. This collection of Ice Age fossils also helps scientists understand what led to the most massive extinction of megaspecies on Earth since dinosaurs, when droves of large mammals suddenly died as extreme heat, drought and large-scale wildfires overwhelmed the region.

And as we endure another period of significant environmental change, these fossils also offer a window into the future.

“There was this ‘ah ha’ moment for paleontologists,” Lindsey says. “We said: ‘Oh wait, we have a really unique insight on that story because we can actually look at these different windows of different habitats from different times and see how they respond to climate change in real time.”

It’s part of a growing field called paleoecology, which aims to use the knowledge of prehistoric ecosystems that fossils yield to predict how plants and animals will respond to environmental events now and in the future.

“The fact that we have particular species of plants, or insects, or birds, or rodents can tell us a lot about how hot or cold it was, how wet or dry it was, and how that environment changed through time,” Lindsey says.

This link between the end of the Ice Age and the global warming we’re experiencing now is a focus of the ongoing research at the Tar Pits. Particularly, scientists seek to use fossil data to make decisions about how to preserve biodiversity today.

“You can only get that by looking at the fossil record,” Lindsey says.

The tar pits

About 1,000 feet beneath the metropolis of L.A. sits the Salt Lake Oil Field.
(The Los Angeles Basin is the richest in terms of oil by unit volume on earth). That, paired with the abundance of earthquakes in the region, which create cracks and chasms in the earth, paves the way for the tar pits.

Tar pits — sticky, shallow pools of asphalt that seep up through cracks and fissures in the ground — are essentially naturally occurring preservation deposits. The asphalt is so sticky that when animals stepped into it — even enormous ones like the now extinct pre-Columbian mammoth — they got trapped and couldn't get out.

Inside Tar Pit 91, where research is currently being done.

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The result? Meticulously preserved fossils that have been embalmed in asphalt for tens of thousands of years without exposure to air.

“So we get phenomenal preservation not just of bones, but of leaves and wood, insects and shells,” Lindsey says. “That’s what’s allowed us to build up the richest record of Ice Age life anywhere.”

Researchers examine fossils discovered in the tar pits.

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Using the fossil record to inform conservation decisions

Studies from Tar Pits researchers suggest extreme heat, drought and large-scale wildfires might be at the root of the last major extinction event.

Last year, a study published by researchers there found that large-scale wildfires — possibly started by humans — wiped out many of the large Ice Age mammals. The research broke new ground in an ongoing scientific debate over what triggered the Earth’s last major extinction event.

It adds more evidence to the growing understanding that extreme heat, drought and wildfires can drastically change habitats, leading to species extinction.

“This is just one example of how we can use fossil data to inform conservation and land management decisions today,” Lindsey says.

In an ongoing partnership with the Nature Conservancy, La Brea Tar Pits is now developing a practitioner's guide for land managers, mapping out ways to use fossil data in environmental decision making.

“In other words: How do you use historical and paleontological data to help inform conservation and restoration work in urban areas?” Lindsey says. “This will help address that.”

"When planning for these types of projects, The Nature Conservancy sets goals using information from a variety of sources," says Sophie Parker, director of science for climate and land use at The Nature Conservancy. "Knowing what was present at a site at multiple timepoints in the past, including the more distant past, is useful because it gives us a broader perspective on how to craft our goals."

Asphalt can be observed flowing from the gated tar pits, allowing visitors to witness the phenomenon.

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The Tar Pits also dedicates a small section of the park as the “Pleistocene Garden,” which contains plants that grew at La Brea at different times in history found in the fossil record. With plans for a major re-landscaping of the park currently in the works, there is a focus to significantly expand plants in line with the paleontological science on the grounds.

“It’s a way to viscerally communicate that story but also bring back some of those plants and serve as seed banks and help support urban nature,” Lindsey says.

Sharing the climate story

Beyond the rich scientific research backed by tens of thousands of years of fossil data, Lindsey says the most important part of the work they do at this critical environmental moment is public education.

By presenting current climate research alongside Ice Age fossil data, the hope is that it will drive a deeper understanding of our environmental crisis and emphasize a dire conclusion: then, as now, climate changes and human activities can intersect to drive large scale extinctions.

It's all laid out for the public to see in the La Brea Tar Pits museum and across its grounds.

“To have a place in the third biggest city in North America where people can see an entire scientific process," says Lindsey, "that’s another very powerful thing.”

Remains of mammoths can be seen at the La Brea Tar Pits.

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There is one notable, but perhaps hopeful, difference between then and now, Lindsey says.

The climate change that occurred at the end of the Ice Age 13,000 years ago was purely related to the earth’s orbital cycles.

Today, it’s 100% us.

“Meaning we completely have the ability to stop it if we want to,” Lindsey says. “It’s just a matter of political and societal will. I hope this helps people understand that small human actions could push the ecosystem to a tipping point.”