Southern California Climate Has Been Stable for 50,000 Years

Research posts

The La Brea Tar Pits are among the world’s richest Ice Age fossil sites, famous for specimens of saber-toothed cats, mammoths, and giant sloths. But insects trapped in the tar pits offer an even larger—and relatively untapped—treasure trove of information. 

“Despite La Brea’s significance as one of North America’s premier Late Pleistocene fossil localities, there remain large gaps in our understanding of its ecological history,” said Anna Holden, a graduate student at the American Museum of Natural History’s Richard Gilder Graduate School and a research associate at the La Brea Tar Pits and Museum. “Recent advances are now allowing us to reconstruct the region’s paleoenvironment by analyzing a vast and previously under-studied collection from the tar pits: insects.”

 

Beetle fossil specimen with an armored shell, measuring approximately 8-10 mm.

A darkling beetle fossil from the La Brea Tar Pits.

CP image #0000 2222 9825 2094 provided by the Berkeley Fossil Insect PEN, photography by R. Romero


That analysis is starting to bear fruit, including a study published recently in the journal Quaternary Science Reviews. The study, led by Holden, examined more than 180 fossil insects from the tar pits, resulting in the most robust environmental analysis for southern California to date. That analysis shows that the climate of the region has been stable for at least 50,000 years. 

Insects adapt to highly specific environmental conditions, and most are capable of migrating when their habitats get too hot, too cold, too wet, or too dry. This is especially true for the ground and darkling beetles examined in this study, which are restricted to well-known habitats and climate ranges.

Fossils show that the same species of beetles that were present thousands of years ago are still found in the Los Angeles Basin today, a finding that reinforces previous climate work Holden has conducted on gall wasps in the region. 

 

Close-up of a beetle resting on bark.

Researchers dated beetle species from the La Brea Tar Pits that are still alive today, such as this darkling beetle.

Courtesy of J. Gross


“With the exception of the peak of the last glaciers during the late Ice Age about 24,000 years ago, our data show that these highly responsive and mobile beetles were staples in Los Angeles for at least the last 50,000 years, suggesting that the climate in the area has been surprisingly similar.” Holden said. “We hope that insects will be used as climate proxies for future studies, in combination with other methods, to give us a complete picture of the paleoenvironment of Earth.”