Fossil Beetles Indicate LA Climate Has Been Relatively Stable for 50,000 Years

The new study focuses on ground beetles and darkling beetles, which are still present in and around the Los Angeles Basin today. Insects adapt to highly specific environmental conditions, with most capable of migrating when they or their habitats get too hot, too cold, too wet, or too dry. This is especially true for ground and darkling beetles, which are restricted to well-known habitats and climate ranges.

The researchers used radiocarbon dating to estimate the ages of the beetle fossils and discovered they could be grouped into three semi-continuous ranges: 28,000-50,000 years old, 7,500-16,000 years old, and 4,000 years old. Because the beetles stayed put for such a sustained period of time, evidently content with their environmental conditions, the study suggests that pre-historic Los Angeles was warmer and drier than previously inferred–very similar to today’s climate. In addition, insects that thrive in cooler environments, such as forested and canopied habitats, and are just as likely as the beetles to be preserved in the tar pits, have not been discovered at La Brea.

This is a photo of a darkling beetle fossil from the La Brea Tar Pits.

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

“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.”

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