Around 13,000 years ago, humans and fire changed LA’s ecosystem forever

By about 11,700 years ago, most large land mammals outside of Africa had gone extinct. Scientists have long debated whether these extinctions were primarily caused either by human activities or a changing climate as the last ice age came to a close (SN: 11/13/14; SN: 2/6/14).

A new study of the remains of animals trapped long ago in the La Brea tar pits, in what’s now Los Angeles, suggests both factors worked in concert to bring about the demise of the region’s megafauna. A warming, drying climate plus humans’ hunting and burning of the landscape led to large fires that precipitated the end-Pleistocene die-offs there around 13,000 years ago and forever changed the ecosystem, researchers report in the Aug. 18 Science.