Published in the journal Science, the peer-reviewed study breaks new ground in a decades-long scientific debate over what triggered the Earth's last major extinction. Supported by the precise dating of fossils preserved at La Brea Tar Pits, the research advances our understanding of the dynamics between dramatic environmental change, human population growth, wildfire activity, and the abrupt disappearance of Ice Age megafauna.
"The significance of this research will resonate for decades well beyond the scientific field," said Dr. Lori Bettison-Varga, President and Director of the Natural History Museums of Los Angeles County. "La Brea Tar Pits is the only place on Earth that has the fossil record necessary to examine the last significant climate change event in this way. The site's collection of millions of Ice Age fossils provides a unique opportunity to study environmental change.
The study laid out a disastrous chain of ecological events reconstructed from climate, vegetation, and fire records preserved in the sediments of nearby Lake Elsinore. It started with the gradual warming and drying of the landscape and a simultaneous decline in forest-adapted large herbivores over 2,000 years, as Earth emerged from the last Ice Age and glaciers receded. Then, just as human populations began to sharply increase in North America, the ecosystem underwent a dramatic change: temperatures rose rapidly, a 200-year-long drought parched the landscape, and massive wildfires transformed plant communities. Within 300 years, all the Ice Age giants at La Brea were gone, and California's modern, fire-adapted chaparral ecosystem had appeared.
Understanding the relationship between environmental change and human activity is equally important to current-day challenges, the study said. It noted that temperatures in Southern California have risen faster in the last century than they did during the late Pleistocene. Land area burned by wildfire in the western U.S. has increased four-fold in the past 20 years, and this pattern is only predicted to worsen in coming years.
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