Due to disruptive land management practices and human-caused climate change, fatal wildfires have increased in frequency during the past ten years. The three of us live and work in Southern California, which has been particularly hard-hit.
There was a wildfire outbreak in Southern California 13,000 years ago as well. The vegetation in the area was permanently altered by these flames, which also caused the worst extinction on Earth in more than 60 million years.
We paleontologists have a unique viewpoint on the long-term causes and effects of environmental changes, both those caused by human activity and those resulting from natural climate oscillations.
In a recent study, which was released in August 2023, we aimed to comprehend the changes that were occurring in California during the final great extinction event of the Pleistocene, also known as the Ice Age. The majority of the planet’s great mammals were wiped out by this phenomenon between 10,000 and 50,000 years ago. Dramatic climatic changes and a quickly expanding human population characterized this era.
The last major extinction
The last 66 million years of Earth’s history are referred to be the Age of Mammals by scientists. At this time, our furry forebears used the demise of the dinosaurs as an opportunity to take over as the dominant species on Earth.
Woolly mammoths, massive bears, and ferocious wolves were among the enormous animals that roamed Eurasia and the Americas throughout the Pleistocene. What is now Los Angeles was once home to five species of giant cats, three species of ground sloths, and two species of camels.
They abruptly left after that. The huge beasts that had dominated the world’s ecosystems for tens of millions of years vanished from every corner of the planet. More than 70% of mammals weighing more than 97 pounds (44 kilograms) disappeared from North America. Australia lost around 90%, and South America lost more than 80%. Today, the only places that still have what might be called “natural” animal communities are Africa, Antarctica, and a few isolated islands.
The cause of these extinctions is still unknown. Paleontologists and archaeologists have argued over plausible explanations for decades. Scientists have been perplexed not because there aren’t any obvious offenders, but because there are simply too many.
A rising climate brought about changes in weather patterns and the structuring of plant groups as the last ice age came to an end. Human populations were also expanding quickly and all over the world at the same time.
Both of these processes or one of them may have contributed to the extinction catastrophe. However, the fossil record of any place is typically insufficient to pinpoint the precise time that different large animal species vanished. This makes it challenging to pinpoint the exact cause of the problem, whether it is habitat loss, resource scarcity, natural disasters, human hunting, or some mix of these elements.
A deadly combination
Some records contain hints. The bones of thousands of huge creatures that were caught in sticky asphalt seeps during the past 60,000 years are still preserved at La Brea Tar Pits in Los Angeles, the world’s richest ice period fossil deposit. Radioactive carbon can be used to precisely date the proteins in these bones, providing researchers with a unique window into an ancient ecosystem and the chance to shed light on the timing and causes of its demise.
A cataclysmic event that occurred 13,000 years ago permanently altered Southern California’s vegetation and resulted in the loss of La Brea’s famed mega-mammals has been documented by our recent research at the La Brea Tar Pits and the neighboring Lake Elsinore.
Evidence of a fatal confluence between a warming climate interrupted by decades-long droughts and rapidly expanding human populations can be found in sediment archives from the lake’s bottom and archaeological records. These elements caused the ecosystem in Southern California to tilt over.
Our investigation discovered something new, albeit similar combinations of climate warming and human influences have been implicated in ice age extinctions elsewhere. An enormous rise in wildfires, which were likely started by people, appears to have been the driving force behind this drastic alteration.
The mechanisms that caused this collapse are still in use today. After the last ice age, as California warmed, the environment became drier and the trees shrank. Herbivore populations at La Brea decreased, likely as a result of both habitat degradation and human hunting. Tree-related species like camels completely vanished.
The lake started to evaporate as the area’s mean annual temperatures increased by 10 degrees Farenheit (5.5 degrees Celsius) in the millennium before the extinction. After that, the environment had a 200-year drought beginning 13,200 years ago. The remaining trees lost half their life. Dead vegetation accumulated on the landscape because there were fewer large herbivores to consume it.
At the same time, North America’s human population started to grow. Additionally, as they spread, individuals carried a potent new tool with them: fire.
Although fire has been utilized by ourselves and our predecessors for hundreds of thousands of years, it affects diverse ecosystems in different ways. Prior to the arrival of humans, fire activity in coastal Southern California was minimal, according to charcoal records from Lake Elsinore. But as human populations developed 13,200 to 13,000 years ago, fire in the area significantly increased.
According to our findings, the interaction of heat, drought, herbivore extinction, and human-caused fires had brought this system to a breaking point. Southern California was eventually blanketed in the thriving chaparral vegetation that emerge following fires. The famous La Brea megafauna were vanished, and a new fire regime had taken hold.
Lessons for the future
Understanding the origins and effects of the Pleistocene extinctions in California will help us better comprehend the current biodiversity and climate concerns. Today’s Southern California is experiencing a recurrence of the factors that marked the ice age extinction interval, including climate change, rising human populations, biodiversity loss, and human-caused fires.
The disturbing difference is that, primarily as a result of the combustion of fossil fuels, temperatures are rising today 10 times more quickly than they did during the end of the ice age. The frequency, intensity, and area of fires in the state of California have increased fivefold during the past 45 years as a result of this human-caused climate change.
Our research shows that fire is a very recent phenomena in this area, despite the fact that California is now well-known for its severe fires. The Lake Elsinore record reveals very little fire activity in the 20,000 years preceding extinction, even during comparable droughts. Fire does not naturally occur in the ecosystem until after humans have arrived.
Over 90% of wildfires in coastal California are still started by fallen power lines, campfires, and other human activity.
The striking similarities between the current environmental catastrophes and the megafaunal extinctions that occurred in the late Pleistocene. The past tells us that when under stress from numerous intersecting factors, the ecosystems on which we depend are susceptible to collapsing. Increased efforts to stop the release of greenhouse gases, stop careless fire starts, and protect the megafauna that still exists on Earth can help stop another, even more disastrous transition.
Emily Lindsey, Associate Curator, La Brea Tar Pits; Adjunct Faculty, Institute of the Environment and Sustainability, UCLA, University of California, Los Angeles; Lisa N. Martinez, Ph.D. Candidate in Geography, University of California, Los Angeles, and Regan E. Dunn, Adjunct Professor of Earth Sciences, USC Dornsife College of Letters, Arts and Sciences
This article is republished from The Conversation under a Creative Commons license. Read the original article.
