Professors at Stanford and the National Autonomous University of Mexico released a sobering study on Monday detailing the impact of human actions driving mass extinction.
“We are in the sixth mass extinction event,” begins the paper authored by researchers Gerardo Ceballos and Paul R. Ehrlich. “Unlike the previous five, this one is caused by the overgrowth of a single species, Homo sapiens.”
“The episode… is much more threatening, because beyond that loss, it is causing rapid mutilation of the tree of life,” state the authors, using English naturalist Charles Darwin’s metaphor for the living world. “Entire branches (collections of species, genera, families, and so on) and the functions they perform are being lost.”
Simple schematic representation of the mutilation of the Tree of life because of generic extinctions and extinction risks. The bottom half of the tree depicted as dead branches shows examples of the extinct genera, and the upper half shows examples of genera at risk of extinction. (Ceballosa & Ehrlich, PNAS, 2023)
“The current generic extinction rates are 35 times higher than expected background rates prevailing in the last million years,” wrote Ceballos and Ehrlich.
A number of human actions are identified as contributing to the phenomenon, including poaching, habitat loss, and pesticide use. The role of climate change is also examined, another crisis the researchers say is closely related.
"The extinction crisis is as bad as the climate change crisis. It is not recognized," said Ceballos.
A number of startling events recently demonstrated these dual crises during a summer in the Northern Hemisphere, described by NASA as the “hottest since global records began in 1880.” Rising ocean temperatures have contributed to mass die-offs observed among birds, fish, and sea lions. Recently, vanishing polar ice contributed to the collapse of entire colonies of emperor penguins in Antarctica.
An ongoing crisis regarding a decline in populations of bees and other insects has also been reported for several years.
The authors caution the consequences of extinctions are difficult to predict because the interrelations between living beings are so complex. "If you take one brick, the wall won't collapse," said Ceballos. "You take many more, eventually the wall will collapse.”
"What happens in the next two decades will very likely define the future of biodiversity and H. sapiens," the authors warn. “Immediate political, economic, and social efforts of an unprecedented scale are essential if we are to prevent these extinctions and their societal impacts.”
“People say that we are alarmist by saying that we expect a collapse. We are alarmist because we are alarmed.”