The sixth mass extinction has claimed the passenger pigeon, Tasmanian tiger, and Baiji (Yangtze river dolphin) as some of its most well-known victims, casualties of human activities accelerating the extinction of vertebrate animal species hundreds of times faster than natural rates. However, a recent study conducted by Stanford University and the National Autonomous University of Mexico, published in the Proceedings of the National Academy of Sciences, reveals a deeper crisis. Notably, each of these three species represented the last surviving member of its genus, a higher taxonomic category. This phenomenon is not isolated; it signifies a broader “mutilation of the tree of life.”
The conventional focus on species extinctions has now been expanded in this study by Gerardo Ceballos, a senior researcher at the Institute of Ecology at the National Autonomous University of Mexico, and Paul Ehrlich, Bing Professor of Population Studies, Emeritus, in the Stanford School of Humanities and Sciences. They argue that entire genera (the plural of “genus”) are also disappearing. Ceballos warns that this trend has severe consequences, stating, “In the long term, we’re putting a big dent in the evolution of life on the planet.” Furthermore, Ehrlich emphasizes, “What we’re losing are our only known living companions in the entire universe.”
This “biological annihilation” has become evident through an analysis of conservation data from organizations like the International Union for the Conservation of Nature and Birdlife International. Ceballos and Ehrlich examined 5,400 genera of land-dwelling vertebrate animals, encompassing 34,600 species. Alarmingly, they found that 73 genera of land-dwelling vertebrates have gone extinct since 1500 AD. Birds suffered the most, with 44 genus extinctions, followed by mammals, amphibians, and reptiles.
The current rate of vertebrate genus extinction, when compared to historic rates among mammals, exceeds the past million years by 35 times. Without human influence, Earth would have lost only two genera in that time, but human actions have accelerated this to a “biological annihilation” in just five centuries.
Genus extinctions are more devastating than species extinctions, as they create significant gaps in the ecological web. When a species goes extinct, other species in its genus can partially compensate for its role. However, when entire genera disappear, it leaves a substantial void that may take tens of millions of years to regenerate through evolutionary processes. This loss of biodiversity has immediate and profound consequences for humanity, as our civilization depends on the services provided by Earth’s biodiversity.
For instance, the extinction of one genus, like the passenger pigeon, can disrupt ecosystems, leading to the proliferation of disease-carrying species like white-footed mice, resulting in human health issues such as Lyme disease. Additionally, the loss of genera means a loss of valuable knowledge and potential scientific advancements, as exemplified by the gastric brooding frog’s extinction, which could have provided insights into human health issues.
The extinction of genera also exacerbates the ongoing climate crisis since the composition of plants, animals, and microbes on Earth significantly influences climate patterns.
To address this dire situation, Ceballos and Ehrlich call for immediate and unprecedented political, economic, and social actions. They emphasize the urgency of prioritizing conservation efforts in tropical regions, which are particularly affected by genus extinctions and single-species genera. They also stress the need for greater public awareness, as the extinction crisis is deeply intertwined with the more widely recognized climate crisis. Ehrlich emphasizes the incompatibility of continued population growth, excessive consumption, and biodiversity conservation, describing it as “insane.” It’s time for humanity to take swift and comprehensive action to prevent further extinctions and the looming societal crises they entail.