The increasing rate of extinction today and how it affects our future

Vertebrates on the brink as indicators of biological annihilation and the sixth mass extinction

By: Gerardo Ceballos, Paul R. Ehrlich, and Peter H. Raven

Summarized by: Melody Farley, an undergraduate geology student at the University of South Florida in her final semester. Her goal is to use her degree at the Southwest Florida Water Management District to help with the management of water resources in Florida’s systems. She plans on attending graduate school in a few years, after gaining some work experience to determine what she wants to specialize in. When she is not studying geology, she loves to kayak, hike, and enjoy nature with her fiancé.

What data were used? Data was collected from the International Union for Conservation of Nature (IUCN); specifically, the number of individuals in each vertebrate species, as well as the number of species whose endangerment status has been studied was used here.

Methods: This study used the database material from the IUCN to help classify the species studied based on geographical range and number of individuals. From this, they determined the number of vertebrate species with fewer than 1,000 individuals, excluding extinct species. 

Results: 515 vertebrate species were discovered to have fewer than 1,000 individuals, indicating that they are “on the brink” and very susceptible to extinction. This comprises 1.7% of the total terrestrial vertebrate species. Of the 515 vertebrate species on the brink, more than 50% of these species have fewer than 250 individuals, meaning that there are much closer to extinction. Species on the brink are found to be concentrated in regions with higher human interaction. 543 species have gone extinct since 1900. If the 515 species were to join the 543 species that have already gone extinct, the total extinct species in a 150-year span would be 1,058 vertebrate species. Given the last 2 million years’ background rate of extinction, 9 species would be expected to go extinct in this 150-year period. So, the extinction rate would be 117 times faster than previous background rates.

Figure SEQ Figure \* ARABIC 1: This figure shows the population sizes of 5 groups – Mammalia, Aves, Reptilia, Amphibia, and Vertebrates from left to right, with Vertebrates being an aggregation of the first 4. They are categorized by the number of individuals left in the species. Here, you can see that in all 5 groups, at least 50% of the on the brink species have fewer than 250 individuals.

Why is this study important? This study is important because it illustrates the effects that humans are having on different populations around the world. Extinction rates are much higher now than in geologic history, mostly since the development of agriculture approximately 11,000 years ago. Many of the extinction rates have increased even more since the 1800s as human civilizations have become more advanced, showing that an increased competition for resources have expedited the extinction rates in recent history. 

The big picture: Earth’s systems are all part of an important balance. When a species goes extinct and disappears from an ecosystem, simple maintaining services of this ecosystem can be disturbed. If this happens enough times, we could have the collapse of ecosystems that we rely on for survival. Humans require several things to survive: a stable climate, fresh water, crop pollination, and more. Many of these are made possible by healthy and sustained ecosystems. With the continued risk of climate change, species extinction is a bigger problem now than ever, and it is important for humans to consider the effects of their development, and what this means for the future of civilizations.

Citation: Ceballos, G., Ehrlich, P.R., Raven, P.H., “Vertebrates on the Brink as Indicators of Biological Annihilation and the Sixth Mass Extinction.” Proceedings of the National Academy of Sciences, vol. 117, no. 24, 2020, pp. 13596–13602.,