“The world is, and always has been, in a state of flux.” With this simple phrase, the IUCN –International Union for Conservation of Nature– began its 2007 report with data regarding endangered species featured on their Red List. Perhaps the brevity of our existence causes us to forget, but this phrase reminds us that we live on a dynamic planet. One with several natural processes such as the natural selection of species and the collision of tectonic plates under our feet. Extinction is also a process such as these that is imperceptible, but that occurs continuously and constantly.
Despite this, the fossil record warns us that this is not always the case and that during different parts of Earth’s history there have been great mass extinctions. According to paleontologists, for a great mass extinction to occur, more than 75 percent of the species present must be lost in a short period of time. According to them, this has occurred 5 times in the last 540 million years due to different natural disasters. We will not stop to name them all, but we will cite the most recent, and perhaps the best known, which led to the extinction of the dinosaurs during the Cretaceous period due to the impact of a meteorite.
The story is well known by all and it’s comprehensible that a collision like this could cause such drastic changes on the planet that 76 percent of the biodiversity of the time was eliminated. However, are mass extinctions always caused by such obvious events? Is it possible that we are facing a sixth extinction where an invisible meteorite is colliding with our planet and destroying our current biodiversity?
Are we facing the sixth mass extinction?
Back in 2011, the journal Nature published ´Has the Earth’s sixth mass extinction already arrived?´ an article which presented a detailed comparative study using data analysis of the extinction rate of past processes, examining the possibility that one is currently taking place today. The conclusion of this article was clear; the current extinction rate was higher than expected based on the fossil record. However, later on, another study would be published that would be decisive in confirming this idea.
In 2015, the journal Science Advances published an article entitled: Accelerated modern human – induced species losses: Entering the sixth mass extinction.´ In this illuminating article, the authors conducted exhaustive analysis of the data provided by the IUCN on the extinction of vertebrates since 1500. The results of the work were devastating: according to this information, since 1500 a total of 338 species of vertebrates had become extinct. In addition, there were a total of 279 species that were in the category of “extinct in the wild” or “possibly extinct.” In other words, a total of 617 species of vertebrates have become extinct, mostly in the last 114 years.
With a quick calculation, the researchers established that this extinction rate is 100 times higher than usual, which is irrefutable proof that we are in a process of mass extinction.
What has caused this decline in biodiversity?
The next question to ask ourselves is: What is causing this sixth extinction? For Eustoquio Molina, Professor of Paleontology at the University of Zaragoza, the answer is easy. The cause of the sixth extinction is due to humans, or rather, human activity. According to Molina, there are three major processes carried out by humans that have favored this decrease in biodiversity:
- The first of these would be the expansive distribution that humans had throughout the planet 100,000 years ago and how hunting killed the large mammals of the Pleistocene.
- Secondly, the development of agriculture 10,000 years ago and how its global expansion notably reduced the biodiversity of many regions, which were deforested for monoculture plantations.
- Third, the industrial revolution, and consequently, global warming, which can finish off a great number of species, including ours.
The paleontologist also points to a series of crucial events that continue to contribute to this sixth extinction such as: the overexploitation of hunting and fishing, the introduction of exotic species, the destruction of natural habitats, as well as the indiscriminate burning of fossil fuels that generates an increase in greenhouse gases. The specialist adds that an increase in these gases will cause sea levels to rise, thus leading to the flooding of coastal regions and islands, as well as a modification in marine currents that can end up releasing methane hydrates and ultimately produce a hyperthermal phenomenon.
Is there room for hope?
Covid-19 has taught us many things, but among them it has faithfully portrayed what a world without human activity would be like. Fauna all over the world reconquered cities, most notably the curious case of the puma that, taking advantage of the curfew, strolled through the Chilean capital this past March 24th.
In spite of this, as Molina himself explains at the end of his lecture, it would be illogical to try to cure a cancer patient by simply telling him to stop smoking. Therefore, it is a common obligation to require governments and institutions to actively participate in stopping and reversing the activities that have brought us to this point. Only with a conscientious and committed citizenry will the change that can stop this sixth mass extinction be possible.
Barnosky, A. D. et al. (2011). Has the Earth’s sixth mass extinction already arrived? Nature, 471(7336), 51-57.
Ceballos, G., Ehrlich, P. R., Barnosky, A. D., García, A., Pringle, R. M., & Palmer, T. M. (2015). Accelerated modern human–induced species losses: Entering the sixth mass extinction. Science Advances, 1(5), e1400253.
IUCN. (2007). Species Extinction – The Facts. Consulted 29 of November of 2020.
Molina, E. (2008). Stages and causes of the sixth mass extinction. Life in the Tertiary. From the Impact of the Meteorite to the Origin of Man, Arcega C. and J. Lahoz (eds). University of Zaragoza, Zaragoza, 187-203.