The Earth has registered in the last 550 million years five great episodes of mass extinction of species, as indicated by Jack Sepkoski and David M. Raup in 1982 and subsequent detailed studies. Currently, the data indicates that our planet is immersed in what could be the sixth mass extinction, also known as the Anthropocene extinction, due to its simultaneous appearance -and in part, causation- to the global impact of human activities.
The current rate of extinction is between 100 and 1,000 times the natural evolutionary average, and the International Union for Conservation of Nature (IUCN) estimates that one in eight species of birds, one in four mammals, and one in every three amphibians are in danger of extinction.
A team of scientists from Queen's University in Belfast (United Kingdom) and the Czech University of Life Sciences in Prague have now published in the journal Biological Reviews the results of a study in which they provide new calculations on the current rates of extinction of fauna species.
The main conclusion of this work is that, indeed, the Earth is in a phase that fully adjusts to what is considered a "great extinction" and that this process can become even more devastating than what is estimated in recent years. studies published to date.
The authors have used population trend data for more than 71,000 animal species, spanning all five groups of vertebrates (mammals, birds, reptiles, amphibians, and fish) and insects, to determine global processes of population declines, increases and stable situation; without counting the species on which there are insufficient data to determine their evolution.
The conclusion of the study indicates that it shows "a widespread global erosion of species, with 48% experiencing declines, while 49% and 3% of species currently remain stable or are increasing, respectively."
The study signed by Catherine Finn, Daniel Pincheira-Donoso and Florencia Grattarola, recalls that "the quantification of this sixth extinction crisis has traditionally been based on the use of the IUCN Red List, with conservation categories assigned to each species evaluated This approach reveals that a quarter of the world's animal species are currently threatened with extinction and ~1% have been declared extinct."
The authors note that an approach that only takes into account the conservation categories analyzed by the IUCN "may underestimate the true extent of extinction processes underway in the wild." In this sense, they point out, other studies such as the Living Planet Report reveal a general trend of sustained demographic declines.
Over the past few decades, it has become clear that global biodiversity has been declining due to human activities, including habitat conversion, the use of pesticides and herbicides and, more recently, climate change, the authors of the new study recall. It is not known how many species go extinct due to such activities, but scientists have been trying to track down the species most at risk of extinction.
Those responsible for the new review insist that the IUCN lists of endangered species only show which species are currently at risk of disappearing; they do not look at details such as the drop in population levels of species that are not currently at risk of extinction.
The method of analysis of the group headed by Catalina Finn concludes that 33% of the species currently classified as non-threatened on the IUCN Red List are actually in a spiral towards extinction.
The researchers also found that, as a group, amphibians are experiencing the largest declines in population. The study also shows significant declines for birds, mammals, and insects; and to a lesser extent for reptiles and fish.
By geoclimatic zone, the new study indicates that the declines are observed to be more pronounced in the tropics, noting that species in those areas tend to be more sensitive to change.
The conclusion is that "global biodiversity is entering a mass extinction, with the heterogeneity and functioning of ecosystems, the persistence of biodiversity and human well-being under increasing threat."