2024-01-31 19:07:32
Vertebrate species that have gone extinct in the last 100 years should actually have gone extinct over 10,000 years. It is one of the conclusions reached by Mexican ecologists Gerardo Ceballos and Rodolfo Dirzo, specialists in the study of the rampant disappearance of animals and plants in some of the most biodiverse habitats on Earth. Their research has earned them recognition with the Frontiers of Knowledge Award in the Ecology and Conservation Biology category. This is the 16th edition of these awards given by the BBVA Foundation.
Gerardo Ceballos, from the National Autonomous University of Mexico, clarifies that “evolution works as a process of extinctions and generation of species; in normal times there are more species that originate than those that disappear and diversity increases.” The difference today is the speed with which these disappearances are occurring. The work of the two winners “has shown that current extinction rates for many organisms are much higher than those occurred over the preceding two million years,” according to the jury’s ruling.
Human-caused extinction
Ceballos himself concluded, in research published in 2015 in “Science Advances”, that vertebrate extinction rates today are between a hundred and a thousand times higher than those that have prevailed in the last million years. That is why we are already talking about the Sixth Great Extinction of species. The last one occurred in the Tertiary Cretaceous, 65 million years ago, when the dinosaurs disappeared from Earth.
Previous extinctions were very catastrophic, wiping out more than 70 percent of the planet’s species. They were caused by natural disasters, such as the fall of a meteorite. The fundamental difference with the current one that ecologists talk about is that, in this case, it is caused by human actions. That is why some describe it as the extinction of the Anthropocene. The meteorite would now be ourselves.
“Defaunation” and pandemics
Fellow award-winner Rodolfo Dirzo, from Stanford University, coined the term “defaunation” to refer to the uncompensated absence of animals. It would be the equivalent for fauna of the concept “deforestation” for flora. Dirzo believes that, in addition to worrying about the disappearance of species, we should also be worried about the extinction of populations of a species. It is of no use for elephants to survive in some areas of Africa if they disappear from other areas, because in those areas the vegetation that served as food for these animals would grow unbalanced and that will cause alterations in the ecology of that area. It is of no use, they add, for jaguars to survive in Brazil, if they disappear from Central America.
Because, furthermore, if large animals disappear from an area, these species become “losers”, and smaller animals, such as rodents, will benefit from this absence and will be the “winners”, explains Dirzo. But these smaller animals carry pathogens, such as viruses and bacteria. As these small animal populations increase, the chances of transmitting diseases to humans increase. “They can put us at risk of facing a next pandemic, given the proliferation of these diseases and the current mobility of human beings,” adds the ecologist. In this way, there are facts that may seem unrelated to each other, but this is not the case: a massive hunt for elephants, for example, could pose a risk of a new pandemic for humans.
Impacts on the human population
But we said before that the cause of this Sixth Great Extinction is human action. This is specified, according to Dirzo, in the five “human” factors that contribute to “defaunation”: the change in land use to convert it into pasture or urbanize it; the overexploitation of resources; pollution, which includes everything from chemicals to plastics in the oceans and a countless spectrum of polluting actions; the introduction of non-native, or invasive, species into ecosystems to which they do not belong; and climate change. All these factors act in an intertwined manner “and this makes the problem of addressing biological extinction much more complex,” concludes Rodolfo Dirzo.
Gerardo Ceballos (born in Toluca, Mexico, in 1958) and Rodolfo Dirzo (Cuernavaca, Mexico, 1951) graduated in Biology from the Autonomous University of Mexico. Separately, but in a complementary way, they have investigated the extinction of species, the interaction between plants and animals and the consequences of that extinction. And they have contributed, according to the jury of the BBVA Foundation’s Frontiers of Knowledge Awards, to providing “the necessary scientific basis” to justify the adoption of conservation measures “based on evidence” that reveals, for example, the “serious impacts of that extinction on the human population”.
The BBVA Frontiers of Knowledge Awards are endowed with 400,000 euros in each of its eight categories. Their objective is to promote scientific research and cultural creation in science, technology, humanities and music. They have been awarded annually since 2008.
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