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By Miguel Angel Criado
Neither the white shark nor the lion. The only super predator on the planet is humans. Now that subsistence hunting and fishing are residual, a study shows that humans have predation rates up to 10 times higher than those of large carnivores. The work, which quantifies the human predatory character, is committed to a radical change in hunting and fishing practices. For the first, it requires learning to live with animals. For the second, stop fishing the adult fish and go for the smaller ones.
That humans are the greatest predator on the planet is said by the long list of animal extinctions at the hands of man. From mammoths and saber-toothed tigers to the giant armadillo, passing through the near annihilation of the American bison or the practical disappearance of at least two species of rhinoceros, in almost all cases humans were and are the causal agents. On some occasions, extinction follows the serious deterioration of the ecosystem where the animal lived, on others it is human advance itself that takes an entire species away. But today, it is human hunting and fishing practices that compromise the future of animals.
A group of Canadian ecologists has wanted to unravel what makes humans so lethal and quantify their degree of predation compared to the largest predators on the planet, such as big cats, marine mammals or sharks. To do this, they reviewed all the scientific literature they found with official studies and statistics on human hunting and fishing or research with data on their rivals at the ecological peak. In his work, published in Science, included almost 400 species of predators, 282 marine and 117 terrestrial.
"We examined all the available data on marine animals and terrestrial mammals from every ocean and every continent except Antarctica. Most of the information is from 1990 onwards," said Hakai-Raincoast Professor of the Chair in a teleconference. University of Victoria (Canada), Chris Darimont. According to their estimates, human marine fishing is the dominant predator of adult prey, with a median exploitation ratio (middle or central value) of 14% of the total biomass of adult specimens per year. This median does not reflect the extreme values, with cases of species reaching 80%. "This median ratio is about 14 times that of any other non-human predator in the ocean," Darimont adds. Be it killer whales, sharks or tuna.
Humans are the only predator that turns other predators into prey
On land, the data, although minor, is just as revealing. Humans and other predators show a similar rate of predation: the former capture up to 6% of herbivores such as deer, caribou or elk, while the latter lower the percentage to 5% annually. However, humans are the only predator that turns other predators into prey. Combining these two facts, the human being has a rate of predation of terrestrial animals nine times greater than that of the lion or the tiger. And that the researchers removed from the equation the wolf, which accounts for a third of all predators hunted by man.
"In general, we do not eat large carnivores, so they are killed as a trophy, for reasons of competition, to reduce losses in livestock, or for the medicine"(sic), Darimont comments in an email. Tens of thousands of years ago, humans, in a slow process, began to stop being prey of these animals to become predators. The different technologies for hunting, from the bow even the rifle through the use of the dog, and in the last century, the use of fossil fuels, has meant that hunting has little cost for humans when for other predators there is always the risk of getting badly injured.
This combination of human behavior and technologies is, for researchers, the basis of the mismatch of many ecosystems. The other predators choose younger and weaker specimens as prey. The short-term consequence is that they do not reduce the reproductive rate of adults and eliminate possible foci of infection among herds. In the long term, as a mechanism of natural selection, they favor the genetic improvement of their prey. Humans, on the other hand, choose the best pieces, adults in their best splendor, chosen for having the best antlers or the largest mane. The short ecological impact is evident, the consequences of this long artificial selection have yet to be studied.
Pezqueñines, yes thanks
The same analysis was applied to marine species. The result is problematic because hunting, which is mostly for the trophy or the misnamed traditional medina, is not the same as modern and industrial fishing, which is fed by millions of people. It is also paradoxical, since it implies contradicting the current paradigm of marine conservation exemplified in the official campaigns of the minnows, no thanks.
The central paradigm of fishery resource management needs to be reconsidered "
Chris T. Darimont. Victoria University
"Evolutionary change among human prey driven by targeting adults has reduced body size, especially among fish. This is concerning because smaller fish have fewer offspring and populations no longer support human catches as in the past, "says Darimont.
Does that mean that the whole model of sustainability of fisheries based on the capture of adults is not so sustainable? "Yes, indeed, we are suggesting that the core paradigm of wildlife and fishery resource management needs to be reconsidered and needs to be reconsidered because, especially in the marine environment, when we look at the reproductive strategies shaped by evolution These are supported by a predatory regime that focuses on juveniles and maintains low levels of exploitation among adults, which benefits these populations and, ultimately, humans, "says the Canadian researcher.
Researchers believe that a return to balance would require action on several fronts. As for land animals, only a change in human behavior could save the big predators. "In some cases, protecting large carnivores threatened by trophy hunting will require social pressure to drive political change. The moral rejection expressed around the world for the death of Cecil the lion tells us that time may be a little closer, "says Darimont.
Regarding fishing, his colleague and study co-author, Thomas Reimchen. points out that it is not so much a matter of stopping the adults from fishing to entangle the young, but of adjusting the ratio of human predation to the natural one. "It is about going to rates of extraction of juveniles similar to that of other predators that, in general, are less than 10%", Reimchen points out. That would drastically reduce fish catches. In addition, both the capture and the processing of the small specimens is more expensive than the large ones.
The researchers recognize that it is a challenge of such magnitude that it presents great difficulties but, they add: "It is not very different from what is being talked about with increasing frequency and intensity of changing our model based on the carbon economy." It is the super-predator character, both in the use of fossil fuels and in that of biodiversity, that has brought humans and the planet to the current situation.