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venerdì 21 agosto 2015
Human ‘super predators’ driving extinction rates
The rate at which human ‘super predators’ kill adult prey could “rapidly drive prey declines, degrade ecosystems and impose evolutionary change”, according to a new study published this week in Science.
While non-human carnivores target younger animals, humans almost exclusively target adults, driven in many cases by competition and a desire for large trophies.
Furthermore, where non-human predators target young prey – young prey being easier to pick off and less likely to put up a life-threatening fight – humans feel free to go for the adults, as “advanced killing technology” ensures that we do not face the same risks as other predators.
This targeting of adult prey has a profound effect on species’ recovery, according to the study, with their removal from the ecosystem severely hampering the reproductive potential required to buoy populations.
The study further suggests that hunting adult prey can, in some senses, become a vicious cycle, stating: “Low prey abundance can drive aggressive exploitation, because of the increased economic value of rare resources”.
Speaking to sciencemag.org, Gerardo Ceballos, an ecologist at the National Autonomous University of Mexico, said: “Any predator capable of exerting such impact will eventually drive its prey to extinction.”
And what an impact that is.
The study’s original focus was on fish, inspired by one of the authors noting a disparity between the ways marine predators and humans impact fish populations. The study states that humans fish at a rate 14.1 times the take of marine predators.
Also highlighted, however, is the fact that, while humans and other predators prey on herbivores at similar rates, we hunt carnivores at a rate 9.2 times higher than non-humans.
The study further suggests that the rapid development of the technological advancements we use to hunt prey has not allowed prey populations to adapt in a way that would enable them to successfully avoid us, which, in itself, is contributing to falling prey numbers.
The study’s authors called for dramatic alterations to the way we as super predators hunt, saying it is time we sat up and took notice of the profound effect we’re having on the Earth’s animal population.
“The implications that can result [from hunting adult prey at exceptionally high rates] are now increasingly costly to humanity, and add new urgency to reconsidering the concept of sustainable exploitation.
“Transformation requires imposing limits of humanity’s own design: cultural, economic and institutional changes as pronounced and widespread as those that provided the advantages humans developed over prey and competitors.”