Researchers at the University of Queensland looked at something called the anthropogenic Allee effect (AAE), a theory that proposes a critical population level threshold below which the likelihood of a species going extinct increases substantially due to rising prices for rare animals incentivizing more hunting.

Using mathematical models to determine how quickly wildlife populations can decrease as prices for animal products rise in response to animal scarcity, the researchers found that the population thresholds proposed by AAE theory can drastically underestimate extinction risks.

While these findings would appear to call into question the biological sustainability of trophy hunting, the debate over trophy hunting is typically centered on social and economic outcomes.

The U.S. Fish and Wildlife Service’s announcement in November that it was lifting a ban on the import of elephant trophies from Zimbabwe and Zambia — an order President Donald Trump said in a tweet two days later that he had put on hold — was merely the latest flashpoint in a debate that has been raging for years.

Proponents of trophy hunting insist that it generates revenue that can be directed towards conservation efforts and creates incentives for local populations to conserve particular species. Opponents counter that there is no research proving these claims to be true and that there are better alternatives, such as eco-tourism, the benefits of which are more established and do not rely on killing animals for sport.

According to the Matthew Holden, an applied mathematician at University of Queensland in Australia whose work focuses on how human behavior reacts to and impacts conservation policies, we don’t know enough about how trophy hunting affects wildlife populations to say with any certainty whether or not the legalization of the transport of elephant trophies could drive African elephants to extinction.

“Both sides of the trophy hunting debate make seemingly logical arguments, but actually very little is known about the social and economic side of trophy hunting and that’s a big concern,” Holden said in a statement.

Holden is the lead author of a study recently published in the Journal of Theoretical Biology that adds a significant new dimension to the debate, however. He and a colleague at the University of Queensland looked at something called the anthropogenic Allee effect (AAE), a theory that says species extinctions can be driven by the increasingly high prices people are willing to pay for wildlife and wildlife products as target species become more rare due to hunting and other pressures.

“Our research isn’t specific to elephants and trophy hunting,” Holden said, “but the existence of price rarity relationships have been shown time and time again in fish, mammals and even butterflies. These relationships can be detrimental to animal populations.”

AAE theory holds that there is a critical population level threshold below which the likelihood of a species going extinct increases substantially. “Past theory says that if the price for animal products — like elephant trophy hunting expeditions — were to skyrocket as animals declined, this would create extra financial incentive to sell these products,” Holden said. “The theory says that more animals then die from increased hunting, which would then skyrocket product price further, in a vicious cycle towards extinction.”

Using mathematical models to determine how quickly wildlife populations can decrease as prices for animal products rise due to animal scarcity, Holden and team found that the population thresholds proposed by AAE theory can drastically underestimate extinction risks.

“Our analysis shows that this threshold can be much higher than the original theory suggests, depending on initial harvest effort. More alarmingly, even species with population sizes above this Allee threshold, for which AAE predicts persistence, can be destined to extinction,” Holden and co-author write in the study. “Introducing even a minimum price for harvested individuals, close to zero, can cause large populations to cross the classic anthropogenic Allee threshold on a trajectory towards extinction. These results suggest that traditional AAE theory may give a false sense of security when managing large harvested populations.”

While these findings would appear to call into question the biological sustainability of trophy hunting coupled with unrestricted trade and transport of animals and animal parts, the debate is typically centered on social and economic outcomes. For instance, a 2015 report by US-based NGO Safari Club International, one of the largest trophy hunting advocacy organizations in the world, claimed that trophy hunting contributes as much as $426 million every year to the economies of eight African countries — Botswana, Ethiopia, Mozambique, Namibia, South Africa, Tanzania, Zambia, and Zimbabwe — while creating more than 53,400 jobs.

But a subsequent report released earlier this year by the Humane Society International, the international arm of the Washington, D.C.-based Humane Society of the United States, examined those claims and found that SCI had “grossly overstated the contribution of big game hunting” to those eight countries’ economies, and that, in reality, tourism in Africa “dwarfs” trophy hunting as a source of revenue.

If even large animal populations that are considered safe from extinction can be threatened by trophy hunting, however, that must certainly be taken into account by decisionmakers like those at the U.S. Fish and Wildlife Service who are weighing whether or not to allow sport hunters to bring their trophies home — which would only incentivize more hunting and could possibly trigger the “vicious cycle towards extinction” identified by Holden.

“Our study shows this process can start when the population is much larger than previously thought,” Holden said. “It suggests large populations predicted safe by previous theory may in fact be in danger. African elephants may fit this category — they are abundant.”

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