Feral pigs and donkeys may be more salvation than scourge for ecosystems, study finds

Unscientific bias against “wild” or “invasive” animals threatens to undermine one of the major stabilizing trends that make ecosystems healthier, a new paper argues.

Introduced species such as feral pigs, horses, donkeys and camels are a powerful force for “rewilding” (the reintroduction of wild animals into ecosystems where humans have exterminated them), according to one report. There is. The study was published Thursday In science.

In many such ecosystems, large herbivores spread seeds, increase plant diversity, and act as “ecosystem engineers”—and that’s because they are “introduced” species. This is true, the authors argue, whether deaf or “conventional.”

“One way to talk about this is whether a visitor from space who doesn’t know the history could tell which megafauna are native or invasive based solely on their impact. “That’s true,” said Eric Lundgren, a biology doctoral student at the University of Arizona. State University.

A megafauna is an animal that weighs more than 44 kilograms (approximately 100 pounds). This is the key element. This is because much of the data regarding the malignancy of “invasive organisms” in general is based on studies conducted on small animals, plants, and pathogens.

But in the case of large animals, if foreign visitors can’t tell the difference, “nativeness ends up not really helping us understand how the ecosystem works.” says Lundgren.

The study refutes widely held beliefs about whether invasive species are harmful, or what Lundgren described as a quasi-religious perception that some species inherently belong to a given landscape and others do not. are doing.

This belief has been the driving force behind a wave of costly and often futile campaigns since the 1990s to eradicate species such as: texas wild hogwild horses throughout the western United States and donkey and camel In Australia.

In these culling campaigns, land managers are killing millions of “wild” megafauna and are debating even more drastic interventions. In Texas, for example, state officials suggested: Planting a poison called warfarin into the landscape To kill wild pigs. Ranchers argued that the poison could enter the food chain and kill carrion eaters and, in some cases, humans who ate contaminated meat.

Scientific research has argued that much of this killing is unnecessary or even harmful to the ecosystems it is meant to protect. Introduced species have “partially offset” a long series of extinctions and overall declines in large herbivorous mammal populations since prehistoric times, the authors write.

The researchers note that these animals are “thought to have a disproportionately negative impact on plants compared to native megafauna,” but that 200 studies on the impacts of non-native large herbivores have been conducted. After examining these studies, they found that “there is no difference between the impacts of introduced and native megaherbivores.”

Instead, it turns out that the most important determinants of a species’ impact on its surrounding ecosystem are its size and dietary preferences, rather than where it comes from.

For example, large herbivores like horses and camels tended to reduce grass diversity, whether they were in their native habitat or in new ecosystems abroad.

Native pigs living in the forests of Eurasia do the same thing as wild pigs in America and Polynesia. They uproot plants, eat crops, and poop on the landscape, creating large muddy crawlies. in an attempt to cool myself down — without any consideration of the farmer’s desire to run a decent and profitable farming operation in the same space.

However, from another perspective, these actions can be seen as beneficial to the environment. And if those animals are native species, often depicted as such. For example, by disturbing existing vegetation, pigs also create space for new plants to grow. Their droppings can cause algae blooms in waterways because it is rich in nutrients. This means that they are a particularly important source of natural fertilizer for the seeds that pigs spread as well.

And their yago are essentially small ponds that help trap and hold water in dry landscapes. Ecologists think it’s useful For example when done by bison. (On the other hand, the African buffalo that were introduced to Australia left Yabara. linked To reduce the incidence of destructive wildfires. )

By doing all of these things, pigs are drawing attention to a long-extinct species that bears some resemblance to the giants that took root and snorted their way through the forests of North America during the last ice age more than 10,000 years ago. Lundgren argued that they may serve a similar function to peccaries.

And often the impact of native animals on native plants (such as the western bison disrupting the recovery of Yellowstone’s aspen trees) is explained as follows: ecosystem engineering.

Let’s use elephants as an example. Native to Africa and Asia (formerly North America), they often come into conflict with local farmers because they have very different needs than the landscape. Its needs, in the eyes of agronomists, are as destructive as those of any other wild animal. pig. Elephants knock things over, strip and kill trees, and eat and trample fruits and vegetables.

On the other hand, they Possibly useful feature in forests — but still, some botanists argue, Elephants have a negative impact on native trees and shrubsand in some African national parks, land managers insist on killing them To save those seeds.

But Lundgren argued that no matter how destructive existing species like bison and elephants are, they have one significant advantage over new species. When biologists advocate their removal, everyone understands that what they are proposing is “a clear priority.”

“Invasion biologists, on the other hand, argue that: [what they’re expressing] It’s not a preference, it’s somehow forced by the world. The world has taught them that those preferences are real. ”

Scientists have long distinguished between native and new species. The term “neoplastic” refers to “new plants” that exist in a particular landscape.

But as the number of invasive species has increased, the tenor of that debate has changed.This is a “global effect of an increasingly connected world and growing human population size,” says invasion biologist Petr Pišek. wrote on An overview of 2020 that reveals many evils.

“Invasive alien species disrupt biogeographic areas, impact the richness and richness of native species, and increase the risk of extinction of native species,” he wrote.

This discussion sometimes gets ugly.

Opponents of “invasion biology” draw a sordid connection to early 20th century concerns about alien species, such as the Nazi campaign to replace animals introduced in the Third Reich. is paying attention to. Contains appropriate German ethnicity.

However, “most judgments about the aesthetics of introduced species, however, [racist] motivation,” said leading ecologist David Simberloff. wrote on A 2003 article in Biological Invasions.

But unlike Nazi claims about harm from non-German species, modern-day “harm is easily recorded,” Simberloff added.

In contrast, ecologist Mark Davis Discussed in Nature When scientists decide which species to grow and which to cull, it is precisely the harm, not the cause, that they must evaluate.

Characterizing invasive species as “promoting the extinction of beloved ‘native’ species” contributes to pervasive prejudice against invasive species, and is a threat to the general public, conservationists, land managers, and policy makers around the world. It has also been accepted by many scientists. ”

That’s unfortunate, he argued, because “the practical value of the native versus exotic dichotomy in conservation is diminishing, and even becoming counterproductive. Conservationists still consider this distinction to be a central guiding principle.”

Or as Brown University ecologist Dub Sachs. told the New York Times: “I think the dominant paradigm in this field is still the ‘if in doubt, kill me’ attitude.”

Each of these killings and exclusions has unintended consequences. Since the 1930s, land managers in Nevada’s Death Valley have removed burros, sometimes shooting them.According to the National Park Conservation Association, Barros put an excessive burden on the ecosystem This is because they eat so many plants that they “hog the water.”

Other evidence suggests that donkeys actually increase water supply by digging a well A 2007 study of donkey removal in the western United States and Australia found that eradication of donkeys inadvertently caused destruction It was originally a wetland that should be protected.

“They eradicated [the donkeys]The wetlands were then filled with cattails and reeds, becoming dry and anaerobic. And all of these endangered native fish and wetlands are gone,” Lundgren said.

“So now land managers are manually mowing the vegetation. And yet they’re still trying to eradicate these animals from all these areas.”

This vision of war between indigenous peoples and invaders stands in sharp contrast to the vision often adopted by indigenous peoples in both countries who have seen their ecosystems transformed over the past few centuries, he noted. do.

For example, anthropologists working among the Anishinaabe people of the upper Midwest recorded that many of their respondents viewed the colonization of their lands by new plant “nations” as: There is. “It’s a natural form of migration.”

And ethnographers in the Australian outback, where perhaps half a million donkeys were killed, found that the Aboriginal people they interviewed believed in “animal values.” lies in the ability to live and thrive in the environment rather than claiming to be an original component of the fauna. ”

Within those communities, he added, “it’s generally thought that… [nonnatives] Everyone now has the right to live in this country. ”

Lundgren argued that these examples suggest how complex and controversial the question of what belongs is.Most Americans want wild horses and donkeys stay on public landand many Native Hawaiians deeply attached to to wild pigs, descendants of domestic pigs introduced by our ancestors.

“Based on Earth’s history, we can make the argument that if we introduced elephants into western North America, it would actually be very appropriate for our ecosystem, given that such animals have always existed. You can,” he said.

(At least until about 13,000 years ago.)

Lundgren argued that decisions about what to do with these animals are political or philosophical rather than scientific, and he believes scientists need to respond.

“If you’re going to make decisions to do things, you have to be transparent about what those values ​​are.”