Ideas

Ideas | Linda Rodriguez McRobbie

Humans make a mess, but invasive species get the blame

Rae Cook for The Boston Globe

A flock of starlings in flight is called a “murmuration,” one of the most pleasing collective nouns. It’s also one of nature’s most pleasing sights, an undulating mass of thousands of black dots that coalesce into hypnotic shapes, like an airborne Rorschach test or a lava lamp.

But to some in the United States, a murmuration of starlings is unwelcome. Loud and aggressive, the species is said to bully the native woodpeckers and bluebirds. Starlings also have a problematic tendency to murmurate near airfields; in 1960, a Lockheed Electra took off from Logan Airport into a flock of some 10,000 starlings and crashed, killing 62 passengers. In 1990, a writer in The New York Times opined that the starling had “distinguished itself as one of the costliest and most noxious birds on our continent.” This, according to the paper, is a pestilent, ravenous bird that defiles with droppings what it doesn’t eat, costing farmers millions.

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The big problem with starlings is that they don’t belong here. They are what‘s called an introduced, alien, or exotic species. If a species is bad enough, like the aggressive starling, we call it “invasive.” In 1992, famed Harvard biologist Edward O. Wilson branded “exotic animals” the second-largest cause of extinctions worldwide, behind habitat destruction. He expressed what was then coalescing into the dominant discourse about introduced organisms: They’re bad news. We don’t want them.

This, in part, is why conservationists were alarmed this past summer when odd species of turtles were spotted in Quincy and Western Massachusetts. It’s why park officials in Des Moines are trying to weed out non-native honeysuckles and Florida conservationists are trying to persuade chefs and supermarkets to serve up lionfish. It’s why the United States and the European Union have been fighting a trade dispute about Maine lobsters in Sweden.

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So what should we do about starlings — and all these other interlopers?

For a growing minority of biologists, conservationists, ecologists, and environmental writers, the answer is simple. Nothing.

The occasion for the Times’ scathing op-ed on the starlings was the 100th anniversary of their introduction into America. On March 6, 1890, Eugene Schieffelin, a wealthy pharmaceuticals maker and inveterate bird importer, released 60 European starlings in Central Park. The starlings loved America. All of it. By 1929, they’d made it as far as Oklahoma. By 1942, they were in California. Now, some 200 million starlings eat, defecate, and bully in almost every state in the Union.

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The Department of Agriculture now considers the bird one of the most worrisome invasive animals, right up there with the nutria gnawing through Louisiana river banks and the Burmese pythons swallowing alligators in the Everglades. “It’s the poster child for what it is we don’t like about invasives,” declares Ron Rohrbaugh of the Cornell Lab of Ornithology. Between 2014 and 2015, more than 1 million starlings in 45 states — notably, just half of a percent of the total US starling population — were killed by the federal government in a bid to curb the bird’s destructive presence.

But starlings may not be as problematic as we think. For one thing, though there is evidence that starlings moving into an area can lead to a local decline of certain native bird populations, there is no evidence that there is a decline in the larger population. In their case against the starling, the USDA notes, “From 1990 to 2013 European starlings were involved in 3,348 aircraft strikes resulting in $6,865,043 in damage costs to the airlines.” Yet during the period of 1990 to 2014, red-tailed hawks — so American they sailed into a John Denver song — cost airlines $23,649,229, the government estimated, and few are arguing to exterminate them.

Supposedly, the birds eat $800 million worth of grain in the United States each year. Yet environmental writer Fred Pearce points out that, if the starling displaces native birds, it’s displacing birds that would have fed on (and defecated on) the same crops. Starlings have done some good things: During the 1934 drought in Illinois, for example, starlings and their ravenous appetite reportedly saw off the destructive chinch bug.

While not exactly defending starlings, Pearce and others worry about what they see as the simplistic dogma of conservation biology: Native is good, foreign is bad. Pearce, an environmental journalist for The Guardian and others, explored the knee-jerk rejection of introduced species in his 2015 book, “The New Wild,” ultimately arguing that successful non-native species, including those labeled invasive, have a lot more to offer than dogma dictates.

Not all alien species are disliked. Both cows and honey bees, for instance, were introduced. The honey bee is now the state insect of 12 states. But during the 20th century, sentiment turned against non-native species, sometimes without regard to their actual impact. In a 2011 paper, Dr. Martin Schlaepfer of SUNY Syracuse and his colleagues determined that “a bias persists against non-native species among scientists.” The positive effects of an introduced species are rarely reported, and scientific literature about non-native species is “frequently scattered with militarized and xenophobic expressions.”

To the US government and the European Parliament, an invasive species is defined as one that might “harm” the ecosystem. But the meaning of “harm” is often based on what humans need or want, not what’s best for nature.

Still, for government, the mandate to oust invaders is clear. “There are a lot of invasive pests where there is really no question, and I would say that a majority of them would fall into that category,” said Dr. Rosalind James, who studies invasive pests of crops in the USDA’s Agricultural Research Service. She points to citrus greening, a disease currently devastating the Florida orange crop. It spreads via the Asian psyllid, a tiny bug that has cut a swath through citrus trees from China to Afghanistan and now the Western Hemisphere. The US government has plunged $380 million into eradicating the disease, and the bug, since 2009.

One of the reasons that the insect and the disease have been so devastating is that the citrus groves are dominated by a single type of orange, said Dr. Matthew Chew, a biologist at Arizona State University. “Any agricultural pest does threaten the food supply,” he said, “but what also threatens the food supply is the choices we have made about agriculture and standardizing it.” Usually, it’s human activity, from pollution to habitat destruction to extermination to increasingly narrow farming practices, that causes the greatest harm to ecosystems and provides a foothold for alien species. The pest takes the blame.

The way we regard alien species is wrapped up in how we view nature and our place in it — or not in it.

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Pearce agrees that there are situations in which an organism, introduced or not, may become a problem for humans. Those situations, he maintains, are not as clear-cut as we’d think. The zebra mussel, for example, is the great villain of invasive species. The New York Times described it in 2014 as a “silent invader” responsible for “vast economic and ecological damage” around the Great Lakes, after its accidental transportation from Central Asia in the ballast of cargo ships in the 1980s.

But that’s not the whole story. The mussel first made it to Lake Erie, which was so polluted in the 1960s and ’70s that it was declared “dead.” The mussels thrived because they encountered little resistance, because so few creatures remained. But as Pearce explains, the Great Lakes owe a debt of gratitude to the hardy mussel: It could not only thrive in Erie’s fetid waters, but also filter pollution and initiate the Herculean task of making the lake livable again.

This surprising pattern emerges in other cases, while the promised alien species apocalypse rarely happens. Ken Thompson, plant biologist at the University of Sheffield and the author of “Where Do Camels Belong? Why Invasive Species Aren’t All Bad,” agrees: “We should be a bit more grateful,” he says, “that given how totally we’ve messed up that there are animals and plants that are still happy to live in these places.”

Pearce worries that seeing off successful non-natives and invasives would sacrifice the one quality that they exhibit so aggressively: the ability to survive. “The problem is that when we root out invasive species, we’re reducing nature’s resilience,” he said. This fits squarely in the mounting evidence that the principle of natural selection works over decades, not just over eons.

The way we regard alien species is wrapped up in how we view nature and our place in it — or not in it. EU legislation targets only those “alien invasive” species that arrived in their new habitat as a consequence of human intervention. “It starts from the very beginning that humans are not part of the natural world,” said Thompson.

The implication is that we have severed ourselves from the natural world to such a degree that we don’t recognize that we are living in an ecosystem and that we’re probably the most invasive species in it. How do we care for something that we must also shape to our own needs?

Which brings us back to our original question: What about the starlings? We could spend time and money trying to exterminate them, more than we already do; certainly, other governments are taking that line. This July, the government of New Zealand announced an ambitious plan to eradicate all of the island nation’s introduced predatory species by 2050, including, but not limited to, cats, rats, possums, and stoats. While conservationists in New Zealand lauded the move, others in the field questioned its ethics and efficacy.

Extermination is costly, can be grisly, and doesn’t always work. It also might just make things worse, damaging ecosystems that have forged new balances. “I’m a big believer in picking fights you’re going to win, and that’s a fight you’re not going to win,” said Thompson. Though he does not concur with Thompson’s perspective on invasives, Rohrbaugh agrees — any management plan needs to take into account the “cascading effects” of removal, “especially if those invasive species have been in place for dozens or hundreds of years, and they have become part of that ecosystem.”

And even then, even after forming a conservation solution based on the best available science, “those management solutions might be entirely impractical and might do more harm to an ecosystem than doing nothing at all,” he said.

Linda Rodriguez McRobbie is an American freelance writer living in London.
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