Because invasive species are among the main drivers of extinction today, conservationists have made efforts to cull mice in favor of albatrosses, rats in favor of puffins, and pythons in favor of bobcats. Illustration by Javier Jaén; Source photographs from Getty

Invasive species have received plenty of attention in our pages in the years since we first shared on this topic. Creative approaches to solving the problem abound. Elizabeth Kolbert reviews two books that take up the moral implications:

Should We Kill Some Wild Creatures to Protect Others?

Where humans have tilted the game in favor of one species, some believe we should cull predators to save their prey. Others think it’s a mistake to pick sides.

The northern spotted owl is about a foot and a half high, with very dark eyes, a greenish beak, and a rim of feathers, called a facial disk, that makes it appear to be regarding the world with worried perplexity. Like most owls, northern spotteds are nocturnal, but, unlike most of their brethren, they are picky. They can live only in old-growth forests in the Pacific Northwest. Their diet is restricted and seems to consist mainly of flying squirrels. They’re incapable of building nests of their own, and so, to raise their young, they rely on tree cavities or on basketlike growths that are produced by arboreal infections and known, evocatively, as witches’ brooms.

The spotted owl’s fastidiousness produced one of the great environmental conflicts of the twentieth century. By the late nineteen-eighties, it was estimated that only fifteen hundred breeding pairs survived. Since the owls depended on old growth, the only way to save them, according to biologists, was to preserve the Northwest’s remaining stands of ancient trees. The timber industry countered that leaving those trees untouched would cost thousands of jobs. The two sides adopted increasingly confrontational tactics. Loggers raced to cut down the most valuable timber before their opponents could secure court injunctions. Protesters blocked forest-access roads and chained themselves to tree trunks. The police brought in heavy machinery to bulldoze their encampments. Environmentalists dressed up as owls and shouted, “No more clear-cuts!” Sawmill workers drove around with bumper stickers that read “I Like Spotted Owls . . . Fried.”

Eventually, the birds—or their non-avian champions—won what came to be known as the “timber wars.” In 1994, the Clinton Administration set aside some 24.5 million acres of forest to protect the owls. But the victory has proved a hollow one: northern spotted owls have continued to decline. A few years ago, a team of scientists analyzed data from eleven study sites in Oregon, California, and Washington State. They found that, since 1995, the number of spotted owls at the sites had fallen by at least fifty per cent. At some sites, it had dropped by more than sixty per cent.

These figures have set off a new conflict, what might be thought of as the “timbre wars.” Researchers believe that what’s now standing in the way of the spotted owl’s recovery is another owl, the barred owl. The barred owl’s haunting call—often rendered as “Who cooks for you? Who cooks for you all?”—is commonly heard in the Eastern United States and Canada. (Spotted owls have a higher-pitched, four-beat call.) The ranges of the two species should not overlap. But, during the past several decades, almost certainly owing to the human transformation of the landscape, barred owls have pushed west. Far less finicky than their spotted kin, they’re also bigger and more territorial. Barred owls compete with spotted owls for prey and nesting sites, sometimes killing them outright.

Last fall, the U.S. Fish and Wildlife Service proposed a plan to try to save the northern spotted owl by eliminating tens of thousands of its competitors. The idea is to lure barred owls into the open by playing digital recordings of their calls. Then “removal specialists” are to pop them, using a “shotgun of 20 gauge or larger bore.”

The slaughter of animals is, of course, routine. Every day, around the world, some nine hundred thousand cows, more than a million goats, and nearly four million pigs are “processed” into meat. Roughly a hundred million lab rats and mice are dispatched each year in the U.S. alone. Countless other rodents are trapped or poisoned because they’re seen as pests.

Compared with this carnage, Fish and Wildlife’s plan might be considered a mere drop in the abattoir. And yet the proposal raises its own set of concerns. As a rule, people don’t interfere with predation. When a lion in the wild takes down a wildebeest, it’s considered fair game. But where can you—or a lion—go these days that’s genuinely wild? If people, either intentionally or accidentally, have tilted the game to favor one species over another, do people then have an obligation to undo the damage? Or does that just compound the problem?…

Read the whole review here.