Planet of the Pigeons

A guest rant by Joe Eaton

Nathanael Johnson’s “Unseen City: The Majesty of Pigeons, the Discreet Charm of Snails & Other Wonders of the Urban Wilderness” (Rodale 2016) is the kind of book I wish I could like. Johnson, who lives in Berkeley (as I do; we’ve never crossed paths), builds a narrative around his attempts to interest his young daughter in the natural world, or at least its urban representatives. With the exception of the American crow, most of his subjects are non-native species: rock pigeons, European garden snails, eastern fox squirrels. That’s OK; you watch what you got. He’s a competent writer and seems to have done a fair amount of research. But he stumbles badly at a couple of points, in particular in putting a Panglossian spin on exotic-dominated ecosystems and dismissing widely accepted ideas about biodiversity.

A tangential error involves the historic status of the American crow on the Pacific Coast. Johnson quotes corvid expert John Marzluff of the University of Washington: ” The American crow isn’t endemic to the West Coast, it followed suburban developments across the United States, glorying in the irrigated lawns that turned the inhospitable West into ideal habitat. They reached the West Coast sometime around 1960, Marzluff said.”

That’s’ demonstrably wrong, and I find it hard to believe that Marzluff, who knows crows, actually said that—unless he was talking about the Seattle area. It’s certainly not true of northern California. In their “Directory to the Bird-Life of the San Francisco Bay Region” (1927), Joseph Grinnell, founding director of UC Berkeley’s Museum of Vertebrate Zoology, and his colleague Margaret Wythe wrote that the “Western American Crow” was common “north of the Bay, especially in those portions of Marin County immediately adjacent to salt water,” with additional records from all over the Bay Area. Grinnell and Wythe also mention that crows nested on the UC campus as early as 1872. Later, in “The Distribution of the Birds of California” (1944), Grinnell and co-author Alden Miller give the crow’s range as “southwestern coastal slope southeast to Mexican boundary” and “northern coast belt, north from Monterey County to Oregon line,” noting its predilection for tide-flats and sea-beaches.

A small thing in itself, although it suggests a certain lack of rigor in fact-checking. But there’s worse.

The big one, the unforgivably stupid one, comes in a chapter about Argentine ants—a species native to South America that has colonized California and other Mediterranean climate zones, displacing indigenous ant species and disrupting ecosystem processes like seed dispersal; horned lizards, which feed mostly on ants, find Argentines less appetizing and/or nutritious than the natives. Johnson tries to make the case that the Argentines are really not that bad. “ Immigrant species often do reduce native populations, sometimes significantly ,” he concedes. “But the ecologist Mark Davis has pointed out that they seldom cause extinctions, and when they do it’s of populations in isolated habitats like lakes or islands. All this mixing may yield more bidodiversity by producing more combinations, hybridization, and new species.” (I don’t know Davis, but it doesn’t surprise me that you could turn up an alleged ecologist who likes invasive species. You can still find climate scientists who don’t accept human responsibility for global climate change. You can probably still find medical types who believe smoking is good for you. I suspect Davis is that kind of contrarian outlier.)

Just lakes or islands, though ? Well, that’s all right, then. Does Johnson—or Davis for that matter—know how much of the planet’s biodiversity it owes to lakes and islands, the places where we can catch evolution in the act? Let’s just write off Darwin’s Galapagos and Wallace’s Malay Archipelago, along with Hawai’i and the rest of the South Pacific’s islands, Madagascar, New Zealand, Cuba, Socotra, Taiwan, the Canaries, the California Channel Islands. Let’s write off the great lakes of the East African Rift, with their famous species flocks of fish, and Baikal, and Titicaca, and Mexico’s Cuatro Cienegas, and the springs of the Edwards Plateau and Death Valley. Forget all the “islands on the land,” the tepuis of the Guiana Shield, the Sky Islands of the Southwest, the caves and sinkholes and lava tubes with their unique animals, the patches of serpentinite soil with their endemic plants. Just lakes and islands, or equivalents. They don’t count.

But there’s more. “ Disturbance and mixing spur evolution, and scientists are finding many new species and hybrids arising with migration,” Johnson continues. “On balance, it seems, the result of ecological immigration isn’t gray uniformity, but just the opposite: Naturalizing species have given us richer biodiversity. “

This is pernicious claptrap. Biodiversity is not a numbers game. Biodiversity is a matter of relationships—plant-pollinator, prey-predator, all the mutualisms and commensalities and symbioses—that came together over millions of years, and can be destroyed in the blink of an eye.

Let’s talk about Hawai’i. Let’s narrow it to the birds of Hawai’i, forgetting for the moment the silversword plants and lobelias, the tree snails and picture-winged flies. The landbirds of Hawai’i were the winners of a series of natural lotteries, migrants that veered off course and made landfall on newly-minted islands after the lava had cooled. This happened maybe a couple dozen times over a span of 5 million years: maybe a flock of geese, a pair of thrushes, a pair of finches. With a multitude of environmental niches up for grabs, the descendants of these founders morphed into something completely new, something unique in the world. The waterfowl became huge flightless grazers with beaks like the jaws of a tortoise. The finches evolved a whole panoply of bill shapes, for crushing seeds, sipping nectar from the curved corollas of flowers, tweezing insects from wood and bark. The hawks and owls developed new wing configurations to navigate the forests where their songbird prey lived.

Most of that diversity is gone. It happened in stages. The first Polynesian settlers ate the flightless ducks and geese (to be fair, they couldn’t have known there weren’t more waiting on the next island, had there been a next island), cleared the low-country forests for taro fields, and probably made a serious dent in the songbird population by collecting feathers for royal regalia. Their pigs and dogs, and the rats that stowed away in their voyaging canoes, did their own damage. But many bird species persisted, especially in the unpopulated high country.

Then came the Europeans, with their livestock and other dependents and their more powerful and efficient tools for deforestation. Hawai’i had no mosquitoes before European ships arrived in the late 18th century. Introduced accidentally, they vector diseases that wiped out most of the native songbirds. Mongooses imported to control rats in the sugar cane fields did in more birds than rats. Exotic plants outcompeted the native species that the birds relied on for food and shelter. The cumulative impact was devastating. A number of Hawai’ian birds have gone extinct in my lifetime, and they won’t be the last.

There are still birds in Hawai’i, of course. Some are the descendants of escaped cage birds. Others were deliberately released by a group called the Hui Manu (“Bird Society”), the territorial government, or private individuals, for various reasons. The islands today are full of Brazilian cardinals, Java sparrows, African canaries, North American mockingbirds, saffron finches from the West Indies, Indian mynahs, Japanese white-eyes and bush-warblers. It’s like a big walk-through aviary. This isn’t “richer biodiversity.” These birds don’t fill the roles of the extirpated natives; they don’t pollinate the native plants, and most of the native bird-eating raptors are among the extinct. Some exotics, in fact, are reservoirs for the pathogens that killed the endemic birds. Give the mynahs and cardinals a few million years and they might turn into something interesting. For now, they have as much in common with the original bird community as a random collection of strangers at a karaoke bar has with the San Francisco Symphony.

We have a long and unfortunate record of trying to improve nature by bringing in non-native plants and animals. There was Eugene Scheiffelin, the idiot who wanted to see all the bird species mentioned in Shakespeare established in the United States, which is how we got the pestiferous European starling. Sportsmen introduced rainbow trout to the previously fish-free lakes of the Sierra and European wild boars to any number of places. Nostalgic New Zealand settlers sent home for the birds and beasts of England, ferrets and stoats among others; the country is now engaged in a costly campaign to eradicate them. In Stalinist Russia, a crackpot biologist named Isaak Prezent promoted the acclimatization of exotic wildlife to fill allegedly vacant niches and further enrich Soviet biodiversity by hybridizing with the natives, or each other. That worked about as well as Lysenko’s approach to crop-breeding. But Johnson doesn’t seem to hear the echoes.

I can almost understand Johnson flinching from the fact that his daughter will grow up in a diminished, depauperate world. She will, though, pigeons and Argentine ants notwithstanding. Denial doesn’t do her—or her generation—any favors.

Leave a Reply