In this space last September, I broached the culturally charged subject of eating insects. Eating them on purpose. Insects are plentiful, a great source of protein, easy to raise and much more environmentally friendly than the more familiar (to Westerners, anyway) vertebrates widely available at your deli counter: cows, chickens and pigs. Let's turn that plague into a plate of locusts.
I come not to bury bugs but to praise them further. Because arthropods can be good on both sides of the food equation: a study by North Carolina State University researchers working in New York City quantified the food waste disposal ecosystem service provided by our hungry six-legged compatriots. And the finding is not a throwaway with regard to what we throw away. The results, published online in early December in the journal Global Change Biology, revealed that insects—and other six-legged critters that perhaps only an entomologist would recognize as being noninsects—in a single 400-square-meter street median could be consuming annually as much as 6.5 kilograms of tossed, dropped and, if there's a bar close by, regurgitated food. (One reason the neon lights are bright on Broadway is so you have enough visual input to tiptoe your way past the piles of semidigested pizza and chicken wings near drinking establishments late on a Friday or Saturday night.) And that's assuming the insects take the winters off, which would really mess up Aesop's ants versus grasshopper auditing results.
To do their investigation, the genteel Southern scientists visited my hometown and proceeded to dump garbage in dozens of sites, within parks and in the aforementioned street medians. Their test materials, “expected to attract fat-, sugar-, and protein-feeding animals,” were Ruffles Original potato chips, Nabisco Nilla Wafers and Oscar Mayer hot dogs. (Oh, I wish I was an Oscar Mayer weiner, part of this here urban garbage caper, 'cause if I was some junk food in this study, I'd get published in a scientific paper.)
Six and a half kilograms of food per street median may not sound like all that much, so the researchers extended the area to illustrate the cumulative effect: “We estimated that arthropods in the medians of Manhattan's Broadway and West St. could remove 600–975 kg (dry weight) of food waste per year—equivalent to approximately 60,000 hot dogs, 200,000 Nilla Wafers, or 600,000 Ruffles potato chips.” We humans make a lot of garbage, relegating the insect waste removal total to what the scientists called “modest but notable. Without these animals, more littered food waste would accumulate in cities.” Which means that insects are eating food that otherwise would be attracting and nourishing rats. A heartfelt thank-you, insects.
One reason the North Carolinians tested both park sites and street medians was their expectation that the wider array of insect species in parks would be a more efficient trash-digesting community. “Theory and data from natural systems suggest that the magnitude and resilience of this service should increase with biological diversity,” they wrote. So they were surprised to find that insects in the less diverse street-median environment actually consumed up to 3.3 times more of the snacks.
Perhaps upper crusty park insects have a more discerning palate, and the study's selections couldn't compete with the plethora of culinary delights available in our emerald spaces. Items such as buried squirrel nuts, street vendor meat and New York's special blend of dog feces surely make our parks a hexapod paradise.
And yet a single organism may account for the medians' superiority at making food disappear—and it's not that quintessential urban insect, the cockroach. Because roaches, like your between-jobs brother-in-law, prefer an extended stay inside your home, not out on the mean streets. No, the key critter for street-median food removal is what is commonly known as the pavement ant.
Of said ant, the study authors explained that, much like my own immigrant ancestors, “this Palearctic species was introduced to North America more than 100 years ago, is common in urban areas, and—consistent with its occurrence in medians—prefers to nest near pavement.” Seems that when Emma Lazarus wrote, “Give me your tired, your poor, your huddled masses,” she inadvertently invited the ants to the party: their colonies average about 10,000 workers. That's enough ants to make an exterminator cry uncle.