The Buzz: What Bees Tell Us About Global Climate Change
June 2, 2010 |  by Sharon Tregaskis

There’s not much money in plain old environmental monitoring; but given their profound ecological and economic implications, invasive species—from pythons in the Everglades to the inexorable northward march of the fire ant and the scourge of kudzu encroaching on southern farm fields—have commanded substantial attention from government agencies. Esaias has funded much of his recent work through a grant from NASA for collaboration with USGS and USDA to model the spread of the Africanized honey bee—the “killer” bee—which arrived from Africa in the late 1950s and has since established feral populations in eastern Texas and parts of Florida. Scientists have long expected that as winter temperatures warm due to climate change, the ornery bees will spread north, breeding with their more docile counterparts, disrupting backyard and already compromised commercial beekeeping operations, and attacking humans, livestock, and pets unfortunate enough to get in the way of a swarm.

In the meantime, beekeepers have inadvertently given the invaders a boost. Over the last 100 years, northern beekeepers expanding their apiaries or replacing winter-killed colonies have come to rely on large southern operations for mail-order queens delivered in time to establish a robust colony before the spring nectar flow in the North. After each southern-hatched queen takes nuptial flights from her natal hive—mating with wild drones on the wing to ensure that she will lay the fertilized eggs to Bee1produce a new colony—the queens are shipped north. In each of the last four years, winter die-offs attributed to the stress of travel, pesticides, tracheal and Varroa mites, and colony collapse have amounted to as much as 30 percent of the nation’s colonies, making the queen-rearing trade increasingly vital. Yet, buying mated queens from areas where Africanized honey bees are established has turned into a Russian roulette of hybridized genetics. “At first it’s fine,” says Esaias, who notes that there’s no way to control the mates a queen encounters on her flights. “But then in August when the population gets up, their true African nature comes out.” In the best-case scenario, the apiarist destroys an aggressive colony and starts over the next spring. In the worst-case scenario, the bees swarm and establish feral populations throughout the country. Rumors of the bees’ presence can be enough to torpedo even a well-established queen-rearing business and induce panic among community residents. But until now, scientists have had few tools to guide their search for the bees. And while they’ve known that there’s more to the story than temperature, scientists have struggled to anticipate where feral populations would thrive or collapse.

Esaias found clues in his scale-hive data. Unlike their European counterparts, Africanized honey bees co-evolved with plants and weather patterns that produce twice-yearly nectar flows. In places with a single nectar flow like Maryland, the Africanized bees reproduce, swarm, and then starve waiting for another nectar flow to sustain them. Not so in places like Arizona, southwest Arkansas, and south Florida, where Esaias and his collaborators have demonstrated that nectar flow spikes twice. If the scientists can deduce the parameters that determine nectar flow and map the pattern for the rest of the country, they’ll have a powerful tool to inform both detection and management. “We need to better understand this insect-climate interaction and what it can tell us about our planet,” says Dewey Caron, a professor emeritus of entomology at the University of Delaware. “This is a great test case of a potentially damaging invader we can use to build better models for better predictions.”

In a nascent collaboration with Sam Droege, a USGS Patuxent Wildlife Research Center scientist, Esaias has also begun investigating the relationship of nativepollinators to local plant populations in a study of Osmia lignaria, the orchard Bee2mason bee. “Most of our terrestrial ecosystem has its own set of bees and we don’t even know all of their names and what they eat,” says Esaias. “For something as important as pollination for our terrestrial ecosystems, we need more people working on it—and here I am, just about retirement age.”

In the meantime, says Caroline Esaias, HoneyBeeNet seems to have forestalled her father’s departure from NASA by reigniting his passion for investigation. Caroline was in elementary school when the bees came home with her father and Colin, and although the kids helped, they always knew whose hobby the bees really were. Now 28 and living in the farmhouse where her father was raised, Caroline tends the hive he placed in a back pasture a few years ago. This spring she added three more colonies and put a platform scale, equipped with an electronic monitor like the one her father installed on the Beltsville colony, beneath one of them. In May, she joined HoneyBeeNet herself. Unlike most of her father’s volunteers, committed to a daily check of their hives either at dawn or dusk as the study protocol dictates, Caroline can download data anytime. At Mink Hollow, Wayne Esaias maintains the daily habit that inspired the protocol: “He goes down to the bees in the morning with a cup of coffee, checks the scales, watches the bees,” she says. “There’s always something he’s pondering—it’s part of who he is.”

Freelancer Sharon Tregaskis writes from the Finger Lakes region of New York. This is her first story for Johns Hopkins Magazine.