Stinging Wasps Moving North Due to Warming?
for National Geographic News
|July 16, 2008|
Insect stings have been on the rise in Alaska, and experts think that global warming could be to blame.
A recent report shows steady increases statewide in patients seeking medical care for insect stings.
The report also noted that in 2006 two people in Fairbanks died due to anaphylactic shock after being stung by small hornet relatives known as yellow jackets—the first time such deaths have been reported in the city.
"What we are seeing is a tremendous spike in the number of yellow jackets," said study co-author Jeffrey Demain, director of the Allergy, Asthma, and Immunology Center of Alaska in Anchorage.
He and colleagues estimate that in 2006 the town was plagued by ten times more yellow jackets than average.
"We think climate and temperature changes are creating a more favorable environment for their survivability," Demain said. Milder winters and earlier springs, for example, could be helping the insects to thrive.
"[And] the more yellow jackets, the more sting events we see."
Demain and other experts believe this scenario could be part of a worldwide trend of stinging insects spreading northward in response to climate change.
"Many species will migrate north as their ecological niche moves northward, and those movements will be strongest in the highest latitudes," said Robert Correll, global change director of the Heinz Center for Science, Economics, and the Environment in Washington, D.C.
"What drives them is temperature."
Wasps on the Rise
Using a Medicaid database of 132,000 Alaskans, Demain and colleagues saw that sting incidence rates per 100,000 patients went from 346 in 1999 to 455 in 2006.
Regionally, the team saw a sevenfold increase in stings in northern Alaska between 1999 and 2006. In the interior, sting rates per 100,000 patients increased from 260 a year in 1999 to an average of 437 a year between 2000 and 2006.
Initial data from the study appear in the May 2008 issue of the State of Alaska Epidemiology Bulletin.
The report authors note that over the past 50 years, Alaska's average temperature has risen by 4 degrees Fahrenheit (2.2 degrees Celsius)—four times more than the global average.
Shifting seasons, new precipitation patterns, and rising temperatures already seem to be having an impact on insect populations in countries farther south that affect human health.
In Kenya and Latin America, for example, experts are beginning to document a connection between mosquito migrations tied to warming and new cases of vector-borne diseases such as malaria and dengue fever.
(Related: "Climate Change Spurring Dengue Rise, Experts Say" [September 21, 2007].)
While yellow jackets are not vectors for disease, their painful stings can in some people cause anaphylactic shock, an allergic reaction to their venom similar to an asthma attack.
According to the World Allergy Organization, roughly 4 percent of humans are allergic to bees, hornets, and/or yellow jackets. Severe cases can be fatal, with wasps and bees causing 30 to 120 deaths yearly in the United States.
Few scientists have specifically looked for a link between climate change and shifting yellow jacket populations, but there is anecdotal evidence that the insects have been moving north.
In 2004, for example, a Canadian entomologist confirmed the presence of yellow jackets in the village of Arctic Bay, Nunavut, where they had never been seen before.
Yellow jacket workers and male drones only live for a year. For the insects to persist in a region, a fertilized queen must survive the winter and emerge in spring with favorable conditions for building a new nest.
"In terms of recent climate changes in Alaska, the greatest warming has occurred during winter and spring—precisely the seasons to which insect survival is most sensitive," said John Walsh, professor of climate change and chief scientist at the University of Alaska, Fairbanks.
Report co-author Demain said there are many factors that play a role in yellow jackets' ability to thrive so far north, and no one is sure yet which ones are most impacting their boom.
He plans to develop a model to track regional precipitation and temperature variances that could then be correlated with insect-sting data.
A similar initiative called MoveBank, slated to launch in October, may help researchers such as Demain track and predict insect outbreaks.
MoveBank is a free visualization tool that uses data from researchers around the world to plot and view animal migration patterns.
The tool is the brainchild of Martin Wikelski, a zoologist and behavioral ecologist at Princeton University and a National Geographic Emerging Explorer. (National Geographic News is part of the National Geographic Society.)
"We know that things are moving northward," Wikelski said. "But we don't know what individuals are doing and how they decide [where to go]."
"With MoveBank, researchers who study yellow jackets in Alaska could input their data and then match it with global climate patterns and learn how things are changing."
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