Bugged By Climate Change

Sep 25, 2019

File photo of a mosquito carrying Eastern Equine Encephalitis
Credit Rick Bowmer / AP Photo

Does an uptick in diseases like Eastern Equine Encephalitis spread by mosquitoes have anything to do with climate change? A researcher at Western Michigan University says it probably does.


(UPDATE: The state health department says it will begin overnight aerial spraying to control mosquitoes spreading Eastern Equine Encephalitis on Sunday, September 29, in 14 counties, weather permitting. The affected area includes Kalamazoo, Calhoun, Allegan, Van Buren, Saint Joseph, Barry, and Cass counties. The department says the spraying by low-flying aircraft will target "high risk" areas. It says the chemical used will not harm most people and pets, but it also says those sensitive to insecticides should remain indoors. The decision has drawn criticism. Kalamazoo Mayor Bobby Hopewell says he would prefer a more "targeted" approach rather than spraying large areas. To date, there have been nine human cases of EEE in southwest Michigan and three people have died after getting the disease.)

Biologist David Karowe says the question about how insects like crickets and mosquitoes will fare as Michigan gets warmer and probably wetter has two answers. The first is that many will probably do great - in the short-run.

"Because the two main components of climate, both of which have been changing - temperature and precipitation - have actually been changing in ways that make Michigan more hospitable to mosquitoes in general, and actually promote the development of the virus inside the mosquito."

Karowe says the shifting climate is already making Michigan and other states more welcoming for certain insect pests.

"We're seeing things like outbreaks of pine beetles in the Northwest and in Canada, almost certainly due to increased over-wintering survival, which is almost certainly due to higher winter temperatures."

But Karowe says, long-term, the vast majority of insects will be "climate losers" as the changes interfere with their life cycles. That's because insects stop eating and begin to enter their form of hibernation as the days grow shorter. But as temperatures stay warmer for longer periods, that forces them to burn resources they need before winter sets in.

Karowe says more studies are needed on climate change and mosquitoes like the ones spreading diseases like Eastern Equine Encepalitis and West Nile virus. But he says a near certainty that short-term effects of climate change will mean larger populations of bugs, "good" and "bad."

"For disease vectors, certainly, that's bad. For crop pests or forest pests that's bad. But for pollinators, who have a slew of other problems, at least the over-wintering survival should increase a bit in the short-run due to climate change."

Karowe says climate change has definitely led to the spread of Lyme disease in Michigan. That's because the warming temperatures and more rain encourage the spread of the black-legged tick and the white-footed mouse that carry the disease.

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