Image Credit: Jenn Glaser, ScribeArts
If the last mosquito season felt longer, or if mosquito bites seemed to hurt more than you remembered, you didn’t imagine it! Mosquitoes respond sensitively to changes in heat, humidity, and precipitation, and serve as buzzy, annoying sentinels of our changing climate. Here’s how mosquitoes are letting us know our climate is changing.
With climate change comes an increased frequency and intensity of extreme weather events -- think of this summer’s historic heat dome in the Pacific Northwest, the wildfires in the western U.S., and longer and stronger hurricane seasons on the Atlantic seaboard. But what are the relationships between climate change, extreme weather events, and mosquitoes?
Mosquito seasons are getting longer. In many regions of the U.S. and elsewhere, summers are longer, and winters are shorter, which means there are more days per year when temperatures are over 50 degrees Fahrenheit (10 degrees Celsius). More warm days mean more mosquito generations can be packed into a season, with bigger populations of mosquitoes as an outcome.
Mosquitoes are expanding their ranges. With warming, certain mosquito species, such as Ae. Aegypti and Ae. Albopictus, are expanding their ranges to higher latitudes and altitudes that previously could not sustain the species.
Invasive mosquitoes are increasingly being found far from their original homes. Through globalization and human migration, mosquitoes hitchhike around the world, accompanying people and goods. They are finding new regions where they can establish residence. The Asian Tiger mosquito, an invasive that hitchhiked around the world with the used tire trade in the 1970s, is now actively expanding northward in the U.S. If you have experienced bites this summer that seemed more painful, it may be the first time you have encountered this invasive species where you live. Many describe Asian Tiger mosquito bites as more irritating than those of our homegrown mosquitoes because the Asian Tiger mosquitoes tend to bite more than once in the same spot, creating larger and more painful bite areas.
Mosquito populations respond to extreme weather events. Scientists are making headway in understanding how extreme events impact disease outbreaks. In a recent paper, scientists Cameron Nosrat and others (2021) used satellite and rain gauge data to identify extreme weather anomalies in Kenya. They were able to associate extreme weather events with increases in the Aedes aegypti larvae and adults one month after the event, demonstrating a predictable response of mosquito populations to flooding events. Cold waves, which reduce the ambient air temperatures to near their optimal threshold of 29 degrees C, were also associated with an increase in the abundance of adult Ae. aegypti mosquitoes. Droughts and heatwaves that create drier climatic conditions appear to decrease mosquito abundance.
The impacts of climate change on mosquito populations that we are seeing now are concerning. Scientists warn that increased cases of vector-borne disease are one of the most serious health consequences of climate change. Mosquito-borne disease is on the increase because both the insects and the pathogens they transmit respond sensitively to changes in the environment. Increased temperatures are associated with increased rates of mosquito reproduction, development, survival, and biting rates. Sources of standing water are necessary for reproduction, so environmental conditions that increase the amount of standing water support larger mosquito populations.
While climate change is causing extreme weather events to increase in frequency, vector-borne disease risk models will help us to prepare so that anticipated disease outbreaks can be curtailed or averted. Based on their research, Nusrat and others (2021) point to the usefulness of extreme weather events as an early warning for potential health threats and the importance of targeted interventions in the aftermath to reduce the risk of disease. Observers, with the GLOBE app in hand that supports surveillance and source reduction, are ready to respond when extreme weather comes their way.
To download GLOBE Observer, go here: https://observer.globe.gov/about/get-the-app With the app tool, GLOBE Mosquito Habitat Mapper, observers can help mitigate disease and mosquito populations near them. Always follow local guidelines when using the app.
About the Author:
Dr. Russanne Low is a senior scientist with the Institute for Global Environmental Strategies, Arlington, VA and is the Science Lead for the GLOBE Mosquito Habitat Mapper and the GLOBE Mission Mosquito campaign.
Cited: Nosrat C, Altamirano J, Anyamba A, Caldwell JM, Damoah R, Mutuku F, et al. (2021) Impact of recent climate extremes on mosquito-borne disease transmission in Kenya. PLoS Negl Trop Dis 15(3): e0009182. https://doi.org/10.1371/journal.pntd.0009182