The prevalence of mosquito-borne disease has plagued urban communities for decades, prompting scientists to look to stormwater infrastructure for sustainable solutions. Brian Allan, Professor of Entomology at the University of Illinois Urbana-Champaign, leads an iSEE-supported research project exploring the use of environmentally sustainable “green infrastructure” to eliminate standing water environments necessary for mosquito larvae survival.
Existing stormwater infrastructure is typical in many urban environments, designed to capture and retain stormwater and prevent flooding. However, from an ecological standpoint, these catch basins are prime environments for urban mosquitoes to lay their eggs, thrive, and promote vector-borne disease outbreaks.
“Not only are we creating a ton of mosquito habitat, but it’s all physically disjunct,” Allan said. “From a management perspective, if you want to try to control the mosquitoes developing in those habitats, you have to go from catch basin to catch basin and put pesticides for mosquitoes in them, and there are millions of these basins in a city like Chicago.”
Conventional stormwater infrastructure causes other issues, too: Pollutants from the urban environment, such as oil from cars, sit in the basins until rain flushes them into surface waters, contaminating rivers, lakes, and streams.
Green infrastructure is an engineering innovation designed to intercept the stormwater on-site. Unlike traditional catch basins, green infrastructure designs have permeable bottoms that allow the water to filter back into the soil.
Allan and his colleagues saw this existing sustainable solution as an opportunity to study how it might prevent mosquito growth — a potential “win-win” scenario. His team decided to investigate locations where green infrastructure was implemented to see if habitats for mosquito development decreased. Additionally, they were curious about the composition of the aquatic microbiome and how this impacted mosquito growth.
“We are very familiar with the microbiome inside our bodies,” Allan said. “Mosquitoes have a microbiome as well … there’s potential that the microbiome can be manipulated in some way that’s not beneficial to mosquitos.” The area around the basins could play a key role in altering the microbiome composition of the mosquitoes, as the leaves are dropped and washed into the stormwater catch basin. The microbes that break down these leaves are a food source for mosquitoes and may result in different mosquito microbiomes forming.
On the basis of this observation, Allan’s former Ph.D. student Allison Gardner introduced leaves from different plants into the basins. She found that leaves from non-native plants, like bush honeysuckle, a common invasive species in eastern North America, were ideal for mosquito development. However, blackberry, a native species, had the opposite effect. Blackberry leaves created what is known as an “ecological trap.” Female mosquitoes expect that aquatic habitats containing blackberry leaves have optimal conditions for their larvae’s growth, but when they lay eggs in these habitats, the microbial growth there is detrimental to larval survival. “It looked to be an organic form of mosquito control,” Allan said; blackberry leaves appear to be just as effective as larvicides.
The sustainability of green infrastructure and the mosquito control component are parallel functions.
“We’re looking to bring them together, particularly in the context of rain gardens, because rain gardens are one of the forms of green stormwater infrastructure that eliminates the aquatic habitat for larvae, but they’re also landscaped with various plants,” Allan said. His research team hopes to explore the potential for mosquito control through landscaping rain gardens with plant species, such as blackberries, that inhibit larval growth.
As Allan describes it, prioritization of human health can be used as a tool in sustainability: “If you can do something that benefits people’s health, they’re much more likely to support an environmental solution than one that doesn’t benefit human health.”
One current aim of the project is to analyze the effects of rain barrels, a standard green infrastructure tool that might negatively impact human health. They are becoming popular green stormwater tools for homeowners, who buy these barrels, hook them up to a gutter system, and reuse the water that is collected. While a good idea for water conservation, the barrels can quickly become colonized by mosquitoes. An analysis of a residential rain barrel survey by current Ph.D. student Becky Cloud indicates that the main culprit is the debris screen that tops the barrels. Most homeowners find that the screen gets clogged and end up removing it early in their ownership. However, as the primary barrier between the water and mosquitoes, the screen’s removal is actually quite harmful. The simple solution is to clean the screen and reapply it.
This finding gave Allan and his team the motive to engage in community outreach to explain the science behind green infrastructure.
“I think that’s an example of where I feel, as a scientist, an obligation to communicate my findings to the public,” Allan said. “If I just publish that in a journal that only other scientists will read, that’s really not the most useful thing I could do.”
Educating the community about sustainability, green infrastructure, and mosquito-borne diseases is necessary to elicit change. The public is much more likely to support causes that are both sustainable and beneficial to human health, and discovering more of these “win-win” scenarios is an important motivating factor of research today. Inspiring the community through education can lead to collective action and a more harmonious co-existence between urban society and nature.
Allan has taken an active role at iSEE in helping to organize two major events: a 2019 Critical Conversation on genetically modified mosquitoes, which resulted in a widely read op-ed piece in The Conversation; and the most recent iSEE Congress in Spring 2023: “Addressing Crises of Planetary Scale: Lessons from Pandemics and Climate Change.”
The Stormwater & Mosquito Control Project was funded by a seed grant from iSEE in 2015 and has since been extended with two major National Science Foundation awards and a U.S. Geological Survey grant.
For more information and updates, check out iSEE’s Stormwater & Mosquito Control Project page >>>
— Article by Anjali Yedavalli, iSEE Communications Intern