Governments, urban designers, professionals and communities are starting to take notice of the growing threat of disease spread by mosquitoes. Considering mosquito habitat is an important aspect of urban design that should come hand-in-hand with climate adaptation. Here’s what can be done.
This is Part 2 of a two-part article series.
Read Part 1 here: And now for the mosquito borne disease threat to our warming cities
Dr Cameron Webb is a mosquito expert and clinical associate professor of medical entomology at NSW Health Pathology and the University of Sydney. In the more than 25 years since he has been researching mosquito borne diseases, it is only in the past few years that authorities, designers and communities have started to take notice.
Governments, designers, and individuals are increasingly taking the issue seriously, and seeing it as an important aspect of urban design that should come hand-in-hand with climate adaptation.
In light of increasingly severe climate change flood events, the COVID-19 outbreak, and now the outbreak of JEV, urban professionals have started to discuss how urban spaces can be designed and managed to reduce mosquito populations and prevent ensuing disease outbreaks.
“Mosquitos are going to be yet another challenge we face as we move forward into our future cities under the impact of a changing climate”– Dr Cameron Webb
“The COVID pandemic has reinforced our understanding of public health and infectious diseases, and that extends to mosquitos.
“There are definitely more people interested in how we can design our cities to reduce opportunities for mosquitos,” he said. “The important thing is that there’s a greater understanding that we can improve the health of the environment, while at the same time reducing mosquito populations – you don’t have to choose between the two.”
Some of the work he has done suggests that large mosquito populations can be a symptom of the poor health of the environment.
“Some wetlands have become degraded and become unhealthy because water doesn’t flow through it very well. Restricting the flow of water in urban areas creates a stagnant environment that is the ideal environment for mosquitos.”
Periodically flushing out these wetlands and reservoirs can create a healthier ecosystem for other flora and fauna to revive, while at the same time reducing mosquito numbers. This technique is in use at Sydney Olympic Park which, in collaboration with scientists from NSW Health Pathology, periodically deploys tidal flushing of degraded salt marsh meadows and mangrove forests along the Parramatta River. As a result, over the past 20 years mosquito populations have reduced.
How can we design out mosquitos from our cities?
“Local authorities should integrate mosquito management in the way that we build and run our cities, so it’s not seen as separate, but a critical part of how we manage our local areas,” Dr Webb said.
“Rainwater tanks need to be regulated and maintained. And wetlands in cities reduce pollution and store water, but we don’t want them to become an opportunity for mosquitos.
“When building wetlands and stormwater infrastructure, be mindful that mosquitoes can be a problem, and design accordingly. There’s subtle ways that water can be designed to make them less suitable, like maintenance schedules on plants and wetlands, and reducing large storage devices in stormwater solutions that might be a habitat for mosquitos.”
There’s no one size fits all solution to this problem – it’s a combination of design methodologies and maintenance.
“Local authorities should integrate mosquito management in the way that we build and run our cities, so it’s not seen as separate, but a critical part of how we manage our local areas”– Dr Cameron Webb
It is rare for local councils to require new developments to mitigate mosquito risk.
In Ballina, planning instruments are in place to encourage developers to turn their minds to the risks associated with local mosquito populations.
New developments are required to do things like properly screen windows and balconies close to wetlands, and in some cases incorporate buffer zones between wetlands and residential development to reduce opportunities for mosquitos. They’re not designed to eradicate mosquitoes, only to reduce them.
Byron Shire Council has also adopted a similar mosquito management plan. This is an area that has been hit hard by floods in recent weeks, so it remains to be known what will be done to protect locals against the rising mosquito population boom that will arise in the aftermath of the floodwaters.
Fly screens, which provide passive cooling while also keeping out pests like mosquitos, are not common in Australian homes, especially rental homes (renters make up 32 per cent of Australian households, according to the Australian Bureau of Statistics).
“Things like fly screens are very clearly part of making a home habitable,” explained chief executive officer of Tenants Union, Leo Patterson Ross.
“It’s a clear example of something that should be done but is often not included in rental homes.”
Another pest mitigation adaptation, screens on greywater and rainwater tanks prevent mosquito breeding, but are “unusual”.
Mr Ross said that when it comes to rental homes, the risk of a no-grounds eviction disincentives people from asking for these adjustments to their properties.
What built environment and natural systems maintenance programs need to be in place?
Twenty years ago, Tweed Shire Council formulated strategies, prepared in accordance with section 72 of the Environmental Planning and Assessment Act 1979, to address the impact of biting insects. These are still a key component of local planning.
The council carries out mosquito larvae control programs during warmer months, using CO2 light traps to monitor mosquito species, modifying the habitat in semi-tidal salt marsh areas, and using biological larvicides deployed by aircraft or on the ground following heavy rain or higher than usual tides. The council is part of a joint mosquito research and information exchange program with Gold Coast City Council, Logan City and Redland Shire Councils.
Sydney Olympic Park also uses chemical spraying of the bacterium Bacillus thuringiensis israelensis (Bti) in mosquito breeding hotspots. Aerial helicopter treatments and ground-based spraying occur within the tidal wetlands of Newington Nature Reserve and Badu Mangroves, just after a high tide event or after heavy rains, when peak hatching occurs.
- Modifying the habitat in semi-tidal salt marsh areas
- Implement planning instruments and regulations such as requiring fly screens, buffer zones between wetlands and developments, screens on greywater and rainwater tanks
- Spraying or “fogging” with biological larvicides by aircraft or on the ground
- Periodical flush out of wetlands and reservoirs
- Monitoring mosquito populations using CO2 light traps
- Emptying bodies of stagnant water around residential areas, using insect repellant, and fans in residential buildings
“We may hate mosquitos,” Dr Webb said in his Ted X Talk Parramatta in 2019. “But we need to understand them. Because if we can’t understand the diversity of mosquitos and their relationships with the environments we’re creating in our greening cities, it’s going to become a much greater struggle to reduce the burden of disease that might come with them.
“And unfortunately mosquitos are going to be yet another challenge we face as we move forward into our future cities under the impact of a changing climate.”
“We can’t be complacent about mosquitos and health risks.”