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Using urban planning to reduce mosquito-borne disease

Urban development in coastal Australia brings people closer to mosquito habitats while often also creating new wetlands. Webb, Medical Entomology

There are many ways to prevent mosquito-borne diseases – insecticides to kill mosquitoes, vaccines to prevent infection and healthy doses of insect repellent before heading off for fishing trips. But while each of these strategies can play a part, where we live and how we build our communities may have an even greater effect.

More than 5,000 Australians are struck down with mosquito-borne disease every year, mostly caused by the Ross River or Barmah Forest viruses. The La Nina conditions along eastern Australia in recent years have also brought with them the re-emergence of the potentially fatal Murray Valley encephalitis virus.

There’s much discussion about the potential impact of climate change on mosquito-borne disease risks but, in fact, urbanisation will influence the activity of zoonotic diseases (diseases passed from animals to humans) even more by disturbing local ecosystems and biodiversity.

Moving closer to mosquito habitats

Most Australians want to live on the coast, and local authorities face pressure to release land for new residential developments. These new areas are often in close proximity to wetlands, which are already home to plenty of bloodthirsty residents. And it isn’t just the increasing number of mosquito bites that are the problem. A lack of awareness among new residents about the health risks posed by local mosquito populations may also increase the rates of disease.

Building residential developments close to estuarine wetlands inevitably leads to pest mosquito problems. Russell, Medical Entomology

Given we plan for environmental hazards such as bushfires and floods, why not mosquitoes? The mozzies, as well as the viruses and the animals (kangaroos, wallabies and birds) that carry them, are a natural part of the Australian environment. To reduce the risks of mosquito-borne disease, authorities need to juggle the management of mosquitoes, the environment, wildlife and people.

Some local governments in New South Wales have led the way in developing strategies to address these risks. Almost 20 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 remain a key component of local planning.

Similarly, Ballina Shire Council has introduced planning instruments to encourage developers to turn their mind to the risks associated with local mosquito populations. Rather than prevent development, these strategies are designed to guide urban planning.

Earlier this year, Byron Shire Council adopted a mosquito management plan that identified areas of mosquito risk, based on local mosquito populations and wetland areas. The plan includes recommendations to reduce mosquito risk through simple building design features such as the provision of screened outdoor areas as well as development site layout and landscaping to incorporate buffer zones between adjacent mosquito habitats and residential allotments.

Constructed wetlands for water treatment, storage and wildlife habitat are commonly incorporated into new residential developments. Webb, Medical Entomology

Creating new habitats

Concerns over water conservation are once more being raised as the east coast of Australia approaches another hot and dry summer under the influence of prevailing El Niño conditions. Water-sensitive urban design can integrate water conservation into urban developments through the use of rain water tanks, rain gardens, bioretention swales and constructed wetlands. But each of these elements risks the creation of new mosquito habitats.

The potential for rainwater tanks to provide habitat for mosquitoes, including species that spread dengue can be easily reduced. Perhaps a greater issue is other water hoarding behaviour. Uncovered buckets, bins and other containers to catch and store rainwater are more likely to produce mosquitoes.

For constructed wetlands designed to catch and store storm water run off, mosquito control can be more problematic. Such wetlands are often built with many purposes in mind. Reducing the pollution in storm water run off, creating wildlife habitat and providing some pleasant surroundings for passive recreation are just a few. Meeting these objectives while keeping mosquitoes in check is difficult.

Local authorities should ensure that wetlands are based on guidelines for reducing suitability for mosquitoes as part of the planning and approval process. More importantly, there has to be an adequately funded management plan in place to ensure that wetlands are clear of overgrown vegetation and sediment that may increase the production of mosquitoes.

Reducing the risk of mosquito-borne disease takes more than just managing mosquitoes. We need to look at how humans, wetlands and wildlife all interact, particularly in new urban developments.

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