Study: Green infrastructure can spread disease when poorly planned

When designed according to local ecological conditions, green infrastructure can raise property values, provide additional habitats for wildlife, and improve public health. But according to a study conducted by a team of American and Swedish researchers, improperly designed green infrastructure can exacerbate risks to public health. Eric Vance/U.S. Environmental Protection Agency.

Green infrastructure designs that fail to consider the effects of the installation’s placement or the types of wildlife it may attract can increase risks of spreading serious diseases, according to research published in the journal, Ecology and Epidemiology.

“There seems to be a prevailing assumption among the general public that everything that is nature – that is part of wilderness – is good and safe,” said Mare Lõhmus, professor of environmental medicine at Karolinska Institutet (Stockholm, Sweden) and co-author of the study, in a release. “Little thought is given to what can go wrong.”

 

Quality, not quantity

When it comes to green infrastructure, more is not always better.

For example, planting a line of trees along roadway medians can improve stormwater retention and reduce urban heat island effects. But many tree, weed, and grass species also release volatile organic compounds that enter the atmosphere and can contribute to air pollution, according to the study. Installing too many plants, too closely together without considering how emissions from different species will interact can worsen air quality and spread pollen allergens. If tall enough, urban vegetation also can limit air circulation, the researchers write.

Constructed wetlands carry similar risks. While wetlands developed in strategic areas can help mitigate flooding and improve local water quality, they also create new areas where toxic algal blooms can flourish. If sited closely enough to recreational waterways or drinking water sources, these wetlands can imperil the health of both humans and wildlife, the researchers write.

“I love that we are seeing more green spaces in urban settings, but we need to be aware of the potential negatives and plan accordingly,” Lõhmus said.

 

Biodiversity is not always a plus

Many green infrastructure planners incorporate plant species known to attract certain “beneficial” wildlife species, such as butterflies and other pollinators. But benefits to wildlife do not always benefit humans, the researchers write.

Designing green infrastructure installations with certain types of plants or connecting separate green spaces across busy roadways can enable rats to access parks and other recreational areas more easily. As rats often carry disease-causing pathogens, increasing their mobility can threaten human health, according to the study. Pxhere/Public domain.

Depending on local climatic conditions, the same plants that attract pollinators may also attract ticks, rats, mosquitos, and other pests capable of spreading disease. As the effects of climate change gradually become more apparent, the researchers write that predicting how green infrastructure might affect biodiversity and public health may become more important – and more difficult.

For example, while connecting urban green spaces can create attractive park networks and manage stormwater over a larger area, it also enables pests to migrate. Rats stay away from busy roadways and naturally move toward water. By providing a means to circumvent roadways, connecting green spaces can increase risks of attracting rats – and such pathogens as Escherichia coli and Cryptosporidium – to parks and recreational spaces.

Drawing from several European cities that have undertaken urban green infrastructure campaigns, the researchers describe how increasing rat mobility led to upticks in red foxes spotted in urban areas. The small fox tapeworm, a parasite that can cause health defects in humans, also experienced an uptick in these cities.

“While increased biodiversity and more natural milieus are welcome features of the cities of the future, it is important to think about the potential disease vectors and pest organizations that may thrive if [green infrastructure is] created without careful planning,” Lõhmus said.

 

Takeaways for green infrastructure planners

Green infrastructure planners should involve ecologists and public health experts early in the design phase to ensure stormwater management improvements do not come with unintended consequences, the researchers advise.

Among other recommendations highlighted in the study, planners should

  • identify local public health risk factors, such as prevalent diseases and common carriers of those diseases, before breaking ground on new infrastructure projects;
  • consult with public health officials to raise awareness about potential pests attracted by green infrastructure installations using signage or other outreach materials;
  • avoid installing fruit-bearing bushes and trees in new infrastructure, as these can attract rats; and
  • use pond pumps, waterfalls, fountains, aerators, or other features in constructed wetlands to keep the water from becoming stagnant.

Read the full study for more recommendations on designing ecologically responsible green infrastructure.

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3 Responses to “Study: Green infrastructure can spread disease when poorly planned”

  1. David Rutter
    July 15, 2019 at 11:46 am #

    Your headline is a bit misleading. The study did not actually look at what happens with green infrastructure and instead extrapolates and infers the potential for impacts from green infrastructure (GI) based on other research in related areas but not directly linked to GI.

  2. Shaun
    July 18, 2019 at 11:29 am #

    From the abstract, my CAPS:

    “This paper considers several POTENTIAL harmful public health effects that MIGHT result from increased urban biodiversity, urban bodies of water, and urban tree cover projects.”

    This paper does nothing to monitor, document, study, or quantify—in any way—whether or not green infrastructure does anything, let alone spread disease, and is really silly, at best, or alarmist at worst. This may come as a shock to some folks, but this isn’t anything that professionals don’t already know.

    I’m surprised, gobsmacked even, that they didn’t mention the disastrous effect that green infrastructure would have on a thermonuclear bomb attack. All those trees and open spaces might allow for the creation of additional radioactive ash fallout, may not mitigate the impact or propagation of blast waves, and how all that greenery might contribute to the appearance of a decadent, privileged, and bourgeois lifestyle that make such ideal targets.

  3. Kaleena Menke
    July 24, 2019 at 3:50 pm #

    ^^ You’re my hero, Shaun.

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