What is the secret ingredient in the green infrastructure of the future?

By Gabrielle Stannus
Adelaide could be Australia’s new biodiversity ‘hotspot’ with local researchers suggesting that parks of the future may be designed with microbes in mind.

Many people working in the greenlife industry realise that urban green spaces can provide biodiversity and health benefits. However, fewer people are perhaps aware of the close relationship that biodiversity, especially at a microbial level, has with our mental and physical health.

More than just ‘Old Friends’

Professor Philip Weinstein, Professorial Research Fellow at the University of Adelaide’s Environment Institute, says humans have evolved in green spaces, co-existing with a diversity of plants, animals and microbes, e.g. bacteria, fungi and archaea. This is known as the ‘Old Friends’ hypothesis.

“If you take us away from that environment, our immune system does not get trained appropriately by exposure to a whole range of microbes and then it can get lazy and over-reactive. So, if a pollen grain or something comes along and hits an urban kid with an immune system that is not appropriately trained, the kid has an asthma attack and says, "Ooh, you know, what's this foreign body? What is this pollen?" And it overreacts because it is bored. In a kid who has grown up on a farm that does not happen because that child is constantly being exposed to biodiversity, microbially, plant, animal, the whole lot. And the immune system knows that "Hey, this pollen or animal antigen or bacterium is normal. So, it does not overreact. And for that reason, there is a much lower rate of asthma and other allergic diseases in kids who grow up in rural environments than there are in kids who grow up in cities,” explains Philip.

Growing urban population

Dr Martin Breed is an Ecology Lecturer at Flinders University and a co-lead with Philip of the Healthy Urban Microbiome Initiative (HUMI). With the United Nations predicting that more than more than two-thirds of the world population will live in cities by 2050, Martin claims urban green spaces will become even more important for realising improved public health outcomes.

“In many cities in Australia and in fact globally, the amount of urban green space is declining. In cities like Adelaide, a lot of that is driven by private land subdivision, leading to a decline in greening value,” says Martin. Whilst Martin calls for more public and private urban green spaces, he says that it must be the right type of green space if it is to increase human interaction with microbes. Urban spaces are generally degraded, lacking microbial diversity compared to remnant vegetation sites. Therefore, HUMI is leading the way in researching novel ways to restore microbial diversity into urban green spaces.

Microbiome-Inspired Green Infrastructure

Jake Robinson, a PhD candidate from the University of Sheffield, is currently conducting work with HUMI researchers. Together, they are investigating how green infrastructure could be designed to promote beneficial interactions with health-promoting microbiota, i.e. Microbiome-Inspired Green Infrastructure. Jake’s research is based on the premise that biodiverse microbial habitats can be ‘restored’ as per the microbiome rewilding hypothesis. This hypothesis posits that restoring biodiverse habitats in urban green spaces can rewild the environmental microbiome to a state that helps prevent human disease as an ecosystem service3. A microbiome is the consortium of micro-organisms such as bacteria, fungi and archaea found within a given environment, e.g. air, water, soil.
Jake is investigating the factors influencing human and environmental microbiome interactions including sociodynamics, species composition, vegetation structure, physiochemical substrate parameters, aspect, climate, physical (building) features, pollution and land use.
“I am currently looking at different land cover types and vegetation communities and how configurations of those may affect the aerobiomes (the microbiome in the air) to which we are exposed to every day. Wind and pollution are big factors in dispersing microbes across urban areas,” says Jake. Jake is investigating whether vertical stratification of microbes exist in the aerobiome. He is trying to determine whether there is a type of decay in the microbial communities from the ground upwards and whether vegetation management would affect this decay. The results of this research may have implications for the future design of Microbiome-Inspired Green Infrastructure, e.g. plant selection and placement in green walls.
Philip adds: “There may be some plants that are better than others, i.e. they are rich with microbes or increase soil diversity of microbes more rapidly than others. However, we do not yet know specifically what those plants or animals or microbes are.”

In the meantime, Philip cautions that the only thing he and his fellow researchers can say with reasonable confidence is that diversity is good.
“You can only achieve that biodiversity by having plants available to put into those areas too, so that they are not just green lawns but genuine functioning ecosystems,” says Philip.
Martin says that Microbiome-Inspired Green Infrastructure may also mean increased demand for soil-related products, including soil inoculants, custom-made scalable substrates for outdoors or even non-soil substrates for indoor use. These products may include living microbes or potentially the products of these microbes, e.g. metabolites or antigens, the latter which may be more palatable to consumers concerned with potential health and safety risks. All these products would require further research and a serious risk assessment before they could enter the market.
Stay up to date
Follow @_Jake_Robinson and @_MBreed on Twitter for news on their latest research results.

1. Ritchie, H & Roser, M 2019, ‘Urbanization’, Published online at OurWorldInData.org, viewed 15 December 2019, https://ourworldindata.org/urbanization#what-share-of-people-will-live-in-urban-areas-in-the-future
2. Mills, JG, Brookes, JD, Gellie, NJC, Liddicoat, C, Lowe, AJ, Sydnor, HR, Thomas, T, Weinstein, P, Weyrich, LS & Breed, MF 2019, 'Relating Urban Biodiversity to Human Health With the ‘Holobiont’ Concept', Frontiers in Microbiology, March 2019, Vol. 10, Article 550
3. Robinson, JM, Mills, JG & Breed, MF 2018, 'Walking Ecosystems in Microbiome-Inspired Green Infrastructure: An Ecological Perspective on Enhancing Personal and Planetary Health', Challenges, vol 9, iss 40, November 2018
4. Robinson, JM & Jorgensen, A 2018, ‘Rekindling Old Friendships in New Landscapes: The Environment-Microbiome-Health Axis in the Realms of Landscape Research’, People and Nature, manuscript submitted.
5. Our World in Data, ‘Share of the population living in urban areas, 2050’, viewed 15 December 2019, https://ourworldindata.org/grapher/urban-population-share-2050