A new study of urban green spaces around the world has found they contribute to the filtering of pollutants and carbon dioxide sequestration via the microbial communities they harbour.
The ‘Global homogenization of the structure and function in the soil microbiome of urban greenspaces’ study took soil samples from 56 cities in 17 countries across six continents.
It found, among other things, that city parks and gardens play an urban role in curbing pollution, lowering noise and reducing temperature.
Furthermore, human exposure to soil microbes is shown to be beneficial to health as it promotes effective immunoregulation functions and reduces allergies.
Green spaces support fast-growing microbes that use fertilisers and irrigation water, and can colonise bare soils. Fungal root pathogens, such as Fusarium, and bacteria-feeding amoebae are examples. Fungal root pathogens are microorganisms capable of removing nitrogen from sewage.
Green spaces, the study found, also harbour a greater proportion of fungal parasites and plant pathogens, which are often economically important pests. In some countries, green spaces host microbes linked to human pathogens, such as listeria and diphtheria.
“Parks are not the homogenised ecological deserts that we think they are,” says study co-author professor David Eldridge from the Centre for Ecosystem Science in UNSW Science’s School of Biological, Earth and Environmental Sciences. “They are living ecosystems that do amazing things.
“Urban green spaces harbour important microbes, so if you want to sustain a bunch of ecosystem services, you need to have plenty of parks and green spaces,” he adds.
The results mirror a study in Central Park in New York, says Eldridge, which found there was as much microbial diversity in the city park as there is globally. “City parks harbour a range of microbial communities that are different to natural ecosystems.”
Even the humble nature strip has a role to play. The study found a great variety of different microbes in some roadside verges. “They are not barren wastelands at all,” says Eldridge.
“Some European cities, such as Bern in Switzerland, have a policy to protect the natural vegetation along footpaths and roadsides. These pathways then become mini green spaces, linking larger green spaces. We need lots of different microbes and to get this we need a variety of landscapes such as median strips, parks and nature reserves.”
Interestingly, green spaces from around the world presented very similar results in the study. “They often have lawns, and similar management practices, which tend to homogenise the microbes living in different global cities,” says lead author Dr Manuel Delgado-Baquerizo.
Urban green spaces are critically important for promoting mental and physical well-being in our urban hubs, with the UN Department of Economic and Social Affairs predicting that 68 percent of the global population is set to live in cities by 2050.