In the rapidly urbanizing world we live in, urban green spaces such as parks and gardens serve as vital connections to nature for city dwellers. Not only do these green areas contribute to our physical and mental well-being, but they also play a crucial role in regulating heat waves, floods, and carbon sequestration.
However, until recently, the factors affecting carbon sequestration in urban green spaces remained largely unknown, leaving considerable uncertainty in future predictions about the magnitude of carbon sequestration in these ecosystems.
A groundbreaking study led by the BioFunLab research group sheds light on this critical issue, as they collected samples from 56 cities across all continents. The study emphasizes the importance of urban green spaces as carbon reservoirs, with soil carbon levels equivalent to those found in natural areas near cities.
“Our study shows that urban parks in green spaces around the world have an equivalent amount of carbon in the soil to natural areas near our cities, highlighting the role of our parks in a context of climate change,” said lead author Manuel Delgado Baquerizo.
The research also reveals that the carbon stored in natural areas and urban parks is controlled by similar climatic factors. “Warmer cities have lower soil carbon content in urban parks and natural ecosystems, which is not good news in our fight against climate change in a warmer world,” said Delgado Baquerizo.
However, the researchers found that carbon levels in cities and natural areas are regulated by different biological factors. While carbon in natural areas is closely linked to the primary productivity of the ecosystem, soil microbes play a crucial role in determining carbon levels in urban parks and gardens.
Tadeo Sáez, a member of BioFunLab and co-author of the paper, explained that ecosystem management, such as mowing, is essential in explaining carbon sequestration in urban green spaces. “Our study demonstrates that soil microbes are the main drivers of carbon in urban areas.”
The researchers also discovered that the role of microbes as carbon regulators in urban parks has its drawbacks. “Carbon in park and garden soils is more vulnerable to loss through microbial respiration in response to global warming,” said Delgado Baquerizo. “These soils have a high proportion of genes associated with the decomposition and mineralization of organic matter,” added Tadeo Sáez.
Given the importance of urban parks as carbon reservoirs in a world where seven out of ten people will live in cities by 2050, the researchers conclude that future parks and urban policies should take soil microbiomes into account to maintain soil carbon and its capacity to support multiple ecosystem services, as well as the sustainability of our parks.
“Our study demonstrates the importance of parks as carbon reservoirs in an urbanized world, where 7 out of 10 people will live in cities by 2050. Future parks and urban policies should take into account the soil microbiome to maintain soil carbon and its capacity to maintain multiple ecosystem services as well as the sustainability of our parks,” said Delgado Baquerizo.
The proportion of the population with access to urban green spaces can vary significantly depending on the city, country, and region in question. However, the World Health Organization (WHO) recommends that urban residents should have access to at least 9 square meters of green space per capita, and that green spaces should be within a 15-minute walk (or 300 meters) of every resident’s home.
It’s essential for city planners and policymakers to prioritize the creation and maintenance of urban green spaces, as they contribute to the overall quality of life, promote physical and mental health, and offer environmental benefits such as carbon sequestration and heat regulation.
The research is published in the journal Nature Climate Change.
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