Urban Parks in the Face of Climate Change: How to Connect Soil, Biodiversity, and Mental Health

What should urban parks of the future look like in the face of climate change? Discover how the BioWater project studies the connections between biodiversity, water retained in the soil, and our mental and emotional well-being.

[This text was co-written by Elsa Carbonell, field technician, and Albert Bach, postdoctoral researcher.]

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When you enter a park after a stressful day, what makes you feel better? The shade of the trees? The chirping of birds? The feeling of being surrounded by nature? Or the combination of freshness, nature, and calm that makes that park function as something more than just a place to pass through?

In a context of climate change, water scarcity, and urban growth, green spaces can no longer be understood merely as recreational areas or as elements with a single function. They are urban infrastructures that can simultaneously contribute to retaining water in the soil, hosting biodiversity, improving environmental comfort, and fostering the mental and emotional well-being of citizens.

The urban parks of the future will have to respond to many challenges at once. BioWater provides a baseline to think of them not as separate pieces of greenery, but as living spaces where soil, water, biodiversity, and well-being are interwoven.

With this vision in mind, the BioWater project emerged as a pilot test developed in ten urban green spaces in Barcelona. The goal has been to explore how vegetation characteristics relate to three key dimensions: soil water content, biodiversity, and the mental and emotional restoration of the people who use these spaces.

How Do Vegetation Characteristics and Soil Moisture Relate to Each Other?

The project has studied parks with different vegetation configurations: spaces dominated by herbaceous plants, shrubs, trees, and mixed combinations of vegetation. It has also incorporated various biodiversity indicators, such as birds, lichens, and hoverflies. Hoverflies are pollinating insects, often resembling small bees or wasps, which can provide information about habitat quality. Additionally, the project gathered the perception of users through surveys and participatory sessions.

The results of BioWater suggest that, in order to generate more resilient green spaces, it is necessary to better understand soil characteristics, restore it, and improve its water retention capacity.

One of the main results is that the relationship between vegetation and soil moisture is not as simple as it might seem. In the parks studied, soil moisture was primarily associated with soil characteristics (soil texture and temperature), environmental conditions such as relative humidity, and vegetation.

This is especially important in a city like Barcelona, where urban green management has been conditioned by drought. The results of BioWater suggest that, to generate more resilient green spaces, it is necessary to better understand soil characteristics, restore it, and improve its water retention capacity.

How Do Vegetation Characteristics Relate to Biodiversity?

In the case of biodiversity, the results also point to a nuanced interpretation. Spaces with a greater richness of shrubs and trees tend to feature a greater richness of birds. However, the biodiversity perceived by citizens does not depend solely on the total number of plant species. In the analyzed parks, the biodiversity perceived by citizens seems to be associated with spaces where vegetation is distributed across a greater diversity of layers and heights, and where these layers have a well-represented coverage (structural complexity of vegetation). Perceived biodiversity was also associated with a greater sense of naturalness.

How Do Vegetation Characteristics Relate to Our Well-Being?

This point is crucial: the way people perceive a green space is also part of its urban function. A park may have ecological value, but for it to be experienced as a restorative space, we must consider how people move through it, how they spend time there, and which elements foster a sense of nature.

The results on mental well-being point in this same direction:

• Mental restoration is associated with the structural complexity of vegetation, perceived naturalness, and connection to nature.
• Emotional regulation through nature—meaning the use of green spaces to calm down, reduce tension, or feel more energized—shows a more consistent relationship with total species richness.
• The length of time spent in the park seems particularly relevant to achieving calmness.

The main conclusion is that parks should not be planned by looking at a single variable. It is not just about increasing vegetation, nor just about maximizing biodiversity, nor just about creating pleasant spaces. The challenge is to integrate these dimensions.

How Should Parks Be Planned, Then?

The main conclusion is that parks should not be planned by looking at a single variable. It is not just about increasing vegetation, nor just about maximizing biodiversity, nor just about creating pleasant spaces. The challenge is to integrate these dimensions.

1. Vegetation, soil, and water must be considered together. This implies incorporating soil diagnosis into the design and maintenance of green spaces, reducing bare soil, encouraging protective organic covers, and exploring nature-based solutions for water catchment and storage.
2. More diverse, heterogeneous, and naturalized spaces must be promoted, avoiding overly homogeneous configurations and combining herbaceous, shrub, and tree layers according to the conditions and uses of each space.
3. Parks must be designed for daily use and well-being: providing shade, paths that are not just transit zones, resting spots, spaces for calm, meeting areas, and infrastructure for care and comfort, such as benches, public restrooms, lactation rooms, or spaces adapted for children, the elderly, and caregivers.

Finally, since BioWater is a pilot test, these guidelines should initially be applied in sentinel spaces or pilot actions, followed by monitoring. This would make it possible to verify which measures work best before expanding them to other areas of the city.

The urban parks of the future will have to respond to many challenges at once. BioWater provides a baseline to think of them not as separate pieces of greenery, but as living spaces where soil, water, biodiversity, and well-being are interwoven.

This study was carried out within the framework of project 24S05864-001, funded by the Barcelona City Council through the 2024 Young and Emerging Research Grant.