Understanding Soil’s Role in Urban Ecology: My Research Experience

In urban environmental studies, the primary quality of soil investigated is soil sealing, or how much of the soil surface is covered by roads and buildings in any given location. While deciding on a project topic for Laidlaw, it struck me how much disconnect there is between ecological and urban planning research specifically on the subject of soil structure and composition. Soil health, or the holistic study of soil qualities and services, is a relatively new field of study focused primarily on agricultural settings. However, with the growing attention to urban green spaces and small-scale biodiversity initiatives, there needs to be more research into the role of soil in the productivity of urban green spaces. A good way to think about it is that soil is the foundation, literally and figuratively, of all ecosystems. Soil functions as both a bank of macro- and micro-nutrients like carbon, nitrogen, and potassium, and as a behind-the-scenes manager of services critical to plant, animal, and fungal life. Without taking the intricacies of soil structures and ecosystems into account, one can never get a complete and accurate picture of the functions of an ecosystem. My project aimed to find a correlation between soil compaction, plant biodiversity, and urbanisation to bridge the gap between urban planning and soil science knowledge.

To answer my research question, I took soil samples and plant diversity data from 21 sites within County Dublin. Sites were selected using Random.org to generate random coordinates which were checked against the Copernicus UrbanAtlas. 21 coordinate pairs falling within Green Urban Areas (14100), Forests (31000), or Herbaceous Vegetation (32000) zones were chosen and run through the Keplab UrbanizationIndex software where a kilometre by kilometre area with the coordinates at the centre were analysed by the percentage of road coverage, building coverage, and vegetation coverage and assigned an urbanisation score between -5 and 5, with 5 being the most urban. As close to the centre of each site, a metre by metre quadrat was tossed and a survey counting unique plant species present in the quadrat. Afterwards, a soil sample was collected from within the quadrat by digging a hole as deep as the diameter of the sample cylinder and inserting the sample cylinder parallel to and less than a centimetre from the soil surface. The sample was then weighed, bagged, baked in an oven at 105° C for 24 hours, and reweighed. From there, the bulk density of the soil samples were calculated, showing the level of compaction, and those results were analysed against urbanisation score and number of unique species per metre squared. There was no statistically significant correlation between any of the values, but trends did match what was expected.

Going into the Laidlaw Programme and my research project, my main goal was to integrate community knowledge into ecology research in Dublin’s context. My proposal specified that, in analysing soil compaction and plant biodiversity across the urbanisation gradient, the urbanisation subgroups would be assigned to sites based on archival land use documents and local oral histories. However, after planning my six-week project span and discussing methodologies with my advisor, we came to the conclusion that the archive search and oral history would eat up too much time. As the project started and I spent days on end collecting soil samples and biodiversity data, more and more people came up to me to ask me what I was doing. Kids would pause their hurling scrimmage to come chat and I’d show them how to take the soil sample, and older men would make sure my work wouldn’t mess up the local park. Even after I removed the social portion of the study, the stories people told about the land they lived on followed me.

Going forward, I hope to investigate the relationship between soils and urban biodiversity more rigorously and to integrate social sciences into my work more intentionally. Strengthening my relationship with fieldwork and the environment as well as connecting with other people passionate about the health of their land has informed my view of leadership as an environmental researcher. It’s easy to assume that people have no emotional stakes in their environment when watching the news or seeing litter and habitat destruction all around us. But in my experience, those apathetic people are in the minority. Urban planning must consider the passion and emotional investment of the communities that exist within an environment and further prioritise human stakeholders in design.
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