5 minute read
Soil and ecosystem services: What does the research say?
The way soils are treated in urban environments has profound impacts on the ecosystem services they provide. Integrating sustainable drainage systems (SuDS) helps to build urban soil health, contributing to flood and urban heating resilience. Read more in the Winter 2023–24 ‘Water’ edition of Landscape © AtkinsRéalis.
The role of soils in ecosystem services clearly demonstrates their value as a multifunctional asset that supports all aspects of life. However, their sustainable management in urban environments is a knowledge gap that must be closed through greater collaboration.
Soils support the functions that maintain life. Its components can be described as natural capital that supports the capacity to deliver ecosystem services; these in turn provide the benefits we receive as a society. However, the way we manage and change soils means they are subject to threats that result in the degradation of capital, and hence a reduced capacity to deliver ecosystem services. Landscape and planning professionals can work with soil natural capital and ecosystem services to enhance environmental sustainability, climate resilience, and human wellbeing. In this article we offer a short overview of the benefits provided by urban soils, along with some key knowledge gaps.
Ecosystem services frameworks typically identify four main types of service. Underpinning everything are the supporting services, which include a suite of soil processes and functions that drive nutrient cycling, the decomposition and breakdown of organic matter, and water storage or transport. Soil provides a living space for soil organisms, from microbes and invertebrates to larger animals and even birds, and this biodiversity governs many soil processes. These functions in turn support the three classes of ecosystem services that generally receive more attention. These are provisioning services (food or biomass crops, soil as a material or product); regulating services (where soil mediates flows of gases, water, energy, and contaminants); and cultural services (the non-material benefits that people receive from ecosystems, including spiritual enrichment, aesthetic experiences, and recreational activities).
Particularly in urban settings, the function of soils has a huge influence on our quality of life. Any area with growing vegetation, such as grass verges, gardens or parks, will be slowly locking up carbon in the soil. When new areas are sealed by roads, hard surfaces or buildings, even though the disturbance during construction will considerably disrupt and release some of that carbon, the residual carbon remains buried underneath, and can be greater than the carbon in ploughed agricultural fields.
One urban challenge of increasing importance due to climate change is surface flooding. During high-intensity rainfall events, the rate at which water can infiltrate into soils in green spaces helps prevent flooding, and higher organic matter content in soil stores more water. As well as this, soils can play a key role in water filtration and purification as they are a natural filter of pollutants, aiding in the breakdown of chemicals (as in the Heathrow wetlands). How we design and manage our green spaces makes a big difference.
Soil plays a key role in some lesser-known regulating services: for instance, the moisture stored in soil, together with evapotranspiration by trees, helps to cool urban environments. Conversely, when soil moisture is limited, it can intensify heatwaves. Research estimates that interactions between low soil moisture and high air temperature can increase the duration of heatwaves by 50–80%. Soils also help reduce noise levels. Soft ground is excellent at absorbing low sound frequencies, and this is factored into the noise models that calculate how far road and rail noise propagate away from the source.
Soils’ support of cultural services is largely unstudied yet ironically is among the oldest evidence we have of creativity, through the use of ochre and other soil-based pigments by both modern humans and Neanderthals. Soil fauna, such as earthworms and ants, inspire interest in children from an early age. Soil textures and colours shape our cultural context and meaningful relationships with landscapes, for instance the red sandstone soils of the Midlands, or the dark peaty fenland soils in parts of East Anglia.
Although soil science has been studied for at least 150 years, and arguably much longer depending on your definition, many gaps in our knowledge remain. This is particularly the case in cities, where management of soils in green spaces is very different compared to where soils are typically studied in agricultural settings, forestry, or semi-natural habitats.
Does our management of parks for recreation influence their ability to store carbon or the infiltration of flood water? How long does an artificial soil take to become more like a naturally formed soil; will it support the same biodiversity; and how does its function change over time? Can we ‘design’ more multifunctional artificial soils with properties that serve multiple purposes from the outset? Do novel substrates in green walls and green roofs function meaningfully as a soil? These questions are best answered by partnerships between scientists and the citizens, companies, institutions, and authorities that are responsible for much of the land management in cities. Working in partnership can help us to understand the impact of our actions on soil function, and how we might improve the outcomes for all our benefit.
Laurence Jones is Group Leader and Principal Research Scientist with oversight of urban research, David Robinson is a soil specialist and Principal Research Scientist, and Alejandro Dussaillant is an Engineer and Senior Hydrologist at the UK Centre for Ecology & Hydrology.
