Soil Matters: Integrating Soil into the Planning Practice

Soil matters: integrating soil into the Planning Practice

by Yoann Clouet

In the last decade, soil, its functions and the beneficial ecosystem services it can provide, have been getting more and more interest for their potential in the development of sustainable cities. But for decades the soil resource has been under the significant pressure of urbanisation and is now heavily impacted by the consequences of climate change, with direct changes to its physical, chemical, and biological properties. In the early 80s already (FAO & ITPS, 2015), the Food and Agriculture Organization of the United Nations (FAO) adopted the World Soil Charter (FAO, 1981) and United Nations Environment Programme (UNEP) published the World Soils Policy (UNEP, 1982), recognising the importance of soils for sustainable development, calling for policies and practices that mitigate soil erosion, pollution, and loss of fertility. The principles and definitions provided useful guidance for national governments to help them design policy and pursue actions on sustainable soil management, and increased awareness on soil benefits. Yet, concrete strategies to enhance soil health and quality in the urban environment remain limited. This paper presents in further details the main benefits that can be derived from soil, why soil inclusive spatial planning is important, and the current state of the planning practice on the topic.

THE BENEFITS OF SOIL FOR URBAN DEVELOPMENTS: SOIL FUNCTIONS AND RELATED ECOSYSTEM SERVICES FOR SUSTAINABLE CITIES

In the past 40 years, the planning practice has slowly veered from focusing on urban functions and urban features to acknowledging the role of environmental performances in the urban environment, and their integration in planning. Soil is specifically crucial for urban development as it offers numerous benefits and functions (soil performances). The FAO describes eleven soil functions (FAO, 2015):

However, in order to provide soil performances, the soil resource must be healthy (soil quality) and sufficient (soil quantity). Urban development and climate change negatively impact soil properties as they contribute directly or indirectly to the following pressures (Maes, 2016):

SOIL SEALING: soil is covered by impermeable surfaces such as roads, buildings, and parking lots.

SOIL COMPACTION: soil particles are pressed together, reducing pore space, air circulation, and water infiltration.

SOIL CONTAMINATION: pollutants such as heavy metals, chemicals, and waste released into the soil can accumulate over time, making the soil toxic for plants, animals, and humans.

SOIL EROSION AND LAND-SLIDES: soil, especially topsoil, exposed to wind and water erosion because of loss of vegetation coverage is more vulnerable to being washed-away and cut-and-fill activities can weaken soil structure, leading to more frequent landslides.

LOSS OF ORGANIC MATTER: reduced green spaces, vegetation cut-offs and lack of aeration (due to compaction) limit inputs of organic matter from plant litter feeding the soil, while higher temperatures speed up the decomposition of organic matter, causing it to be broken down faster than it can be replenished.

SOIL SALINITY: build up of salt due to improper drainage, rising sea levels and in increase droughts that affects soil chemical properties.

SOIL ACIDIFICATION: more acid rainfall due to industrial activities and fertilisers lower the soil pH.

LOSS IN BIODIVERSITY: urban development leads to the fragmentation of green space and shifting climate zones result in biodiversity loss.

Considering the impact of urban activities and climate change on soil properties, it is therefore essential for urban planning to consider this finite resource. Urban planning needs to take account of the relationship between the different soil properties and their role into urban socio-ecological system in order to propose planning strategies that maintain or optimize soil health and its related ecosystem services, and contribute to mitigate or adapt to the pressures it faces.

SOIL IN THE CURRENT PLANNING PRACTICE

A number of policies emerged in the last few decades championing soil health, but despite growing recognition of the importance of soil health, in the 2015 the FAO noted that the actual adoption of sustainable soil management practices remains limited (FAO & ITPS, 2015). In 2017, the United Nations Convention to Combat Desertification (UNCCD), identified in its Global Land Outlook (2017) a disconnect between policies aimed at land and soil restoration and their practical execution in land-use planning and management. It noted that many sustainable practices remain inadequately implemented due to lack of incentives, awareness, and integration into broader land management strategies.

Furthermore, a majority of them focus on agricultural land and agricultural practices, and disregard the specific of the pressures faced by the soil resource in the urban environment. A few examples are nevertheless to be noted:

In the US, the Green Infrastructure Policy initially adopted in 2000 and its subsequent updates promotes the use of green infrastructure in urban planning to manage stormwater, reduce erosion, and increase soil permeability.

In the UK, the National Planning Policy Framework (NPPF) introduced in 2012 and its subsequent updates promotes sustainable development in urban areas and includes provisions for protecting and enhancing soil resources (reuse of previously developed land (brownfields) and limiting soil sealing) and encourages local planning authorities to prioritize soil conservation in urban planning.

In the European Union, a Research and Innovation mission, titled “A Soil Deal for Europe”, was launched in 2021. It focuses on achieving healthy soils in Europe by 2030 and seeks to combat soil degradation, erosion, and contamination and specifically looks into the development of soil inclusive planning and supports research on soil health in the urban context.

From the urban planning perspective, recent research suggests that, although soil is recognised as a key resource, urban planning still fails to integrate indicators to measure or monitor soil-related functions (Teixeira da Silva et al., 2018).

From the one hand, urban planning needs to become more engaged with soils, but soil science should also ensure data and knowledge on soil performance in the urban environment is well understood. This means adapting and making use of tools and methods for soil assessment to understand and monitor soil-related ecosystem services. From the other hand, urban planners need to develop planning strategies and concepts that integrate soil and its functions. Minimal practical guidelines exist on the topic*, yet they remain fragmented or insufficient, focusing often on either soil quantity, quality or performances separately.

It is high time that planners develop soil inclusive urban planning approaches to ensure the regeneration of the urban soil resource and promote its functions to ensure it continues to provide its key ecosystem services for sustainable cities. This can only happen with sufficient guidance and the adequate policy framework.

*Interestingly, a lot of it comes from the Netherlands.

Photos by Tom Misk (left) and Pok Rie (right) | Pexels

References

FAO and ITPS, Status of the World’s Soil Resources (Chapter 8 Governance and policy responses to soil change); 2015, p.225. Accessible online: https://openknowledge.fao.org/server/api/core/bitstreams/7ad71507-1b95-433f-a781-c0833295a4d9/content

FAO, World Soil Charter; 1981.

FAO, Soil Infographics, Global Soil Partnership; 2015. Accessible online: https://www.fao.org/global-soil-partnership/resources/news/presentations-gsb23/en/c/284443/

Maes J., Mapping and Assessment of Ecosystems and their Services (MAES): Highlights and uncertainties of a science-policy interface on biodiversity and ecosystem services, Ekonomia i Środowisko; Fundacja Ekonomistów Środowiska i Zasobów Naturalnych; 2016. pp. 52-64. Accessible online: https://publications.jrc.ec.europa.eu/repository/handle/JRC103434

Teixeira da Silva, R., Fleskens, L., van Delden, H. et al., Incorporating soil ecosystem services into urban planning: status, challenges and opportunities, Landscape Ecol 33, pp: 1087–1102 (2018). Accessible online: https://doi.org/10.1007/s10980-018-0652-x

UNEP, World Soil Policy; 1982.

FAO, World Soil Charter; 1981.

FAO, Soil Infographics, Global Soil Partnership; 2015. Accessible online: https://www.fao.org/global-soil-partnership/resources/news/presentations-gsb23/en/c/284443/

UNEP, World Soil Policy; 1982.

ISOCARP Institute

ISOCARP Institute