Soil Security in the City: Why Urban Soils Matter More Than Ever

Every year on December 5th, World Soil Day invites us to pause and appreciate something we often take for granted: soil. It is the living skin of the Earth, supporting our food systems, regulating water and climate, cycling nutrients, storing carbon, and sustaining biodiversity.

This year’s theme, “Healthy Soils for Healthy Cities”, encourages us to shift our attention from rural landscapes to the ground beneath our urban environments.

Most people imagine soil as something found in fields, forests, and farmland. But soil does not disappear in cities. It lies beneath our streets, buildings, parks, and gardens. With more than half of the global population living in urban areas, and that figure rising, urban soil has never been more important. If soil is essential to life, then it is essential to urban life as well.

What Soil Security Means for Cities

The concept of Soil Security provides a framework to protect soil’s ability to function now and into the future. Built around five key dimensions (capacity, condition, capital, connectivity, and codification) it helps us understand how soil supports both ecosystems and societies. Originally applied to agricultural landscapes, this framework is just as important for urban soil management.

Even when hidden beneath pavement, urban soils play vital roles in making cities livable. They support urban trees and green spaces that reduce heat, filter stormwater, regulate local climates, store carbon, and provide habitat for a rich community of soil organisms.

They also create places that support mental well-being and community life. In many ways, urban soils quietly sustain everyday urban resilience.

Yet these soils are also among the most threatened. Soil contamination from industry, traffic, and waste can leave behind heavy metals and pollutants. Soil sealing, which occurs when soil is covered with asphalt or concrete, stops soil function entirely. Soil compaction from construction restricts air, water, and root movement. In many cities, soil is treated as a surface to build on, rather than a living ecosystem that needs protection.

The Diversity of Urban Soils

Urban soils are incredibly diverse because they are shaped by a mix of natural processes and human activities. To make sense of this variety, soil scientists use a few helpful categories.

Phenosoils are urban soils that people have created or reshaped for a purpose. These include soils in parks, gardens, sports fields, and landscaped areas. They often contain added materials such as compost, sand, or gravel to help them drain well, support roots, or look good. In other words, they are designed to do a specific job.

Genosoils are different. These are naturally formed soils that have managed to survive even as cities grew around them. They hold valuable clues about the original landscape and can help us understand what the soil in that area used to be like. They are important reference points when we want to compare how much other urban soils have changed.

Securing Soil in Urban Landscapes

Applying the Soil Security framework to cities helps identify what soils are capable of, how they are functioning today, how they contribute to community well-being, how they connect with wider ecological and social systems, and what policies exist to protect them.

Understanding soil capacity means exploring whether urban soils can support vegetation, manage water, and sustain microbial life. Assessing soil condition involves examining compaction, contamination, structure, and biological health. Considering soil capital means recognising the ecological and economic value soils provide, from carbon storage and climate regulation to recreational and cultural benefits. Connectivity highlights how soil interacts with stormwater networks, biodiversity corridors, urban trees, and human behaviour. Codification underscores the need for strong policies, urban planning regulations, and soil protection standards to prevent degradation and sealing.

Urban soil assessment is complex. Reference soils may be missing, and data may be incomplete. Yet understanding these soils is essential.

We cannot manage what we do not measure, and we cannot secure what we do not value.

A Shared Responsibility

Securing urban soils is both a scientific challenge and a social one. People relate to soil differently depending on where they encounter it. In gardens, it is nurtured. In parks, it is appreciated. On roadside verges or vacant lots, it is often overlooked. Increasing soil literacy through school programs, community gardens, citizen science, and composting initiatives can help people reconnect with the soil beneath their feet.

Governments and planners have a crucial role as well. When cities recognise soil as essential urban infrastructure, meaningful change becomes possible. Planning codes can limit soil sealing, encourage soil restoration, promote topsoil reuse, and integrate soil considerations into nature-based urban solutions.

Healthy soils create healthy cities. Protecting these soils strengthens community well-being, climate resilience, and environmental sustainability.

Conclusion: Secure Soils, Secure Cities

As cities continue to expand, the importance of urban soil security becomes even more critical. Soil security is not an optional add-on to sustainability planning. It is central to building resilient, healthy, and livable urban environments. Protecting urban soils means valuing them, understanding their condition, preventing contamination and sealing, involving communities in their stewardship, and embedding soil considerations into every level of urban planning and policy.

On this World Soil Day, we have an opportunity to extend our appreciation for soil into the heart of our cities. The soils beneath our streets, gardens, and parks may be quiet, but they are indispensable. By securing them, we secure the future of our cities and the well-being of generations to come.

And don’t miss our two new videos: one explaining how we can work together to secure urban soils, and another offering a more artistic, engaging look at the hidden life beneath our cities. We hope you enjoy them!

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