Urban soil is often overlooked as a resource

When you think of soil, you probably think of rolling farmland. But what about urban soil? City dwellers must be responsible for 68% of the world’s population by 2050this often forgotten resource is gaining importance.

Urban farming is gaining popularity. However, urban soil is more often associated with pollution and risk health. But the soil in our parks, gardens and roadsides actually underpins many aspects of our daily lives. As our recent research article It highlights that urban soil provides habitat for wildlife, stores water, provides food, helps fight the climate crisis and improves well-being.

In other words, soil provides many ecosystem services: the benefits we derive from it from the environment.

Soil is more than just an inert material. In Fresh York’s Central Park in 2014, researchers were surprised to find breadth of microbial diversity in the soil was similar to what is found around the world, including in Arctic, tropical and desert soils. Fewer than 17% of the 167,000 types of microbes they identified in the park had ever been discovered before.

Urban gardens can also be biodiversity hotspots. People tend to plant lots of different things or leave the soil alone, allowing soil biodiversity to flourish.

Soil is the largest layer of land coal storage on the planet, storing almost twice as much carbon as all living plants and the atmosphere totalUrban soil does this too, preventing large amounts of coal released into the atmosphere in the form of CO₂.

The soil also stores water, which helps prevent local flooding in built-up areas. Increasingly, cities are installing what are known as Sustainable Drainage Systems (SuDS)such as ditches and rain gardens. These are areas of vegetation with shallow depressions or depressions that can trap excess rainwater, allowing it to slowly soak into the soil and preventing overloading of drainage infrastructure.

For example, in East London Derbyshire Street Pocket Park saw a fenced-off cul-de-sac of a residential street (which was mainly used for illegal dumping) transformed into a bike path and common space with permeable pavement, planters and trees. Crucially, the road and pavement were partially dug up and replaced with turf and flower beds.

And then, of course, there are the nutrients that the soil provides for trees and plants that are crucial in cities. Urban heat islands, which lead to higher air temperatures in cities than in the surrounding rural areas, can be reduced by vegetation.

Trees and plants also absorb air pollutants and improve air quality in the cityand to prove the social and aesthetic benefits of green areas for improving health and well-being. But city trees often fails to survive due to soil compaction or insufficient soil volume. It follows that if we want to reap the benefits of trees, we must first think about the soil.

Treated like dirt

The problem is that we don’t. Urban soil is often treated badly. In construction projects, the reuse of materials must be carefully planned to avoid soil being considered waste. In 2016, soil was an incredibly 55% of materials end up in landfill in UK.

Soil that is not designated for landfill may be removed and collected elsewhere until it is needed – sometimes for years. This deprives it of oxygen and kills the organisms that inhabit it. If soil is left on a building site, it is often heavily compacted. Here, the soil structure – the arrangement of soil particles and the pore spaces within it – is damaged, which in turn restricts the movement of air, water and roots.

Cities are under pressure to expand. As modern homes, roads and urban developments are built, more and more land is sealed with impermeable surfacespreventing the soil from achieving its many benefits.

On top of all this, she also came to last increase in replacing garden lawns with plastic turf. This threatens the rapid degradation of soils in urban gardens and the many ecosystem services they provide.

What can we do?

Urban soil must be considered in city planning and design. On construction sites, it urgently needs to be repurposed as a useful resource and properly managed to avoid landfill.

The construction of the Queen Elizabeth Olympic Park in London required extensive work clean up to tidy up soil contaminated (including oil, gasoline, tar, and ponderous metals) from decades of industrial operate. Soil hospitals were built on-site to perform soil washing (to remove the smallest particles to which contaminants had adhered) and bioremediation (in which microbes are used to break down organic contaminants). More than 80% of the soil was then reused to create modern parkland.

Meanwhile in Fresh York Clean Soil Bank Project sends excavated soil to other construction sites where it is needed, preventing it from being stored in landfills.

This type of intervention tends to only occur on immense construction sites. But if you have a garden, there are many things you can do to aid your soil.

Increasing organic matter adding compost or mulch helps improve soil structure and water capacity, provides better plant nutrition and helps store carbon. Allowing grass to grow longer and planting perennials (and trees and shrubs(if you have the space) will allow for more extensive root growth, which will add carbon to the soil. Finally, avoid over-ploughing or turning the soil as this speeds up the decomposition of organic matter and releases CO₂ into the atmosphere. If you have to get rid of excess soil, try to re-market it locally to people who might need it, rather than throwing it in landfill.

These may seem like miniature changes. But with 87% of UK households having a garden and respect 300,000 people By digging in allotment gardens, we can significantly improve the quality of the soil on which our cities are built.