Definition of Brownfield Sites
What is a brownfield site?
Brownfield sites, also known as 'open mosaic habitat', are typically defined as land that has been previously developed, often for industrial or demolition purposes, and subsequently abandoned or left vacant. While the common understanding involves derelict industrial land, the term can also encompass other areas significantly altered by human activity, even if not strictly industrial, where nature has still found a foothold.
Brownfield sites are distinct because they are heavily influenced by human activities and fall further along the spectrum between semi-natural and artificial habitats. Unlike more "natural" areas, their characteristics, particularly soil composition and structure, are a legacy of past human use. This leads to a unique blend of vegetation types and microhabitats not typically found together in other settings.
Yes, absolutely. In some areas, like Sidmouth, 'brownfield' sites aren't restricted to derelict industrial land or vacant demolition sites. They can include areas where human activity has significantly changed the original natural state, such as redundant agricultural land or even places where people work, rest, and play like town centres, parks, gardens, and playing fields. These areas, despite their different origins, can still provide niches for wildlife.
Brownfield sites are crucial for biodiversity because they act as refuges for early-successional species that are often rare or absent in the wider urban landscape. They offer undisturbed bare substrate, allowing primary succession to occur. The varied and often unusual habitat structure, including thin soils, bare ground, rubble, and diverse vegetation types, supports a wide range of species, particularly invertebrates, some of which can be as abundant as in ancient woodland. They provide vital resources like nectar, basking areas, and shelter.
The environment on a brownfield site is highly variable due to its history. Soils are often thin and skeletal, with varying chemical content and pH. The vegetation can range from lichens and mosses on bare ground to tall ruderal herbs like rosebay willowherb and stinging nettle. Brownfield sites can also include pools, short open turf, flower-rich grassland, and scrub. Buildings on these sites can even be colonised by wildlife. Essentially, they can contain a mosaic of vegetation types found in other habitats, but within a unique urban context.
The thin, skeletal soils on brownfield sites are significant because they are crucial for maintaining the habitat in an early-successional stage. This soil structure prevents the dominance of more competitive plant species, allowing the characteristic patchy vegetation and the presence of early-successional plants to thrive.
No, historically, the ecological importance of brownfield sites has not been widely recognised. However, this has changed, and they are now established as an important component of semi-natural sites. 'Open areas mosaic habitat' is now even recognised as a Priority Habitat in the UK.
The primary threat to brownfield sites often comes from planning procedures and the presumption in favour of development, especially if they are not considered of high environmental value. Conservation efforts focus on raising awareness about their ecological value, conducting surveys to document the species they support, ensuring long-term continuity of the habitat, and potentially integrating wildlife interest into redevelopment proposals to minimise the impact on biodiversity.