Any site that has been altered by human activity can be considered ‘brownfield’. This not only includes derelict areas in towns and cities but quarries, brick-pits, old railway lines and disused airfields. Farmland and forestry plantations are not generally considered to be brownfield sites.
To find out more about Buglife's work to conserve brownfield wildlife sites click here.
Why are Brownfield sites so important for invertebrates?
Brownfield sites have as many associated Red Data and Nationally Scarce invertebrate species as do ancient woodlands. While not all brownfield sites have value to invertebrates, many contain significant reservoirs of biodiversity.
|Typical brownfield site © Greg Hitchcock|
On the most wildlife-rich brownfield sites the cycles of disturbance and abandonment combine with a low nutrient content to favour the development of a wide variety of habitats, plant species and hydrology. Many invertebrate species have a complex life-cycle, with different requirements at different stages, so often require two or more differing habitats in close proximity.
The existence of these habitat mosaics is essential to the survival of many species, while the habitats themselves may be an important resource because they may be rare in the wider agricultural countryside, as is the case with flower-rich grasslands.
Many flying insects require a foraging area where nectar and pollen may be gathered. The size and nature of the foraging area needed differs from one species to another, as some forage on many different flowers, while others are more choosy. The low nutrient content of many brownfield sites results in higher plant diversity as fast growing species are unable to dominate. The thin, dry soils also result in drought-stressed plants, which put more effort into flowering increasing the nectar and pollen resource further.
The invertebrates that are attracted by the plants and habitats attract other invertebrates themselves. Open flower-rich vegetation, grassland and scrub all provide different opportunities for different predators.
Open bare areas are an important and often undervalued resource, offering a number of benefits. Bare ground warms up rapidly in sunshine, is used by burrowing and ground nesting invertebrates and provides a foraging area for visual predators. Artificial substrates or disturbance through unofficial use make brownfield sites important reservoirs for bare-ground species.
Plant-eating invertebrates often live inside leaves, stems, flower heads or seeds and overwinter in these places, under logs or stones, or in ground litter. For these species it is critical that their over wintering sites persist from one generation to the next, and it is the lack of management of grasslands on brownfield sites that contribute to their value for these invertebrates.
Brownfield sites provide ‘surrogate’ habitats for species that would be associated with other habitats were it not for man’s influence on his environment. The intensification of farming has led to the loss of flower-rich grasslands from the countryside, leaving brownfield sites as the last refuge for species reliant upon such resources. The now-scarce Brown-banded carder bee (Bombus humilis) and Shrill carder bee (Bombus sylvarum) have important population centres on brownfield sites in the Thames Gateway, as such sites replace the Thames Terrace grassland habitats that have been largely lost to development. The stabilisation of cliffs and creation of flood defences has left many bare-gound species with nowhere to go but brownfields.
|A flower-rich inner-city brownfield site © Greg Hitchcock|
To reduce urban sprawl, government policy adopts a ‘brownfield first’ approach, targeting new developments onto available sites within the urban area. While this is a good idea in principle, it does not take into account biodiversity. Planning Policy Statement 9 should allow for the protection of biodiversity, even on brownfield sites, but attitudes to brownfield sites do not reflect their value to wildlife, and they are often seen as ‘useless’. Public perception of brownfield sites – as areas of antisocial behaviour such as fly-tipping and drug-abuse – do not help in efforts to conserve them, yet for many of these sites there is no reason why they cannot provide a valuable open space for the local community. Conversely, the ‘pretty’ greenspaces that surround towns and cities that have strong protection from development (both through the planning process and through public opinion) are often part of the legacy of this country's recent agricultural history, and have little value for wildlife.
Mismanagement by well meaning conservationists or local authorities can also be a threat. Turning a brownfield into ‘pretty’ greenspace through importation of topsoil, seeding of grassland and planting of trees, or ‘greenwashing’ as it is known, can be as devastating to brownfield wildlife as development.
Buglife are working to address the issue of brownfield biodiviersity through our ‘All of a Buzz...’ projects. Through developing a strategy for the conservation of our most important brownfields, we hope to change public opinion on the value of the sites and encourage a ‘biodiversity first’ approach to planning, where sites of low-biodiversity, whether brownfield or greenfield, are prioritised for development.
New developments on brownfield sites should incorporate areas of brownfield habitat and wildlife-friendly designs such as brown roofs and green walls.