Brownfield sites are the gaps in urban areas where factories once stood. They cover a significant, if scattered, amount of land in the old industrial areas of East and South East London, stretching far into Essex and Kent along the Thames estuary. Bordered by housing estates and industrial parks, these sites have in some cases been neglected and unused since as far back as the Second World War.
To the disinterested eye they are spare ground, home to nothing but weeds, rubble, burnt-out cars and dumped appliances, and an obvious place to build new homes in a region where housing is so scarce essential workers cannot afford to buy a home.
This policy has long been seen as an environmentally sound way of dealing with the housing crisis. Green belts, areas of countryside surrounding the UK's major cities, were created in the 1950s to stop the spread of urban sprawl, and the government is reluctant to build on them. Filling in the gaps left by defunct industry in urban areas seems like the obvious answer to the problem.
However, naturalists have increasingly noted that brownfield sites not only provide a haven for wildlife, but are amongst the most important ecological sites in England. Furthermore, hard against built-up areas and open for public access, these sites are a valuable resource for England's majority urban population.
England has a unique ecology. It isn't just chance that has made it a nation of gardeners - the mild climate, changeable weather and sharply defined seasons make for a high diversity of plantlife. The Thames estuary suffers poor soil, upping the competition between its flora, the result being an even higher biodiversity. And where there is biodiversity in plantlife, there is also biodiversity in animals.
A recent article in the Guardian highlighted an example of this, a brownfield area of Canvey Island in Essex. Not only home to rare plants and animals, this rubble-strewn piece of land, between a petrochemical works and a built-up area of London's endless suburbs, is also home to unique flora and fauna found no-where else in the world. It is earmarked to be built on as part of the government's new housing policy.
I have spent a lot of time wandering on sites like these - where I live in south east London, miles away from the countryside, they offer me an opportunity to indulge my interest in wild flowers and wildlife I otherwise wouldn't have. Rare stag beetles, rare mosses, emperor dragonflies, orchids and meadow flowers can be found on wasteland walking distance from my home. Significantly, I would be hard pushed to find these in the countryside itself.
In the green belt around London industrial crop farming has created a monoculture more barren for wildlife than the city itself. Made up largely of private land closed to the public, and saturated in pesticides, these EU-subsidised farms cover a disproportionate area of a crowded region.
The housing crisis poses difficult questions for the government, and it is obvious that homes must be built somewhere. Building on the green belt would raise anger in a public unaware of industrial farming's detrimental effect on wildlife, bring the Labour party into further conflict with the Conservative rural areas, and could raise problematic issues of compulsory purchase. Brownfield land is cheap, unsightly, and viewed as unimportant by the public. But in building on it, we could lose some of the last bits of wild England we have left.