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Brown can also be green

Government housing targets for 2008 require 60 per cent of new homes to be built on brownfield sites in order to protect the countryside and Green Belt from urban sprawl. But brownfield sites can be richer in biodiversity and wildlife than much of the countryside. By Peter Wilder and Sue James

Biodiversity is the 'variety of life', the myriad plant and animal species (including humans) and the range of habitats in which they live. At the 1992 Earth Summit at Rio de Janeiro, 150 national governments attended a biodiversity convention. In the UK the result has been the development of strategies and action plans at national, regional and local level. The new biodiversity agenda takes nature conservation beyond the protection and management of special sites by emphasising the opportunities for action throughout the environment.

The planning paradox

Current planning policy prioritises the development of 'brownfield' land, which is often seen as an opportunity to clear the site and start again. Yet survey evidence shows that previously developed urban wastelands can be particularly rich in wildlife and biodiversity - indeed more so than the official countryside, which has been much damaged by modern farming methods and poor environmental management.

A recent report by the London Wildlife Trust, Brownfield? Greenfield? The Threat to London's Unofficial Countryside (2002), suggests that 'they are technically green fields but they are often sterile areas for people and wildlife. Similarly our Green Belt land, strongly protected against development by planning policy, is often inappropriately managed and of low wildlife, landscape and recreational value.'

Brownfield sites, conversely, provide the potential for open space in urban areas where it is most needed, a fact that is recognised by PPG 17, which explicitly requires local authorities to 'seek opportunities to create public open space from vacant land and to incorporate open space within new development on previously used land'.

Some brownfield sites, such as car parks or existing empty buildings of no significant architectural or historical interest, have little wildlife or amenity value and would be the first choice for redevelopment. Others, such as the Sites of Metropolitan Importance in London, which 'contain particularly rare species, rare assemblages of species or important populations of species' are the highest priority for protection.Yet, according to the London Wildlife Trust, seven of these sites have recently been lost to development.

Wastelands also remind us of the historic diversity of our urban existence.Unused land around ports, for example, has often been colonised by plants and animals that have come in with trading ships. Former heavy industrial sites can be valuable amenities.

The decommissioned Thyssen steel works in the Ruhr valley is a case in point. Since it would have been uneconomic to dismantle and clean up the site, it was turned into a heritage site and leisure attraction, with recreational activities such as rock climbing and an emerging forest community rich with wildlife, butterflies and birds.

A matter of pedigree PPG 3 gives a definition for 'previously developed land' and also provides an important exclusion from development: 'Land that was previously developed, but where the remains of any structure or activity have blended into the landscape in the process of time (to the extent that it can reasonably be considered as part of the natural surroundings) and where there is a clear reason that could outweigh the reuse of the site - such as the contribution to nature conservation - or it has been subsequently put to an amenity use and cannot be regarded as requiring development.'

One problem here, which has been identified by the London Wildlife Trust, is that many urban wastelands are at an earlier stage of colonisation and so do not meet the conventional idea of 'blending in'. Indeed, they are often viewed as unsightly.

In Cities and Natural Processes (1995), Michael Hough challenges our perceptions when he talks of two urban landscapes: the formalistic and the natural. The former is the 'nurtured 'pedigree' landscapes of mown turf, flowerbeds, trees, fountains and planned places, which have been the focus of civic design - its survival dependent on high energy inputs, engineering and horticultural technology' and, of course, limited in terms of biodiversity. The other is 'the fortuitous landscape of naturalised urban plants providing shade and flowering ground covers and wildlife habitats at no cost or care and against all the odds', in polluted atmospheres and often contaminated soils. The 'pedigreed' landscape has a place but, contends Hough, it should not represent the 'universal' city landscape.

We may need to adjust our expectations and perceptions of landscape in our cities, just as we did when we abandoned our preference for carefully controlled parterres in favour of Lancelot Brown's expansive parklands.

It should be possible to develop brownfield sites that are rich in biodiversity into a network of protected urban nature reserves, open spaces and green corridors, providing a transition between hard landscapes, formal landscapes and naturally regenerated landscapes. Equally, it is essential that we use Countryside Stewardship schemes to encourage farmers to improve the biodiversity and wildlife value of Green Belts and 'official' countryside. Our urban regeneration policies only make sense if we have a countryside that is worth protecting.

Peter Wilder is an associate at Lovejoy London.

Sue James is an architect in private practice

The Thames Gateway, the largest redevelopment of brownfield land to date, presents many environmental challenges and offers an opportunity to put the highest standards of sustainability, ecology and biodiversity into practice. The Farrell/Lovejoy/Symonds proposal for the London Olympic bid proposed the removal of traditionally engineered flood defences in the Lea Valley in favour of environmentally diverse flood buffer corridors.

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