Natural wonder: Biodiversity strategies in action
Urban areas can provide homes for many species and plants that bring a multitude of benefits to the population. Dr Richard Delahay and Mark Line, explain why companies should strive to contribute to a richer environment by enhancing the biodiversity
Biodiversity. The word typically conjures up images of tropical rainforests or coral reefs. But of course the term refers to the richness of all the world’s living organisms and ecosystems,wherever they are found – from mountain tops to rocky coasts, in prairies, deserts, the open oceans and even in our semi-natural agricultural landscapes.
But biodiversity in cities? Surely not? Well, think again. Your typical urban environment may have relatively few ecological features and be dominated by hard landscapes with limited and highly structured planting. But cities are by no means bereft of biodiversity. And while green spaces play a key role in bringing components of the natural world into the urban environment, the biodiversity of a city is influenced by much more than its parks.
Biodiversity can crop up in far less obvious places, if you know where to look. Derelict urban areas previously associated with industrial use – now unflatteringly known as ‘brownfield’ sites – can be ecologically exciting places, home to specialised plant communities and invertebrates which are rarely found elsewhere.
And if that is not exciting or glamorous enough, then how about an urban resident that is an iconic flagship species of UK wildlife conservation? Peregrine falcons (which are afforded the highest degree of legal protection under Schedule 1 of the Wildlife and Countryside Act 1981) find feral pigeons an abundant food source, reason enough to take up home on the precipitous ledges and crevices of high rise buildings in the midst of some of our largest cities. These include London, Cardiff, Birmingham and Manchester, where the towering manmade structures echo the mountainous crags and sea cliffs of the peregrine’s natural habitat. And the Peregrine falcon is not an isolated example. Urban areas can provide unique niches for many species, particularly those whose natural habitats are mimicked by features of the built environment. For instance, the sheltered cavities and crevices of complex urban structures provide many opportunities for roosting bats.
In the UK, part of the historic city of Bath is designated as a Special Area of Conservation (SAC) because of important roost sites for greater horseshoe and Bechstein’s bats. A study in and around Chicago suggests that urban areas may in fact provide islands of favourable habitat for some species, amidst a wider landscape dominated by low value, intensive agriculture.
The potential for finding plants and animals of conservation value in urban environments raises issues for urban planners and developers. It is a misconception that no ecological value is lost when developing brownfield and built sites. Indeed, the threat to biodiversity of an urban development can far exceed that of building on poor agricultural grasslands that typify, for example, much of the UK’s greenbelt. In the UK we have a framework of legislation relating to the conservation of wildlife and habitats, and the protection of biodiversity is of material consideration in planning applications. Developers may be required to carry out ecological monitoring, assess the potential impact and implement mitigation measures.
Recent advances in our understanding of the potential biodiversity value of urban sites have seen planning authorities question the wisdom of an automatic preference for development on urban brownfield sites. And a potential reprieve for such sites of urban biodiversity may be an unplanned consequence of the UK Government’s 2011 Budget Plan for Growth, which has removed previously developed land targets for housing.
But while protection of individual sites is one thing, the potential for enhancing the biodiversity value of urban environments by developing landscape scale strategies is also being championed by some wildlife charities and community groups. In the UK the importance of urban ecosystems is recognised by the Wildlife Trust’s Living Landscapes initiatives which include the development of a network of wildlife-rich green spaces throughout the historic industrial heartlands of the West Midlands known as the Black Country. In the US a project in San Francisco aims to create corridors of habitat to join up fragmented remnant populations of the green hairstreak butterfly.
A common theme running through these urban biodiversity initiatives is the need to develop connectivity amongst ecosystems, both within the built environment and with surrounding areas. As Annie Coombs, fellow of the Landscape Institute, says: "Small oases of open space in urban areas are important for many reasons, wildlife being one of them. But far greater value to wildlife is achieved when these spaces form part of a connected network, allowing passage of wildlife, seed dispersal and potentially other functions. Taking a green infrastructure approach to planning and managing open spaces enables multiple, compatible benefits to be delivered. It is important to consider this at a landscape scale and not to be constrained by e.g. local authority boundaries".
Urban green infrastructure
Joining up urban green infrastructure in this way not only maximises the benefits to wildlife but it also has a significant impact on the human population. An area of intense research interest amongst ecologists is the relationship between biodiversity and ecosystem services. Ecosystem services are the benefits to humanity that flow from functioning ecosystems – examples are products like food and other raw materials, and processes like the pollination of crops and CO2 sequestration.
Traditionally, the flow of such services has been from the countryside into the cities to support the appetite of our urban population, in the process consuming our natural capital and the benefits that flow from it. For this reason the ecologist Charles Odum once described cities as "parasites in the biosphere".
But the ecological systems in urban environments do produce beneficial ecosystem services. Cities’ green infrastructures – all types of green spaces, soft landscaping, street trees and other plantings – help by improving air quality, regulating temperature and humidity, reducing noise and surface water run-off, and providing recreational opportunities and increased aesthetic appeal. Alongside improving residents’ quality of life, they can also have economic benefits, and there is evidence that they may enhance our physical and mental well-being.
It is even conceivable that urban biodiversity may export ecosystem services to the wider environment. Researchers at Bristol University have embarked on a study to assess the importance of flowering plants in urban areas in sustaining pollinating insects, raising the possibility that the built environment may be instrumental in restoring their populations for the benefit of agricultural systems elsewhere.
The extent and potential benefits of green infrastructure vary from city to city. Recent research suggests that environmental performance declines with increasing density of buildings and people, but there is scope for improvement. Initiatives to conserve and manage existing sites are one method, but another is to develop niches and ecosystems in urban environments. Space is often at a premium in the built environment so adding substrates and vegetation to roofs has provided a popular approach in recent decades. In addition to providing environmental benefits such as reducing the energy consumption of buildings and storm-water runoff, these ‘green roofs’ can also be valuable habitats for animals and plants. Similarly, niches for wildlife can be created by incorporating bat and bird boxes into the design of new buildings.
Ecologists tasked with mitigating the ecological impact of developments increasingly advocate the construction of roof-top habitats and wildlife-friendly features. However, such approaches require careful consideration and appropriate advice is needed to address the substantial challenge of ensuring that such enhancements are appropriate to the local ecology and hence maximise biodiversity gains and ecological performance. Often we look to the corporate sector for the resources to fund innovation and action on pressing sustainability problems. Those companies that are directly involved in building design and construction are naturally responsive to regulatory drivers and planning requirements focused on wildlife conservation. But more generally, even the most engaged companies remain confused by the concept of biodiversity and what that means for their business. This means that there are relatively weak drivers for change coming from the private sector itself.
From a policy perspective, the more active businesses focus on their relationship with priority species and habitats – which generally directs their attention away from the urban environment, towards their landholdings in more rural settings. There are some notable exceptions, but there remains an opportunity for those companies wishing to demonstrate continuing leadership for their sustainable business practices, to explore how they can contribute to a richer urban environment.
Change will only come through the specification of features that support a more diverse variety of species and communities at the design stage – and there are relatively few examples of best practice beyond green roofs and soft landscaping. For companies looking to act responsibly, there is no common approach to assessment of biodiversity across the principal sustainability tools. Although the Building Research Establishment Environmental Assessment Method (BREEAM) and Leadership in Energy and Environmental Design (LEED) do allow credits for some ecologically focussed features, they remain a weak incentive and unfortunately interpretation of their requirements can encourage a short-termist, check list approach. But they are at least a start.
Over half of the world’s population now lives in cities. It is widely held that the detachment from the natural environment that has accompanied the process of urbanisation has alienated us from nature.
For many people urban green infrastructure may provide the only everyday opportunity to experience elements of the natural world. Perhaps enhancing biodiversity in urban environments can help to reconnect urbanites with nature’s capital and the benefits that flow from it.
This can only help in raising awareness of the wider importance of global biodiversity to human well-being and to reawaken our sense that we are all part of the natural world. And so are our cities.
Dr Richard Delahay is a senior ecologist at Biocensus and Mark Line is executive chairman at Two Tomorrows