Urban green areas have developed over several centuries to become an essential component of modern town and city planning. These green areas provide many social and ecological services such as helping to improve climate, hygiene, aesthetics, recreational opportunities, environmental protection and biodiversity. Urban green areas also help to create important ecological networks. From a landscape ecology point of view, urban and rural ecological networks may provide the only opportunity for corridors, connectivity and wildlife movement throughout fragmented landscapes.
Maria Ignatieva (Swedish University of Agricultural Sciences), Glen H. Stewart (Lincoln University) and Colin Meurk (Landcare Research) have reveiewed the evolution of urban ecological network concepts, analysed the evidence for network functionality, and examined innovative ways of achieving opportunities for the enhancement of biodiversity and ecosystem services. This article summarises their findings and discusses the many benefits of green spaces in cities.
Early examples of urban green areas have been described by Ignatieva, Stewart and Meurk as explicitly visual and intuitively ecological improvements. From the sixteenth to eighteenth centuries, the benefits associated with urban green areas were aesthetic. As urban areas became increasingly industrialised, the beautification of cities provided a somewhat fortuitous design for what have become urban ecological networks.
During the Industrial Revolution nature was often swept aside. Woods and commons sometimes became enclosed by urban sprawl, later becoming formalised public green areas, such as the Gunnersbury Triangle Nature Reserve in London. In a matter of preserving what remained, the remnants of indigenous forests have often been incorporated into the green infrastructure of many cities and towns , such as the oak woods of Moscow’s Bontanical Gardens, London’s Hampstead Heath or Christchurch’s Riccarton bush.
The democratisation of western society during the nineteenth century resulted in public green areas becoming a crucial part of urban planning. Urban settlements became shaped according to new regulations and planning codes that were aimed at providing livable conditions for their citizens. Thus began the era of modern cities.
The era of modern cities brought about the greenbelt concept and the Garden City movement. Garden Cities included rings of green open spaces, carefully arranged green areas and recreation facilities as core considerations as they strived to achieve a new generation of urban settlements and healthy citizens. Planned green areas and the connectivity of urban, rural and natural landscapes were a particularly positive outcome of the Garden City movement.
The worlds first Garden City was Letchworth, England, founded in 1903 by Ebenezer Howard. Since then, one of the largest cities inspired by the Garden City movement is the Australian capital, Canberra. Canberra is often referred to as the “bush capital”, due to so many green areas being incorporated into its urban environment. Many cities have adopted the greenbelt idea, and today these comprise core areas for ecological networks and corridors for nature within an urban environment.
Over the last few decades there has been an awakened ecological understanding that organisms might be able to use these greenbelts and other green urban spaces as a form of “green highway”. This seemingly logical idea was termed the ecological corridor concept, although its functionality has been hard to prove.
A significant contribution to the development of urban ecological networks has been the greenway movement in the USA and Canada and the green corridor movement of some European countries in the 1990’s. By 1995 there were more than 500 greenways in the USA, linking rural and urban areas and providing access to open space. An example of the USA’s greenway movement can be found in Seattle, where a programme aims to design an integrated and connected green infrastructure. Greenways, greenbelts and green spaces help to provide a comprehensive green infrastructure and are important for the development of urban ecological networks.
The urban green practices of Europe and the USA have influenced Southern Hemisphere countries, such as New Zealand. In New Zealand, the debate about functionality, connectivity and the value of attracting certain biota is very contentious. Enhancements to the physical and spatial environment can have a paradoxical effect and be detrimental to indigenous biodiversity.
A major problem for the conservation and management of New Zealand’s indigenous biodiversity has been caused by the loss of lowland forests and the introduction of exotic plants and animals. These introduced species are generally more competitive in nonforest conditions, making it hard to determine what role networks and corridors might play.
Recent evidence for wildlife movement along green corridors can be equally applied to indigenous species and exotic pest species. However, most mobile species can easily utilise the stepping stones provided by urban green areas. As long as some of these stepping stones are large enough to support breeding populations, then it is possible for urban ecological networks to create interacting indigenous metapopulations. A metapopulation is group of populations that are separated by space, but consist of the same species. By linking these populations together via green corridors, genetic bottlenecks (sharp reduction of a population and its genetic diversity) and local extinctions may be avoided. Private gardens can also provide important stepping stones in urban ecological networks, helping to enhance indigenous biodiversity by connecting different habitats.
The planning and design of urban ecological networks in the twenty-first century is seen as a multidisciplinary approach involving various potential ecological areas throughout cities. Remnants of original indigenous vegetation are prioritised in these networks as unique sources of indigenous biodiversity. Planted urban woodlands, golf courses, cemeteries, waterways, wetlands, motorways, railways, public parks and gardens are a focus for urban planner’s and landscape architect’s work towards urban ecological networks and green infrastructures.
This multidisciplinary approach to the planning and design of ecological networks in contemporary cities requires integration between ecologists, landscape architects, urban planners, politicians and indigenous representatives. New models of urban ecological networks should respect, conserve and enhance natural processes. Internationally innovative planning and design approaches should be researched and implemented, helping to create a new generation of urban ecological networks that are not only aesthetically pleasing, but also providing health benefits and act as green corridors for indigenous biodiversity.
The author Shyam Provost is a postgraduate student at Lincoln University. He wrote this article as part of his assessment for ECOL 608 Research Methods in Ecology.
This blog entry has been based on the following peer reviewed journal article:
Ignatieva, M., Stewart, G. H., & Meurk, C. (2011). Planning and design of ecological networks in urban areas. Landscape and ecological engineering,7(1), 17-25.