Fragments, functions and flows - the scaling of biodiversity and ecosystem services in urban ecosystems

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Urban areas cover just 2.8% of the Earth's land area, but over 50% of the human population lives in them, and these proportions are growing rapidly. Such heavy concentration of people has a wide variety of important consequences. Those for their relations with the environment have attracted much recent attention from the media, pressure groups, policy makers, researchers, and local and national government. Of particular concern have been how improvements can most effectively be made to the environmental conditions experienced in urban areas, to the levels of interaction between urban dwellers and the natural environment, and to the contribution of urban areas to the broader scale provision of ecosystem services. This raises the key issue of the form of relationships between biodiversity and ecosystem services in urban areas, how the structure of urban areas (the spatial structure of the different kinds and extents of impermeable and permeable surfaces; urban form) influences these relationships, and thus how the existing structure can best be managed and how future structure can be planned to best effect.Although understanding of the levels and distributions both of biodiversity and of ecosystem services in urban areas has improved dramatically in recent years the relationships between biodiversity and ecosystem services have been extremely poorly studied in urban areas (and are largely absent from major collations of empirical studies). Indeed, these environments pose significant and unusual challenges:- the urban landscape is highly fragmented, with large portions sealed by buildings and paving;- greenspaces are embedded in a complex mosaic of buildings and roads that imposes major constraints and directionality on the flows of biodiversity and ecosystem service delivery across the urban landscape;- the intensity of human management of these environments can give rise to spatial patterns and scales of flows of energy, materials and biodiversity on which ecosystem services depend that would not naturally occur; and,- the very aggregations of people that give rise to urban areas typically necessitate less conventional approaches to conducting ecological research therein, involving greater engagement with the general public, and less dependence on the use of large pieces of equipment, which is "out of bounds" to the general population.In order to determine these biodiversity-ecosystem service relationships, develop deeper understanding and to test this understanding our overall approach to this project involves five main steps. We shall:- characterise the spatial ecological structure of urban areas;- determine biodiversity-ecosystem service relationships and the influence of connectivity on them;- determine the flows of biodiversity, and service delivery in selected cases;- experimentally perturb those flows to determine the impact on ecosystem service delivery; and- integrate these findings in the form of spatially explicit models which will form the basis of an "ecosystem service" layer for GIS models.This will enable us to deepen understanding, and to provide illustrations for stakeholders (such as planners, local people and NGOs) as to how "scenarios" of different development proposals might be tested, to provide support for decisions based on sound science and stakeholder engagement.