Urban land: ecosystem services

Natural neighbours

18 August 2017

As more humans move into cities, urban land is creating habitats for animals and living systems that provide important ecosystem services – which should not be taken for granted, writes Jim Harris

More than half of the human population currently lives in urban areas, and that proportion is expected to rise to 2/3 by 2050. The land in such areas is assumed to be urbanised, confined to fragments between roads and buildings and designated areas of leisure activity, and so tends to be regarded as being ecologically uninteresting or unimportant.

But urban land provides habitats that are becoming scarce in rural areas. They can be rich in biodiversity and, most importantly, help urban dwellers by providing “ecosystem services”: the benefits that humans receive for free from other systems.

These include the fundamental role of green spaces, or “green infrastructure”, in improving quality of life by supporting physical and psychological health through access to the natural world.

Ecosystem services also play a less well-understood role in waste disposal, in preventing erosion and in the regulation of water, soil nutrients and carbon. The concentration of urban populations means that more people depend on these kinds of benefits, and to a greater extent, than in rural areas.

As societies, we cannot take urban ecosystem services for granted

As societies, we cannot take urban ecosystem services for granted. It is important to understand, instead, how we can reduce the demands that intense urban development make on the wider environment.

That means making the most of all the interactions between urban living and the natural world, looking at how the different forms and designs of urban areas affect those relationships, and finding ways to maximise the benefits provided by ecosystem services.

Urban studies

Cranfield University has been leading a 6-year research project for the Biodiversity & Ecosystem Service Sustainability programme, funded by the Natural Environment Research Council, among a team of postdoctoral and PhD researchers from the University of Sheffield, the University of Exeter and the British Trust for Ornithology.

The project integrates work in the disciplines of soil science, botany, ornithology, mapping and social sciences. The main location for study is the so-called Cranfield Triangle, which includes the urban areas of Luton, Bedford and Milton Keynes. These have been chosen as they represent 3 different types of urban space; specifically, the industrial development of Luton, the medieval roots of Bedford and the modern planned space of Milton Keynes.

Emerging evidence from studies has included the ways in which natural areas improve mental, physical and social health in urban environments:

  • scavengers play an important role in the ecosystems of urban areas;
  • biodiverse urban meadow plantings benefit both people and wildlife; and
  • different types of urban form determine the movement of garden birds, and therefore also the flow of cultural services that they provide.

By using full waveform aerial laser scanning, researchers have been able to measure and model the structures of urban vegetation in 3 dimensions, providing a basis for understanding its actual extent and the interactions in that environment.

Free waste disposal

Scavenging, the act of consuming dead animals, is important for the ecosystem cycle, its structure, functioning and stability. The fact that there are fewer predators in urban areas means that there is more potential for animal carcasses to be left in populated urban streets.

Around 3/4 of animal carcass mass is removed by scavengers such as crows, magpies and foxes – which are some of the least well-liked, sometimes persecuted species

One project study looked at quantifying the role of vertebrate scavengers – that is, birds and mammals rather than insects – in urban environments in 3 towns in the UK. It was found that around 3/4 of animal carcass mass is removed by scavengers such as crows, magpies and foxes – which are some of the least well-liked, sometimes persecuted species.

Meadow power

Large green spaces in urban areas tend to be kept in pristine condition, managed as parks with formal pathways, borders and beds for shrubs and flowers. Such an approach requires a large-scale, ongoing investment of resources.

Another study has looked at the value of wild meadows as an alternative: 10 urban meadows were created and responses gathered from visitors, and the more informal, wilder landscapes were preferred, with a greater preference still for meadows that offered more variety in terms of plant species and plants of taller height.

As might be expected, there was less enthusiasm for meadows among those people with a greater attachment to the original site and its use, but, crucially, the visitors were tolerant of the way the meadows looked outside the flowering season – especially when they were given information on the cost savings and biodiversity advantages these provided.

This offers an example of how the relationships between people and their environment can be improved at the same time as improving ecosystem services.

Bird feeding

We looked at a specific example of interactions and the tradition of bird feeding. It is a popular activity – but why? Households were surveyed for their motivations.

The study found that people who did so regularly felt more relaxed and connected to nature when they watched garden birds, and thought that feeding was beneficial for bird welfare. Feeding birds was found to be an attempt to create a connection with the natural world.

Effects on practice

Findings are to be used to help inform strategic decisions in town planning and legislation that relates to the preservation and use of green space in the UK and, internationally, efforts to mitigate climate change and protect and expand species.

Evidence is being provided to policymakers and legislators. Lessons learned are also being applied on the Cranfield Campus, with new planting of seed mixes to encourage biodiversity.

It is envisioned that town planners will use these findings to help decisions such as to how to make investment in green spaces, in terms of where, what type and how extensive.

There are clear benefits for all ecosystem services; these may be most easily realised in the development of new urban extensions, but could also inform the enhancement of green features in existing areas. Tools for evaluating green spaces and connectivity are already available, and dissemination of these through presentations and on the project website is being planned.

More work is required to determine in detail the effects of urban green spaces, and the interaction and interdependencies with the other components of urban form and function – in other words, the grey–green–blue infrastructure of the system as a whole.

Jim Harris is Professor of Environmental Technology at the Cranfield Institute for Resilient Futures

Further information