Quantifying the ecosystem services provided by urban green spaces

A new study has quantified the ecosystem services (ES) provided by green spaces in Rotterdam, the Netherlands, using new methods to evaluate high-resolution land-cover data.

The findings show that different types of green space provide different ecosystem services, highlighting the importance of careful design during city planning. The authors say their method to map ecosystem services supply will aid the design of healthy, climate-resilient cities.

Urban green spaces, which include parks and playing fields, have important benefits. They provide a range of ecosystem services and can help to mitigate problems that are particularly prevalent in cities, such as air and noise pollution.

Despite their importance in urban areas, most studies of ES focus on rural or natural landscapes. This may be because existing methods to quantify ES struggle to cope with the high-resolution land-cover data necessary to assess ES in a city context.

To improve understanding of urban ecosystem services, this study derived new methods to quantify and map such services supplied by urban green spaces. The methods, based on land-cover data and a literature review, were applied to Rotterdam. The second largest city in the Netherlands, Rotterdam faces challenges common to many European cities, including heat stress, flooding and air pollution.

The researchers, supported by the European Commission via projects TURAS1 and OPERAs2 , selected six urban ecosystem services: air purification (defined as the lowering of background air pollution concentrations), carbon storage (gross above ground carbon storage), noise reduction (the capacity of vegetation to attenuate environmental noise), run-off retention (the combined effect of rainfall interception, infiltration and storage), cooling (temperature reduction by vegetation) and recreation (the potential of green spaces for everyday outdoor recreation). These were chosen due to their relevance for human well-being.

To determine the spatial distribution of each ecosystem service, the researchers mapped them onto the city landscape using data on the locations of eight different types of urban green space (trees, woodland, tall shrubs, short shrubs, herbaceous, garden, water, and others, such as allotment gardens and sports fields). This data was compiled from a combination of green maintenance maps, cadastral maps and land-use maps.

Indicators for each ES were obtained from a literature review and applied to the green space data within the geographic information services platform ArcGIS 10.1.

The researchers calculated the ecosystem services supplied by each individual green space and at the neighbourhood and district levels. For each urban green space they multiplied the area by the ES supply rate per square metre. The ES supplied by individual green spaces was then aggregated to the neighbourhood and district levels.

Analysis showed that different green spaces have different capacities for ecosystem services delivery. The spatial arrangements of green spaces are also a key determinant of ecosystem services supply. For example, trees can be more effective in filtering pollutants from the air when they are close to the source of pollution.

Differences in the availability of green spaces can lead to significant spatial variation in ES supply across a city. In general, supply increases with distance from the city centre.

The researchers say this is because central neighbourhoods tend to be more developed and are therefore less green. In Rotterdam, there were clear spatial discrepancies in ecosystem services supply; some districts completely lacked green spaces and therefore received low levels of ecosystem services, while others received high levels of numerous or even all such services.

This study shows that not only the amount but also the composition and arrangement of urban green spaces influence the type and level of ecosystem services provided to neighbourhoods.

The methodology used here to map ES shows which services are supplied, where, in what quantity and by which green spaces. The authors say this approach will help urban planners to ensure that the ecosystem services needs of neighbourhoods are met, and ultimately to design more sustainable cities.

Source: Derkzen, M., van Teeffelen, A. & Verburg, P. (2015). Quantifying urban ecosystem services based on high-resolution data of urban green space: an assessment for Rotterdam, the Netherlands. J Appl Ecol, 52(4), pp.1020-1032. DOI: 10.1111/1365- 2664.12469 – “Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by SCU, The University of the West of England, Bristol. 8 October 2015 Issue 430