New methodology to assess the state of urban ecosystems

Irene Vega

Urban ecosystems provide multiple goods and services that have a direct impact on human health, such as air purification, noise reduction or temperature reduction. Both the quantity and quality of these goods and services generated depend on the condition (state and/or quality) of the ecosystem itself. However, there are a limited number of studies that assess this condition at a local scale.

A research team from the Rey Juan Carlos University (URJC), in collaboration with the company Ecoacsa Biodiversity Reserve SL, has developed a methodology to evaluate the condition of urban ecosystems, specifically in the city of Madrid. This work has been based on the guidelines of the Economic and Environmental Accounting System (SEEA – EA), promoted by the United Nations, which provides a standardized methodology to assess natural capital. “The objective of our study has been to develop a methodology that offers advantages compared to other existing metrics and that can be used as a basis, for example, for the Green Infrastructure and Biodiversity Plan or the General Urban Development Plan of Madrid,” highlights Adrián García Bruzón, researcher in the area of ​​Environmental Technologies at the URJC and co-author of the study.

The results obtained, recently published in the scientific journal Ecological Indicators, show in detail the condition of the urban ecosystem that forms the city of Madrid. In addition, having calculated the condition of each polygon into which the city is divided, allows us to identify priority areas for action, both those that, due to their poor condition, require urgent improvement interventions and those that, due to their good condition, require conservation actions.

The study reveals that the areas with the best condition are located in the northwest of Madrid, close to the reference polygon of El Monte de El Pardo, since they are located far from the sources of pollution and are those that generate more ecosystem services. On the contrary, the areas that show lower condition values ​​are those in the city centre, where there is greater atmospheric and acoustic pollution, there are water and thermal problems and the provision of ecosystem services they generate is lower.

“It is also very important to know which variables we need to modify minimally in order to quickly change areas with poor condition into areas with good condition. For example, an action aimed at connecting urban parks and other green areas may have a greater influence on improving the condition of Madrid than establishing plans to reduce CO2 or SO2,” says García Bruzón.

Satellite images to identify and classify spaces

Satellite images were used to carry out the study, applying remote sensing techniques and geographic information systems. First, the physical space of Madrid was classified into urban categories (urban parks, communication routes, forests, etc.) and the variables that influence the condition of this city were selected based on bibliography and previous experiences. Next, the reference area (the one with the highest condition) was identified and the similarity between the reference area and the other areas was analysed. Finally, a single condition index was generated with a range between 0 and 1.

The average condition of the neighbourhoods included in Madrid was calculated from this index. 23,66% of the neighbourhoods were in good condition (condition index greater than 0,60) and 76,34% of the neighbourhoods were in poor condition (condition index less than or equal to 0,60), resulting in an average condition for the city of Madrid of 0,69. “The condition index can be used to evaluate the effectiveness of urban policies over a period of time. An increase in the index would suggest the success of the policies applied, while a decrease would indicate the need to reorient these policies and carry out urgent interventions,” concludes the URJC researcher.

This index could also serve as a basis for the Green Infrastructure and Biodiversity Plan or the Madrid Strategic Plan. In addition, cities could use this methodology as a tool to analyse their resilience to climate change, project their future trends or identify inequalities in the distribution of natural resources.

Image: Spatial representation (at pixel level) of the urban condition index of the city of Madrid (top left) and the average of the urban condition index for each neighborhood in Madrid (top right). The images below represent three enlarged areas so that the detail of the calculated condition index can be appreciated.