Assessing ecological risks of urban air and water environment to analyse the scenarios for mainstreaming nature-based solutions: A case study of Bengaluru City, India

Urban ecological risks are intricately linked to several environmental and anthropogenic factors which need closer attention to these relationships at local scales. Among factors enhancing the impacts of urbanisation, land use changes and land management frameworks, the management of the urban air quality as well as the availability of blue-green infrastructure to alleviate these risks are not well connected with each other despite their synergistic effects over the environmental and public health of urban centres as reported by several studies. Hence, quantification of the ecological risks as well as derivation of nature-based solutions as effective strategies facilitating the urban sustainability needs to be examined in detail at different spatio-temporal scales to derive the appropriate strategies and policy formulations to decrease the risks. The present study takes the case of Bengaluru city to assess and quantify the ward-wise and overall ecological risks associated with the reduction in green cover, conversion of permeable land into concreted surface as well as the increase in particulate matter in the air. Differential scenarios with respect to the combination of three factors, ratios of the extents of green-to-blue areas, percentage impervious surface area and air quality index, were studied to identify those causing summative reduction in the ecological risks for the city. The use of nature-based solutions in managing the risks is examined from the perspective of mainstreaming them in land management practices for urban areas such as the Bengaluru urban area.