Developing an integrated urban ecological efficiency framework for spatial ecological planning: A case on a tropical mega metropolitan area of the global south

Rapid urbanization has emerged as one of the most critical challenges to ecological sustainability in urban areas. In developing countries, the degradation of the ecosystem is more prominent due to the lack of urban planning. Thus, it has become urgent for researchers to identify the ecological efficiency (EE) changes imposed by urban expansion and promote sustainable land use planning. This study aims to develop a comprehensive urban ecological efficiency (UEE) framework in the Kolkata Metropolitan Area (KMA), India, from 2000 to 2020. Principal component analysis (PCA) was used to develop a remote sensing-based UEE index (UEEI) based on five effective ecological parameters (Greenness, Dryness, Heat, Wetness and vegetation health. A single sensitivity parameter was also calculated to determine the role of a single parameter based on which management strategies can be carried out. The findings showed that (i) there were substantial deteriorations of UEE in the last 20 years. In 2000 the areas with good EE were about 65.5% which declined to 53.72% in 2010 and 20.87% in 2020. The areas with good UEE decreased 68% and 61% from 2000 to 2020 and 2010 to 2020, respectively; (ii) the areas with good UEE were 52% in 2000, while 38% in 2010. Most urban centres (Bhadreshwar, Champdani, Srirampur, Bally, Howrah, Kamarhati, Baranagar, Dum Dum, South Dum Dum, Rajarhat, Bidhannagar) located around the Kolkata megacity are characterized by poor and very poor EE (ranges of 0.60–1.00). Thus, spatiotemporal pattern of UEE could assist to clarify the administrative responsibilities as well as obligations. In addition to this, the UEE framework can help for scientific guidance of urban ecosystem protection and restoration through comprehensive spatial landscape planning.