Less than Earth’s 3%terrestrial surface is covered by cities (Schneider et al. 2010) and these cities are often located in regions that are rich in biodiversity. But rapid urbanisation due to growing human population is considered as one of the major causes of declining natural habitats and resources that poses a serious threat for the plants and animal species co-inhabiting with humans. The expansion of cities in size and density (Turrini and Knop 2015) in some developing countries of world (Seto et al. 2012) has contributed in higher rate of urbanization realized in Southeast Asia in particular (Cohen 2006; United Nations Department of Economic and Social Affairs UNDESA 2012). A potential measure to this problem can be achieved by identifying urban green spaces that are to be maintained and conserved. As urban green spaces by its definition are inclusive of all the public and private open spaces, primarily covered by vegetation (Tuzin et al. 2002), it can be an effective interdisciplinary approach towards sustainable development and encompass environmental, economic, social and psychological values. They also act as protected areas for the breeding of various animal species and the conservation of plants, soil and water quality (Haq 2011). Although urban areas are known to have lesser number of native species (Emlen 1974; Rebele 1994) as compared to natural habitats, but urban green spaces house a number of different species and also act as dispersal corridors (Bolger et al. 2001). Besides, quality urban green spaces in higher numbers can also be a refuge habitat for numbers of forest dwelling species (Park and Lee 2000; Mortberg and Wallentinus 2000).
The study of urban green spaces is very limited in Indian context. Only a few literatures are available (Pawe and Saikia 2018; Birkmann et al. 2016) on population aspects and forest cover change in urban cities of India. However, in the global context urban landscapes are being studied for various aspects including conservation importance of green spaces (Bolund and Hunhammar 1999; Baycan and Nijkamp 2004; Tian et al. 2011; Jennings et al. 2016). The nature of urban green spaces has been evaluated by certain criteria viz. their quantity in a particular city (Oguz 2000), their existing qualities like activities and experiences and their benefits as perceived by the users (Herzele and Wiedeman 2003) and their services determined by their location and distribution or accessibility in the whole city (Herzele and Wiedeman 2003; Grahn and Stigsdotter 2003; Neuvonen et al. 2007). Different methodologies have been used to study the urban green spaces and the plant communities within them such as random stratified sampling (Nowak et al. 2008), GBH and NDVI calculation (Nero et al. 2016), Analytic Hierarchy Process (AHP) modeling and use of GIS (Ridder et al. 2004; Sharma et al. 2022) etc.
But due to various anthropogenic causes as a consequence of urban sprawl, these green spaces are at the risk of vast changes and degradation, which will ultimately affect the urban wildlife as well as the human residents themselves. In India, nearly half of the 100 million new urban residents are expected to occupy the secondary or mid-sized cities including the cities of northeast India (Birkmann et al. 2016). Guwahati is one such secondary city which is likely to experience population outbursts in a few decades. Guwahati, like many other Indian cities, faces problems of unplanned LULC change due to negligible or even non-existent planning efforts added by the rapid urban population growth (Pawe and Saikia 2018).
With this background, this study aims to determine the temporal changes in the urban green spaces within the boundary of GMDA and also to detect the changes in three selected green patches between 1972 and 2022 in terms of area with the help of remote sensing (RS) and Geographic Information System (GIS), which shall shed light on the impact of urbanization on urban green spaces. The plant community structure of three selected urban green patches of Guwahati has also been studied to emphasize on the importance of urban green spaces in the conservation of wildlife.