The population of urban areas, particularly in developing countries like ours, is growing at fast rate due to continuous immigration from the countryside in search of better employment opportunities. The continuous increase in population of the cities and towns has led to the alteration of natural land surfaces into the anthropogenic land-use/land-cover (LU/LC) types for the expansion of industrial, commercial and residential colonies.
Urbanization led LU/LC changes comprises the transformation of pervious vegetated surface as well as other natural surfaces into the impervious built-up surfaces. One of the major consequences of this transformation of pervious surfaces into the impervious built-up surfaces is the changing pattern of the urban climatic system which is apparently indicated by the increasing surface and air temperature which in turn affects the thermodynamics of urban surface. As a result, the heat gets accumulated for longer periods in the land surface which in turn leads to increased land surface temperature (LST) in the urban areas further leading to the development of urban heat island (UHI) phenomenon. Therefore, the urban areas always have a higher LST than their surrounding countryside because the density of built-up surfaces is always higher in the cities and towns.
India is witnessing rapid urbanization during past few decades, especially after the Economic reforms of 1991. The metropolitan cities of India such as Mumbai, Delhi, Kolkata and several others have noticed high rate of urbanization after 1990 which has resulted in significant increase in the urban heat island intensity in these cities.
The vegetation density controls the surface and near surface temperature and put diminishing effects on the urban heat island. Various studies show that large area of the vegetation cover has been replaced by the built-up surfaces and other LU/LC types in our cities – mainly due to increasing needs of housing and transportation network. The problem will only intensify in the coming years as the migration of people from non-urban areas into urban areas is only going to increase in the coming years.
Therefore, there is an urgent need to incorporate the green and open spaces in various parts of our cities. Our city master plans have always been mobility and realty centric and have seldom paid any attention to development of green spaces nor made new provisions for such spaces. This has to change and increasing green cover (such as public open spaces and community parks) should be given enough importance in our plans. This will not only help in urban heat island mitigation but also will lead to better urban ecosystem and promote the physical activities among the urban dwellers.