Vegetation changes and formation of small-scale urban heat islands in three populated districts of Kerala State,India

Currently, more than half of the world’s population is living in cities. Rapid and unplanned urbanization became a common scenario in rapidly developing countries such as those in Asia. Decline in vegetation coverage and increase in local air and land surface temperatures are among the adverse effects of unplanned urban growth. We used Landsat data for the period 1991–2017 to estimate the expansion of urban areas in terms of vegetation loss and the development of small-scale urban heat islands in developing cities in Kerala state of India. For the last 27 years, unplanned urbanization in Kerala state has increased and this resulted in the enhanced loss of vegetation and, possibly, resulted in the increase in land surface temperature (LST). Our results indicate that vegetation coverage, particularly near the urban areas, has been decreased by 5.8%, 10.4%, and 9.6% in Ernakulam, Trichur, and Kozhikode districts, respectively. The land surface temperatures also have been increased during the study period. It is interesting to note that higher increase in LST and higher reduction in vegetation coverage were observed in Trichur and Kozhikode districts compared with highly populated and urbanized Ernakulam district.