"Urban Heat Island Effects; A De-Greening Process, Implication for Environmental Sustainability and Quality of Urban Life. A Review"

Urban Heat Island is formed as a result of the degreening of natural vegetative surfaces, due to the development and expansion of an area into artificial impervious surfaces leading to an increase in the ambient and surface urban temperature of the city more than the adjoining rural areas. Urban surfaces are replaced by impervious surfaces such as roads, buildings, and paved surfaces while the rural surfaces are defined by the porous vegetative cover. Temperature differentials between urban and rural adjoining areas are high in urban areas due to high reflectivity and emissivity (high albedo) of urban surfaces. The impacts on humans and the environment are manifold e.g., heat stress, heat cramp, dehydration, low productivity and comfort of ambient city dwellers, reduction in vegetative cover, high evaporation, and evapotranspiration in plants and reduction in soil and water quality of urban areas.