Environmental Effects
The phenomenon of Urban heat islands has become a growing concern. Incidence of this phenomenon as well as concern about it has increased over the years. An urban heat island is formed when industrial and urban areas are developed resulting in greater production and retention of heat. A large proportion of solar energy that affects rural areas is consumed evaporating water from vegetation and soil. In cities, where there is less vegetation and exposed soil, the majority of the sun’s energy is absorbed by urban structures and asphalt. Hence, during warm daylight hours, less evaporative cooling in cities results in higher surface temperatures than in rural areas. Vehicles and factories release additional city heat, as do industrial and domestic heating and cooling units. As a result, cities are often 2 to 10 °F (1 to 6 °C) warmer than surrounding landscapes. Impacts also include reducing soil moisture and a reduction in re-uptake of carbon dioxide emissions.
In his book Whole Earth Discipline, Stewart Brand argues that the effects of urbanisation are primarily positive for the environment. Firstly, the birth rate of new urban dwellers falls immediately to replacement rate, and keeps falling, reducing the risk of environmental stresses caused by population growth. Secondly, migration away from rural areas may reduce the prevalence of destructive subsistence farming techniques, such as improperly implemented slash and burn agriculture..
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