Urban Heat Island and Its consequential Effects on Urban Populations in Nigeria
Cities are influenced by their environment, because of this, there is a change in the relationship between biological and physical aspects of the environment, day-to-day human activities do make not only urban areas a generator of heat but also inject various solid, liquid, and gaseous pollutants into the city atmosphere. These pollutants encourage the development of greenhouse effects and also form nuclei over the city, which enhances increased precipitation over the city.
Lagos is the most populous city in Nigeria and the second-largest city in Africa after Kinshasa, DRC, having a population of 14.8 million as of 2021 within the city proper. The Lagos metropolitan area has a total population of 21.3 million, making it the second-largest metro area in Africa, after Cairo (New York Times, 2014). Less than a million people lived in Lagos in 1960. By 1990 it reached four million, and around fifteen million by 2015. Estimates are higher at twenty million if the population of the surrounding area is included. As a result of the increase in population in Lagos, it has given rise to expansion and various constructions of buildings; different land covers such as concrete pavements, asphaltic pavements, and interlocking pavement, and other infrastructures the main driver of growth in Lagos over the past 50 years has been rural-urban migration. People are encouraged to leave the countryside by push factors such as the lack of job opportunities and low wages.
Urban heat island effects can be defined as the increase of temperature mostly at night in a metropolitan city such as Lagos compared to its surrounding rural areas. This can be attributed to two significant factors, which are human activities and land use. Temperature Differences between noon and midnight variation of maximum UHI in Lagos is on the rise due to the excess heat retention of the urban form and pollution during the day, which is later released at night. As a result of the dense population in Lagos has given rise to expansion and various constructions of buildings and different land covers such as concrete pavements, asphaltic pavements, interlocking pavement, and other infrastructures. There are different types of activities going on in highly populated areas, such as traffic congestion and industrial manufacturing activities, which generates a high rate of air pollution and heat from vehicles, generator exhaust, and cooling systems, Which in turn Increase the general temperature of the immediate environment within the metropolis, this has been accounted to be the leading cause of urban heat island effects in Lagos.
Noon and midnight variation of maximum UHI in Lagos (Ojeh et. al,2016)
Effects of urban heat island
Urban heat island has a significant effect on the health of people living in the urban areas. Generally, such health hazards include depression, restlessness, heat rashes, and sleeplessness, affecting occupational performance or increasing the risk of hospitalization and even death. According to the world health organization, heat also has essential indirect health effects. Heat conditions can alter human behaviour, the transmission of diseases, health service delivery, air quality, and critical social infrastructures such as energy, transport, and water.
Facts and observations show that increase in population is the leading cause of urban heat island in Lagos. It will be important for other states governors to develop their states, attract investment, and support SMEs, creating employment opportunities. Lagos state government should also take urban planning seriously in the further development of the city and introduce building materials that will increase the albedos (the proportion of the incident light or radiation reflected by a surface) in the living areas. With a low albedo value, characteristics of black asphalt absorb a large percentage of solar heat, creating warmer near-surface temperatures. This can be achieved by using light-coloured concrete, which has a high reflective appearance, and reducing the ambient temperature.