The changing landscape and urban heat intensity in Ibadan city; a call for Climate Action

Cities are developing with changing surfaces, increasing structures as well as human socioeconomic activities. Activities associated with industrialization and urbanization, rapidly increasing within cities, have resulted in several environmental problems. Some of these include but are not limited to atmospheric and environmental pollution, increased energy consumption, poor and deteriorating visibility, local and/or regional climate change and urban heat effects. In recent times and across the globe, there has been increasing awareness on the term urban heat and its implication on the environment and public health. Urban heat can be explained as the relative warmth or temperature increase experienced, usually at the city center, compared to surrounding areas. This is usually due to the presence of urban surfaces and structures, intense commercial activities, lack of vegetation, etc., in cities. Urban heat have been reported to have severe implications on public health, causing dehydration, heat stress, other physiological discomfort and even death in extreme cases, particularly in the most vulnerable population. Considering the problem of a changing climate and the accompanying uncertainties in recent times, there has been the need for periodic re-examination of the urban climate of tropical cities in order to have an update and compare the situation in these cities with that of other cities in the world. Ibadan is one of those tropical cities that should be examined within this context.

Ibadan - a rapidly urbanizing city

Ibadan is located south-west of Nigeria, at about 128km inland northeast of Lagos and about 530km southwest of Abuja – the capital city of Nigeria. It is located within latitudes 7o 15’N and 7o 30’N of the equator and longitudes 3o 45’E and 4o 00’E of the Greenwich meridian, and lies completely within the tropical forest zone but close to the boundary between the forest and the derived savanna. The region is a landscape consisting of all land use types ranging from agricultural lands to various urban-related land uses. The metropolis or the core of Ibadan is prominent for industrial and commercial activities in places such as Dugbe. Unlike the city centre, the surrounding areas are notable for basically subsistence pattern of agriculture. Ibadan in Oyo state has undergone several developmental stages and phases till date. Many parts of the region can now be considered as urban centres and feature loads of urban related activities and structures. Urbanization and industrialization that is largely occurring has led to increased population with strong influence on the environment. The natural landscape is being replaced by an agglomeration and clustering of both planned and unplanned building structures, surfaces being paved, deforestation largely occurring, and many more, with enormous adverse effects on the environment. These activities have been observed to result in preferential heating of the city, resulting in increased temperature, compared to surrounding (rural) areas. Because Ibadan city is getting rapidly urbanized, with changes in the landscape, there is the need to address these impacts before they are completely militated by the modern trend of human population explosion, and human and industrial activities. This article therefore provides evidence on the changing landscape and increasing urban heat, as a backdrop for effective climate action to cope with these impacts which may severely affect public health.

The changing landscape of Ibadan city

Within the entire region, the landscape includes built-up areas and structures, high vegetation, light vegetation, water bodies and bare surfaces. The extent of each category has experienced significant changes since 1990s till date. For instance, the built-up areas, concentrated at the center of the region, as at 1990 occupied a lesser percentage. This is no longer the case as there has been a massive expansion in the size of the built-up areas. This definitely means that there are more buildings, structures and commercial activities than in the earlier days. The extent of the built-up area which was about 15.2% of the total land area of the whole of Ibadan in the year 1990 increased to about 33.84% in year 2020. Although this has huge socioeconomic benefits, there are resulting impacts meted on the environment and on the human population. This urban expansion has led to a consequent reduction in vegetated surfaces as well as agricultural land estimated from about 78.82% in 1990 to about 55.44%. A number of forested areas and vegetal cover has been lost to urban surfaces, construction and commercial structures. This replacement of vegetation with impervious urban surfaces has eventually led to an increase in the thermal condition across the region. Temperatures rise with increased urban activities, and therefore lead to intense urban heat within Ibadan.

Rising temperatures and urban heat island effects

Recall that urban heat is the preferential heating of the city center compared to surrounding areas. The city center which experiences this preferential heating in this case is regarded as the urban heat island (UHI). Interestingly, this phenomenon is observed within Ibadan where the city center has been observed over time to be a lot hotter than surrounding areas. In the year 1990, this urban heat island was observed to be of a relatively small size covering majorly the metropolis, with the highest temperatures between 26.50C to 31.70C. Fast forward to date and the size of the UHI has expanded significantly, covering more areas within the region. More importantly, the temperatures have increased significantly, with the highest temperatures between 30.50C – 37.60C. This evidently reveals that there has been continuous increase in temperature over the years, with the size of the urban heat island expanding outwards. It is interesting to note that as the size of the “built-up areas” expands as illustrated earlier, so does the size of the UHI, following the same pattern. In simple terms, as more places are getting urbanized moving outward of the city center, so is urban heat spreading and getting more intense. The Local Government Areas which are covered entirely by the extent of this urban heat include Ibadan North, Ibadan Northeast, Ibadan Northwest, Ibadan Southeast, and Ibadan Southwest. Today, some of the locations within the UHI include Iwo road, Mokola, Dugbe, Gbagi, Iyaganku, Ilupeju, Apete market, Ogbere, Egbeda, etc. These locations experience significantly higher temperatures and this has consequent implications on the living conditions of the vast population.

Conclusion

In a fast-paced world where socioeconomic development is foremost, it is important to consider resulting implications on the wellbeing of the population and environment. Urban heat, if left unchecked is a threat to public health, as much as it is to the environment. As the climate changes, these impacts will be exacerbated, resulting in more complex situations. It is therefore important to make efforts manage the intensity and resulting impacts of urban heat within the region. Moving forward, the rapid rate of urbanization should be minimized, while urban spaces and structures can be complemented with green spaces and vegetal structures in order to mitigate the high temperatures, eventually minimizing the UHI effect within such areas. Afforestation – tree planting – programmes should also be encouraged as this will help to increase vegetation cover and reduce heat intensity. Finally, and more extensively, in the execution of construction projects and other activities within Ibadan, and in-depth impact assessment should be carried out to determine and where necessary limit associated impacts. Limitations to the buildup of urban structures should be set, and all environmental variables put into consideration in the planning process and execution of projects within the region’s landscape.