A Study Of Urban Land Cover Changes In Nigeria Based On Multi-Temporal Satellite Data

The world has continuously witnessed tremendous urbanization and changes in global land use/land cover(LULC)patterns due to rapid urban population growth.The global population of urban dwellers has substantially increased over past decades and is expected to increase further,with a greater proportion of this growth concentrated in countries of Asia and Africa.These two continents,i.e.,Asia and Africa,are having the fastest urbanization than any other continent.Africa,the least urbanized continent,presently has the highest rate of urbanization in the world.The consequences of this urbanization have contributed to numerous environmental and socio-economic problems.Therefore,sustainable urban development is increasingly becoming a widely discussed topic in several disciplines such as urban studies,environmental sciences,engineering,and many others.The concept of sustainable urban development is crucial to reducing the adverse impact of urbanization through a responsible approach.In 2015,the United Nations proposed 17 sustainable development goals,of which the 11 th is to create inclusive,safe,resilient,and sustainable cities.Therefore,the effective monitoring of urban growth and change dynamics of landuses helps achieve this Sustainable Development Goal.Recent studies have focused on urbanization and land-use changes in different geographical regions such as Asia,Europe,and America.However,little spatial information is available to vast researchers,particularly in China,regarding Africa’s urbanization and changes in land use.The scarcity of this data serves as a great obstacle to quantifying urbanization and achieving sustainable urban development in such regions.The availability of remotely sensed data and Geographical Information Systems(GIS)helps play a vital role in overcoming these challenges in Africa,particularly Nigeria,which has inadequate land use information of its major cities.Against this backdrop,the research employed multitemporal satellite data to achieve sustainable and resilient cities in Africa’s most populous nation,i.e.,Nigeria.The utilization of such data provided a faster,effective,and more reliable approach to monitoring LULC in Nigeria than the traditional methods requiring field surveys.Landsat satellite images were used to map and retrieve spatial data of four major cities,while Geospatial techniques were used to analyze land-use transitions,urban growth and predict future changes in land uses for proper planning and mitigation of various environmental challenges such as urban flooding due to inadequate urban infrastructures and LULC data.The study further examined the influence of urbanization and change dynamics of land use on urban microclimate using land spectral indices that include the Normalized Difference Vegetation Index(NDVI)and Normalized Difference Built-up Index(NDBI).For the mapping and monitoring of LULC transitions,the Maximum Likelihood Algorithm(MLA)of the supervised classification method was utilized in generating the land use/land cover maps of four major urban areas/cities in Nigeria.The land uses were classified using Arc GIS 10.7.1 software into four major categories,and the accuracy of the maps was validated using indices derived from confusion matrixes.The results indicated an excellent and reliable classification in all the classified land uses with an overall accuracy above 80%and a Kappa coefficient higher than 0.75.The generated LULC maps were then employed into the Land Change Modeler(LCM)of IDRISI-Terr Set geospatial software to detect the various changes in land-uses.The study further analyzed the changes using PostClassification Comparison(PCC).The outcome revealed significant transitions with numerous losses and gains in the different land use/land cover patterns of the four cities/study areas under consideration.These findings established the historical trend and provided the scientific basis for modeling future land uses and planning for sustainable development.The research spatially mapped urban growth and employed an annual growth rate indicator to analyze the expansion of built-up areas due to the tremendous growth of Nigeria’s urban population since its independence in 1960.Urban areas such as Lagos have witnessed rapid growth,with the development of the city indicating three phases of urban expansion.The results showed that the city’s built-up area increased substantially from approximately 496 sq.km in 1990 to approximately 1256 sq.km in 2020,indicating an annual urban expansion of 25.33 sq.km over the last three decades.The re-occurring urban flooding in Lagos is attributed to the city’s unsustainable growth,which results in inadequate urban infrastructures to service the growing urban population.Such infrastructures include roads,drainages,sewers,and waste collection and handling facilities.Therefore,urban development has contributed substantially to the environmental problem of urban flooding in Lagos.The non-availability of the forecasted land use/land cover data of urban areas such as Zaria and Lagos also serves as a great hindrance to the proper physical planning of these cities.Hence,the study further employed an integrated CA-Markov model that combines the advantages of the cellular automata and Markov’s model’s contiguity to forecast urban growth and future changes in land-uses of these two cities,i.e.,Zaria and Lagos.The simulation models were validated using the Kappa statistical parameters to determine their ability to identify spatial location accurately.Based on the model’s success,the calibrated CA-Markov models were then used to predict the change dynamics of future land-uses based on the transition probability matrix.The result shows that Nigeria’s urban expansion will continue over the next 30 years,with major cities such as Lagos having declining vegetation cover,barren land,and water bodies.Such findings will significantly help in planning and the management of urban growth.The research further retrieved Land Surface Temperature(LST)and spectral indices comprising the Normalized Difference Vegetation Index(NDVI)and Normalized Difference Built-up Index(NDBI)to determine the impact of LULC changes on urban micro climate.A linear regression analysis was then employed to examine the relationship between the different variables.The results indicated a negative correlation between LST and NDVI and a positive correlation between LST and NDBI.Areas with a low vegetation index and high built-up area index experienced greater land surface temperatures.Therefore,land surface temperature as an essential component of urban climate is greatly influenced by the change dynamics of land-uses.The findings provide useful data to researchers and policymakers in optimizing land use and mitigating the adverse impact of urban heat land through sustainable urban development.The study proposed sustainable and heat-resilient strategies to minimize the increasing surface temperature in similar rapidly growing cities around the world.Generally,the research explored urbanization from a global perspective but was limited to monitoring the change dynamics of land uses on a country scale due to time constrain.The findings of this thesis have provided the crucial scientific data needed by vast researchers,particularly those in China,regarding the dynamics of urbanization and landuse change in the most populous country of Africa,i.e.,Nigeria.However,future studies should consider socio-economic development,government policies,and other biophysical and human factors as some of the unprecedented features that may influence the alteration of Nigeria’s urban land uses.