Dynamics of Land Use Land Cover Change in Enugu City of Enugu State, Nigeria

As far as urban expansion is concerned, there is no city in the world that is static. One of the effects of this expansion is vegetation loss and its attendant ecosystem disequilibrium. The aim of this paper is to analyze urban expansion and loss of vegetation cover in Enugu city in Enugu State. Land use and land cover (LULC) in Enugu city has undergone constant change over the past few decades due to major changes caused by anthropogenic and natural factors and the impacts of their activities on the environment and climate of the city. This study used techniques of Remote Sensing and GIS to identify the rate of urban expansion and the degree of vegetal loss using the Landsat imageries of 1989, 1999, 2009 and 2019. The maximum likelihood classication algorithm in IdrisiSelva software was used to extract three major land cover classes i.e. Built up, Vegetation and Non-vegetation. The average rates of change were elicited for each of the land cover types. Vegetation had diminished from 430.75km 2 (77.26%) in 1989 to 313.18km 2 (56.17%) in 2019. Conversely, built-up areas had increased from 67.28 km 2 (12.07%) in 1989 to 170.71km 2 (30.62%) in 2019. Non-vegetation increased from 59.53km 2 (10.68%) in 1989 to 73.67km 2 (13.31%) in 2019. Results also revealed changes in temperature with respect to vegetation changes. The temperature has increased from average of 27 o C in 1989 to average of 29.1 o C in 2019. This has led to an increase of about 2.1 o C. Therefore, the State Development of Environments and other relevant agencies should as a matter of urgency, start working with planners to establish urban greenery as mitigating measure against vegetation loss, environmental and climate change.


Introduction
The multi-directional spreading out of a city and its fringes toward non-built-up areas can be termed urban expansion. Urbanization is the process that refers to the growth both in size and numbers of urban centers. This accelerated growth has been monumental from the beginning of the 20th century (Ifatimehin and Musa, 2006), especially in developing countries such as Nigeria. It is predicated on anthropogenic activities amongst other factors. Increase in population over time, results in sprawling development that consequently manifest in form of socio-economic, health and environmental challenges. These drawbacks also re ect in the poor physical planning of Enugu city as an integral part of a state. The negligence of urban planners to properly situate peri-urbanization landscape during land use planning decisions at various levels, can accentuate future unsustainable land use changes (Grimm et al., 2008).
While land use refers to the way in which land has been used by humans and their habitat, usually with an emphasis on the functional role of land for economic activities, land cover simply means all biophysical characteristics of earth's surface e.g. vegetation, water and other physical characteristics of the land. LULC dynamics are widespread, accelerating, and signi cant processes majorly impelled by human actions and at the same time resulting to changes that impact human livelihood. LULC change is a major issue of concern with regards to change in the global environment (Qian, et al.,2007). Rapid growth and expansion of urban centers, increasing population growth, increasing scarcity of land, increasing demand for industrial products, technological advancements are among the drivers of LULCC in our society today.
The environmental implications of rapidly growing urban areas are unquanti able, they partly manifest by consistent displacement of agricultural land and vegetal loss in the peripheral areas of cities by residential and manufacturing layouts (Martellozo et al., 2014). Looking at urban expansion from global perspective. It was revealed that in the year 2000, urban built-up area in the world consumed about 400,000 square kilometers, which amounted to about 0.3% of the total land area of the world. The research projected that by 2030, about 1,100,000 (about 0.85%) shall be urbanized if the same growth rate is maintained (Angel et al., 2005).
Land use affects land cover and changes in land cover affect land use. A change in either, however, is not necessarily the product of the other. Changes in land cover by land use do not necessarily imply degradation of the land (Fabiyi 2006 andDami et al., 2011). However, many shifting land use patterns driven by a variety of social causes result in land cover changes that affect biodiversity, water and radiation budgets, trace gas emissions and other processes that come together to affect climate and bio-sphere (Kasim, 2012).
This work is premised on Hoyt Homer's Sector Model based on the assumption that common low-income households are usually found near railroad lines, and commercial establishments. In 1939, Hoyt modi ed the concentric zone model to account for major transportation routes.
He postulated that most major cities evolved around the nexus of several important transport facilities such as roads railroads, sea ports, and trolley lines that emanated from the city's center. Hoyt theorized that cities would tend to grow in wedge-shaped patterns, or sectors, emanating from the Central Business District (CBD) and centered on major transportation routes (Hoyt, 1939). Deforestation rate or loss of vegetation in Nigeria is about 3.5 percent which implies a loss of 350,000-400,000 hectares per annum. Between 1990 and 2005 alone, Nigeria lost 21% of her forests (Ladipo, 2010). The indicators of these changes can be clearly seen in the current major global concerns such as increasing concentrations of carbon dioxide (CO 2 ) in the atmosphere, loss of biological diversity, conversion and fragmentation of natural vegetation areas and accelerated emission of greenhouses gases (Steffen and Tyson, 2001). The depletion of vegetal cover adversely affects various ecosystems by way of biodiversity loss, wildlife habitat, food supply, medicinal herbs, pollution, erosion and drought. In recent times, geospatial technologies (remote sensing and geographical information system have proven to be the most cost effective and time-saving tools for monitoring land use/cover change at large spatial and temporal (Agbor et al., 2012 andShao et al, 2017). The importance of vegetation in the environment cannot be underestimated when considered against the backdrop of the role it plays as a major carbon sink, microclimate moderation and for aesthetics (Ige et al., 2017). Therefore, this study would attempt to map the status of land use land cover change (LULCC) of Enugu city in Enugu state over a 30 year period (1989-2019) to estimate the rate of vegetal cover loss as a result of urban expansion. Also, this study would venture into scrutinizing the impact of deforestation on temperature in Enugu city.

Objective
The objectives of this study are to detect the changes in Enugu City metropolis from 1989-2019, determine the change in temperature from 1989-2019 and model forest change using temperature.

The Study Area
Enugu city is the capital of Enugu State. It is located in southeastern Nigeria. The. The name Enugu is derived from the two Igbo words Énú Ụǵwụ́ meaning "hill top" denoting the city's hilly geography. The city was named after Enugwu Ngwo, under which coal was found. There are three local government areas in the city namely Enugu East, Enugu North and Enugu South. It is between longitude 6 o .23' N and 6 o .38 ' N and latitude 7 o 25 ' Eand 7 o 39 ' N of the equator. It is bordered in the east by Nkanu East local government area and west by Udi Local Government Area respectively, in the south by the Nkanu west, and towards the north by Igbo Eti local government area of Enugu State. It spans across an area of about 560km 2 . According to 2006 census, the total population is 722,664 (NPC,2006). Its elevation is about 590ft (180m). It is signi cant for its coal mining activities.
The Ekulu, Asata, Ogbete, Aria, Idaw and Nyaba rivers are the six largest rivers located in the city. The Ekulu River is the largest body of water in Enugu urbanand its reservoir contributes to part of the city's domestic water supply. Enugu is located in a tropical rain forest zone with a derived savannah. The city has a tropical savanna climate. It's climate is humid and this humidity is at its highest between March and November. For the whole of Enugu State the mean daily temperature is 26.7 °C (80.1 °F) (Sanni, 2007) 3.2 MATERIALS

Data used and source
Landsat satellite images of the study area for 1989, 1999, 2009,2019 were obtained from USGS Earth Explorer o cial website. Another important data used is the road network of the study area.  (Shao et al, 2017) i. ArcGIS 10.5 software (ESRI) was used to generate various thematic layers.
ii. Microsoft O ce package came very handy for the correlation analysis and the presentation of the work.

Image Processing
Geometric recti cation is critical for producing spatially corrected maps of land use/cover changes through time. The Landsat TM, ETM+ and OLI images were in UTM projection (Zone 31N) on WGS84. Therefore, the images of the study area were geometrically corrected. The color composites for the four images were generated from Landsat TM, ETM+ and OLI bands 2, 3, 4, and 5. These color composites were selected to for training sites for land use/land cover extraction. The images were classi ed using supervised classi cation i.e. maximum likelihood classi er algorithm, which provides a consistent approach to parameter estimation problem. It can be applied in reliability analysis to censored data. From the classi ed images, the land use/land cover (LULC) maps were extracted and the requisite statistics generated thereafter. The classi cation scheme utilized only three land use classes representing built-up area, vegetation and water body. The post interpretation phase included preparation of land use maps and detection of their changes. A greater part of the analysis was predicated on the post-classi cation comparison approach. It was employed for analyzing land use/cover changes, by comparing independently produced classi ed land use/cover maps. The main advantage of this method is that it has capability to provide descriptive information on the nature of changes that occurs (Mundia andAniya, 2005., Alboody et al., 2008

Average Rate of Change
The average rate of change describes the rate at which one quantity is changing with respect to something else changing. In other words, it calculates the amount of change in one item divided by the corresponding amount of change in another item Average rate of change (ARC) = Where: f(x) -f(a) = the change in the function "f" as the input changes from "a" to "z" x -a = the change in the input of the f function.

Correlation Analysis
Most of the changes in land use land cover depend on certain factors like roads, commerce, topography, population e.t.c. This study considered the contributions of expansion rate of the study area over the years. Vegetation was considered dependent variable while temperature was considered independent variable. Correlation analysis was carried out to assess the degree of relationship among the variables.

Results And Discussion
The results are presented in this chapter in form of maps, and statistical tables. They include the land cover types, change statistics and weather variable such as temperature, and the relationship that exist between temperature and vegetation cover over the years.

Analysis of Land Use Changes and Dynamics of Urban Expansion in Enugu
The urban change analysis is based on the statistical data extracted from the three-different land use and land cover maps of the classi ed images (Figures 2,)   In Table 3,

Temperature Pattern of the Enugu city
In (Table 3)  The temperature map from the analysis shows the temperature distribution of Enugu city in pixels (30x30). The non vegetation area has the lowest temperature while the built up area has the highest temperature. Also, both temperature and vegetation graphs show that the area experienced decrease in vegetation cover over the course of years, while temperature was in the increase. Also, area of low vegetation has high temperature and vice versa from the temperature images. This has been determined by carrying out Correlation Analysis between temperature and NDVI.

Conclusion And Recommendation
From the analysis, we can deduce that what was lost in vegetation was gained by built-up and that urbanization and industrialization are major factors of loss of green vegetation. Density of roads and elevation showed positive relationships with urban expansion between 1989 and 2019. Planners and policy-makers should put more premiums on the increase in land consumption rate and pattern when looking at urban morphology. They can achieve this by critically evaluating the spaces for future urban expansion, encouraging the construction of highrise buildings, and the opening of the peri-urban through the construction of access roads.
Also, the results obtained from this study should raise strong concerns for environmental managers involved with the mitigation of the effect climate change in and around Enugu city. With increasing percentage of built up areas through industrialization and urbanization, the temperature of the city will also continue to be on the rise. The future urban land use planners, the analysts and the policy makers in the state should consider urban space management for land allocation in the future. They study can provide important insights on why it's essential to encourage urban forestry as a way to mitigate the effect of vegetation loss.

Figure 2
LULC map between 1989 and 2019 Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

Figure 3
NDVI map between 1989 and 2019 Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.