Assessment and Trend of Land Cover Land Use Changes in Owerri and Environs, South Eastern Nigeria

This study examined land cover and land use changes (LCLUC) in Owerri and environs from 1986 to 2016 and went further to determine the trend in the change of each LCLUC class. The satellite imagery of the area over the three decades was characterized into the different LCLUC classes and the changes in the areal extent of the different LCLUC classes were calculated and plotted, followed with the estimation of the trend using linear regression analysis method. The result revealed that over the three decades, forests and sparse vegetation respectively decreased at a rate of 0.73% and 0.05% of the total land area per year while built up areas increased almost equally in the opposite direction at a rate of 0.65% of the total land area per year. Open spaces and water bodies decreased at the rate of 0.11% and 0.02% of the total land area respectively which were as a result of the pressure for resources like land and sand for built infrastructure. A model was derived for the LCLUC and it revealed that Owerri and environs may be devoid of vegetal cover in about 2 decades (2039) if the current rate of conversion of forests to built-up infrastructure is not abated. This whole LCLUC scenario if not controlled may trigger changes in the local climate of the area and urgent steps are therefore needed to create awareness to all the stakeholders in the area on the need for sustainable land and natural resources use, tree planting, urban spatial plan and controls in order to safeguard the environment, ecosystem and climate of the area for the future.

vironment and when this has taken place over a length of time causing an irretrievable transformation of the landscape, it is termed land use changes (LUC) or more generally land cover and land use changes (LCLUC). Land use is thus characterized by the arrangements, activities and inputs people undertake in a certain land cover type to produce, change or maintain it [1], and these arrangements, activities and inputs which include farming, housing, landscaping, amenities and infrastructure amongst others are as old as human evolution from the Neolithic time through the Holocene to the present day era. Other actions of human that change the landscape are deforestation, agriculture, urbanization, afforestation, reforestation, dumping of refuse and alterations to city planning, to mention a few. In Indonesia for instance, about 500 sq km of forest is cleared each year, much of which is replaced with oil palm plantation [2].
At a global scale and on a historical perspective, the model of the transition of land use from pristine natural ecosystem to modern day intensive agriculture and urbanization is shown in the figure (Figure 1). This has been defined to mean a transition from natural vegetation cover to frontier clearing, then to subsistence agriculture and small scale farming and finally to present day intensive commercial agriculture, urbanization, recreational parks, forest reserves, etc. [3].
Thus, agriculture and urbanization are major activities that lead to changes in land use, for the reason that an increase in population leads primarily to the demand for shelter and food and subsequently, amenities, industries and commercial housing. The model thus described is not universal, because it may not be simultaneously fit into all regions of the world, due to the peculiar circumstances like socio-political and economic situations which a region may be facing. The rate of transition for any nation or locality can be linear or non-linear depending on any of the circumstances just mentioned. For instance, some regions may be static on a particular transitional stage for too long, like infrastructure, due to  land use classes into built-up and riparian land and water bodies converted to major sand excavation sites [6]. These activities at that time could be as a result of increases in economic activities, infrastructural development or population growth (when projected from the 2006 population census data [7]).
With all these happenings, therefore, the study area can benefit from a probabilistic estimation of the transition of a particular LCLUC class into another, using tools like Markov Chain which Eludoyin et al. [8] have used to forecast the LCLUC transition in the nearby ObioAkpor LGA, Nigeria. Several scholars [9] [10] [11] have used it or its variants at other locations. Therefore forecasting the transition of vegetal covers into built up space is apt for Owerri and environs and other parts of the country experiencing the same rapid LCLUC transformations.
Apart from direct (or human-caused) changes to land cover, land use changes can also result indirectly from nature like volcanic eruptions, earthquakes, landslides, mudslides, flooding, drought and hurricanes amongst others, but these natural events have not occurred in Owerri and environs in recent or past memory.
Several studies have indicated that land-use change is a driver of climate change through changes in greenhouse gas, especially carbon dioxide (CO 2 ) emissions from the land and changes in energy and water balance at land surface [12]. The Intergovernmental Panel on Climate Change (IPCC) estimates that land use change (e.g. conversion of forest to agricultural land) contributes 1.6 ± 0.8 Gt carbon per year to the atmosphere [13]. Onyenechere, in his study revealed the increase in ambient air temperature in Calabar, Lagos and Kano [14].
In a recent study, Echebima et al. revealed that on average, the climate of Owerri and environs has changed and is warming up, though not at a uniform rate [15]. Therefore, the study is concerned with land cover and land use changes (LCLUC) resulting from human activities in Owerri and environs from 1986 to 2016 and will further determine the rate of change (trend) of each LCLUC class which for consistency and comparison with previous studies and based on Anderson et al. [16], will use the following LCLUC classification namely Built-up area, Farmland or sparse vegetation, Open space, Forest or thick vegetation and Water body. The study will not only gave the empirical data on the changes of each LCLUC class in each decade studied, but will further adopt a novelty approach to use linear regression methods of line of best fit to determine the overall trend, pattern of LCLUC and behavior of natural resource use from which a projection/forecast can be made of the future size a particular LCLUC class.

The Study Area
The study area is Owerri urban and parts of its adjacent periurban towns delimited by the coordinates shown in the table (Table 1) and depicted in the figure ( Figure 2). The area encompasses the entire Owerri municipal council and parts of the adjacent councils namely Owerri West LGA and Owerri North LGA. Two rivers namely, Otamiri flowing from the East and Nworie flowing from the west interspersed the study area and has a confluence at a point in Owerri town which then flows down south. The vegetation of the area is dominantly tropical rainforest with herbaceous plants forming the forest floor while trees form the canopies, but the density of the rainforest has drastically been reduced over the years due to human activities. Interspaced are light or sparse vegetation comprised mainly of shrubs and farm plants. The climate of the area is a tropical wet climate or monsoon climate according to the Koppen-Geiger weather classification [17], characterized by high temperature and humidity. It has both wet Table 1. The corner coordinates of the study area (refer to Figure 4 for the corner points).

Materials and Methods
Land Satellite (Landsat) imagery data and local maps for geo-reference were    [19], FAO [20] for land cover and land use class classifications. On this note therefore, this study adopted five classes based on the geography of the study area and in conformity with other scholars particularly Okeke, Nnaji, et al., Njoku, et al. [21] and Ukaegbu, et al., [22] which are: open spaces, forest (or

Results and Discussion
The results of the work are presented starting with the LCLUC in the years 1986, 2000 and 2016 studied and thereafter followed with the trend analysis.

1986 Land Cover Land Use Changes in the Study Area
The result of the LCLUC classification for 1986 is depicted in Figure 3 and summarized in Table 3

2000 Land Cover Land Use Changes in the Study Area
The spatial distribution for LCLUC classes in the year 2000 is shown in Table 4 and   98.82 hectares respectively tallying about 1.29% and 1.21% respectively of the entire study area.

2016 Land Cover Land Use Changes in the Study Area
In 2016 as the results revealed in Table 5 and Figure 5, Built-up area became the dominant land cover, occupying a total of 4410.72 hectares making up about 54.10% t of the entire study area, now followed by farm/sparse vegetation cover which made up 1881.9 hectares which is about 23.08% of the entire study area.

Change Detection Analysis
The change detection analysis which was created by superimposing layer by layer, the land use forms from the years 1986, 2000 and 2016 is shown in Figure 6. Thus  2016 occupying more than half of the study area as depicted in Figure 6. Thus, land use transitional model through those decades can be summarized as high and fast forest depletion and an inversely high and fast rate in the built-up cover. These changes in the LCLUC class, as the years progressed from 1986 through 2000 to 2016, is summarized in Table 6 with negative (−ve) or positive (+ve) differences signifying depletion or growth in the LCLUC class. That farm/vegetation was fluctuating between the years of this study, may signify that there is an earlier need for food as population grows, but after the year 2000, there is pressure on the land for housing. Another important observation is the increase in water bodies which "ground truth" visit to Otamiri and Nworie rivers revealed massive sand harvesting at the river bed and river banks and also abuse of riparian lands for physical structures. In like manner, the increase in open spaces in 2016 are not necessarily leisure parks, play grounds or open spaces in its real sense, because pre-existing ones have been encroached upon due to pressure on land for physical infrastructure. The increase in open spaces is the deforested areas that have been cleared, preparatory for buildings.

Trend in Land Cover Land Use from 1986 to 2016
The percentage of space occupied by each land cover land use class is shown in  Table 7.
The data in Table 7 is then transposed into a graph and linear regression analysescarried out in order to determine the trend (or rate of change per year) in LCLUC class in Owerri and environs. The results are shown in Figure 7(a) and Figure 7(b).
From, the graphs in Figure 7(a) and Figure 7    6) Sand excavation on the banks of the river and physical structures is depleting the riparian lands, with its attendant consequences.

Conclusions
Within the period under study from 1986 to 2016, we can conclude as follows that: 1) Adverse Land Cover and Land Use Changes have taken place in Owerri and environs leading to a high rate of loss of combined thick and sparse vegetal cover at 0.78% of the land cover per year, with the implication of changing the local climate of the area.
2) Urbanization has increased with little or no spatial planning or controls at 3) Consequent upon item 2 above, Open spaces and water bodies marginally increased respectively at 0.11% per year and 0.02% per year of the total land mass due perhaps to opened-up forest/vegetal cover and sand harvesting at the banks/beds of Otamiri River and Nworie River.
4) The riparian lands surrounding the two rivers (Otamiri and Nworie) have suffered depletion due to encroachment. 5) At the rate of conversion of vegetal cover to built-up infrastructure, if it is not arrested and proper urban re-planning with greening followed, the entire vegetation in the area could be depleted in about 2 decades in 2039.

Recommendations
Based on the findings of the study, we make the following recommendations: 1) There is a need to urgently limit and control the high rate of deforestation going on in Owerri and environs and embark on tree planting campaigns without delay by all stakeholders.
2) Urbanization and other infrastructural developmental efforts should be approached by the government through proper urban spatial planning and controls, sustainable land and natural resources use.
3) There is need to embark on water shed management of the Otamiri River