Assessment of Urban Encroachment on Agricultural Land in Offa Local Government Area, Kwara State, Nigeria
AIM AND OBJECTIVES OF THE STUDY
The aim of this study is to assess urban expansion on agricultural lands in Offa LGA between 1990 – 2014. The specific objectives of the study are to:
- map out different land use types in the area in 1990, 1999 and
- determine the extent and rate of urban growth in Offa between 1990 and 2014
- determine the conversion rate of agricultural lands to urban
CONCEPTUAL FRAMEWORK LITERATURE REVIEW
This chapter reviews extant literatures on urban expansion. The first part reviews literatures on the definition of major concepts such as urban expansion, causes and consequences; urbanization, urban areas, and agricultural land. While the following part deal with Geographical Information System (GIS), Remote Sensing; and the application of Remote Sensing and Geographical Information System GIS in Urban studies, growth and dynamics (detecting and monitoring, measuring and analyzing urban expansion).
Opinions are far from various on the concept of urban expansion. However, Manish, Aruna and Vivek (2012) define urban expansion as the horizontal or vertical outward extension of urban area over the adjacent agricultural land, which can be measured in term of acres of land or in terms of percentage (actual or percentage expansion respectively). The percent expansion refers to the percentage increase in the aerial strength of the urban center over a period of time.
According to Lin, Yohei, and Haihong (2003) Urban expansion is a natural process which consumes many hectares of prime agricultural lands from their surrounding every year, it comes about through the transformation of non-urban land (for example, farmland) into urban land (such as residences, parks, shops and factories). He further argued that such transformation is one way; once transformed, it is very difficult to return back to the original land use. Thus, urban expansion, like a diffusion process, is also temporal but it is not strictly continuous in time.
Minwuyelet (2004), also see urban expansion as a worldwide phenomenon or process that involves both the internal reorganization and outward expansion of the physical structure of urban areas which results in loss of prime agricultural farmlands and natural beauties. This process could be seen in the history of all urban centers, although the term (urban expansion) has become synonymous with the creation of visual blight and the loss of natural habitat, not all of its effects are negative. In its simplest form, it is nothing more than expansion which normally occurs away from the dense areas of existing urban development. The need for urban expansion continues to escalate as the population continues to increase (Almeida, 2005; Shishay, 2011).
However, European Environment Agency (2006), describes urban expansion as the physical pattern of low-density expansion of large urban areas, under market conditions, mainly into the surrounding agricultural areas where development is patchy, scattered and strung out, with a tendency for discontinuity. It is seen as „horizontal spreading‟ or „dispersed urbanization‟, uncontrolled and disproportionate expansion of an urban area into the surrounding countryside, forming low-density, poorly planned patterns of development and common in both high-income and low-income countries.
THE STUDY AREA AND METHODOLOGY
This section discusses the study area and the various methods that were employed in generating data for the study. The section also explained the types and sources of data, tools and procedure for data analysis using Remote Sensing and GIS in the study area.
Offa is a traditional ancient and Nigerian town, which like other such towns in the country exists long before the advent of British colonial rule. There is no exact information on the age of the town but it is commonly believed that the original settlers were Yoruba from Ile – Ife which is widely regarded as the main origin of the Yoruba people.
Traditionally, the town is divided into four major quarters known as Esa, Ojomu, Shawo and Balogun, each of these quarters is managed by a local chief who assist the „Olofa‟ (traditional king of Offa) in their governance and have their individual office named after this quarters. These quarters still maintained their names till today even though they even been further segregated for political governance.
RESULTS AND DISCUSSION
This chapter dwells on the presentation and analysis of result obtained from the research analysis; the objectives of this study formed the basis of all the analysis carried out in this chapter. The results are presented in figures 4.1, 4.2, 4.3 4.4; and tables 4.1, 4.2, 4.3. and 4.4. The presentation and analysis of the data have been carried out under the following sub- themes; land use and land cover classes; extent, percentage and rate of land use land cover change; spatial loss of agricultural land to other land uses; and the rate of agricultural land conversion to urban built – up (urban expansion) trend, pattern and rate of land use land cover change.
DIFFERENT LAND USE TYPES IN THE STUDY AREA
The mapping out of different land use types of Offa Local Government Area in 1990, 1999 and 2014 was carried out by classifying and polygonising the satellite imageries into five major land use types as stated earlier. See Fig 4.1
SUMMARY, CONCLUSION AND RECOMMENDATION
This chapter describes the summary of the major findings of this study, conclusion derived from the findings and recommendations for effective management and reducing the impact of urban expansion particularly on agricultural land in the study area and the state at large.
SUMMARY OF THE MAJOR FINDINGS
This research provide insight on the impact of urban expansion of agricultural land in Offa Local Government Area using Remote Sensing and GIS. Attempt was made to capture as accurate as possible the five major land uses types in the study area as they change through time. The study used Remote Sensing and GIS as an analytical tool with satellite images used for mapping and quantifying the land use types, rate and extent of urban growth, spatial loss and conversion of agricultural land to other land use and urban expansion within the study period.
As shown from the classified land use classes, land use types had changed significantly over the period of more than two decades (1990 – 2014). The statistics indicated that the growth rate of built up area occupied the largest share among land use categories especially at the expense of agricultural land. It shows a rapid decline in agricultural land between 1999 and 2014 while the period between 1990 and 1999 witnessed relatively slow decline. The lost agricultural land between these periods was converted to urban land use (built up and bare surfaces).
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