Land use/Land Cover Changes and Causes of Deforestation in the Wilberforce Island, Bayelsa State, Nigeria

The objective of this paper is to provide the non-existent data on land use/land cover changes in the Wilberforce Island for the purposes of determining the causes of deforestation and changes in the vegetation cover for a 13 – year period. Accordingly, 125 questionnaires were administered in five communities to determine the causes of deforestation. Satellite imageries for 2002 and 2015 were also acquired from Landsat 7 and 8 respectively and analysed with the Quantum Geography Information System (QGIS) software to obtain the various land use/land cover changes. The semi – Automatic Classification Plugin Version 4.9.1 of the QGIS was used for the land use/land cover classification with a supervised classification method. Each satellite imagery was classified into 8 categories using their reflectance values and the error matrix was used to show the level of accuracy of the classified imageries. Results from the study indicated that the major drivers of deforestation were logging, farming, building of houses and fuel wood fetching. Results from satellite imageries also showed that forest and sparse vegetation/grassland decreased from 73.34% and 10.32% to 51.34% and 8.08% between 2002 and 2015 respectively, while farmland and residential area increased from 10.71% and 0.44% to 30.575 and 1.72% for the same period respectively. It was concluded that land use/cover changes was due to deforestation to provide raw materials for wood industries, and space for agriculture and building of house for the increasing population in the area. The implications of deforestation for biodiversity and climate change have been highlighted.  Keywords : Deforestation, land use/land cover changes, Wilberforce Island

Land use involves the management and modification of natural environment or wilderness into built environment such as settlements and semi-natural habitats such as arable fields, pastures, and managed woods, while Land cover is the physical material at the surface of the earth and includes grass, asphalt, trees, bare ground, water, etc (Wikipedia, 2017).Deforestation is a global environmental hazard leading to land use and land cover changes.According to the United Nation Food and Agriculture Organization (FAO) (2010), the global forests declined by about 5.2 million hectares every year between the year 2000 and 2010.Nigeria has one of the highest rates of deforestation in the world, having continuously lost about 410,100 hectare per year between 2005 and 2010 at a rate of 3.12% per annum (Ozor & Odo, 2008).The main drivers of deforestation in the country have been agriculture, logging, grazing, urbanisation, road construction and mining (FAO, 2010;Ozor & Odo, 2008).Nigeria could face the possibility of timber and fuelwood scarcity towards the end of the century (Aliyu, Modibbo, Madugu & Ayo, 2014).
Deforestation has many negative effects on the environment.The most dramatic impact is loss of habitat for millions of species with serious implication for eco -tourism and loss of biodiversity.Deforestation also drives climate change (National Geographic, 2015), and is considered to be one of the contributing factors to global climate change (Bradford, 2015).
While there are records of the causes and levels of deforestation in many parts of Nigeria, there are no records of how much forest cover have been lost to human activities or what the major cause(s) of deforestation in the Wilberforce Island are.The objectives of this study is therefore to provide the non-existent data on land use land cover changes in the Wilberforce Island for the purposes of determining the causes of deforestation and changes in the vegetation cover for a 13 -year period.

MATERIALS AND METHODS
The study area: The Wilberforce Island is located between latitude 4 o 51′N to 5 o 02′N, and longitude 6 o 04′E to 6 o 17′E.The area cuts across Kolokuma-Opokuma, Yenagoa, Southern Ijaw and Sagbama Local Government Areas in Bayelsa State and is drained mainly by the Nun River which is a distributary of the River Niger.Vegetation is the tropical rainforest which encourages lumbering.The Island hosts the Niger Delta University, whose establishment in 2000 has encouraged massive population influx into the Island leading to a rapid change in land use and land cover.Primary and secondary data were used for this study.Primary data was obtained through the administration of self -administered questionnaires.One Hundred and Twenty-Five (125) questionnaires were administered in five communities (Amassoma, Ogobiri, Agudama/Ekpetiama, Igbedi and Bumoudi) selected from the Wilberforce Island using the purposeful sampling technique for this study.The questionnaires were designed to obtain information regarding the level of awareness of deforestation activity and its major causes in the study area.The primary data obtained were analyzed with the Measures of Central Tendency and Proportions, as well as ranks.
The secondary data for this study were the satellite imageries of 2002 and 2015, which were acquired from Landsat 7 and Landsat 8 respectively.These images were analysed with the Quantum Geographic Information System (QGIS) Software to obtain the various land use/land cover of the study area.Characteristics of these acquired satellite imageries are shown in Table 1.The Semi-Automatic Classification Plugin Version 4.9.1 of the QGIS software was used for the land use/land cover classification with a supervised classification method.Each satellite imagery was classified into 8 categories (Table 2) using their reflectance values and the error matrix was used to show the level of accuracy of the classified imageries (Table 5 & 6

RESULTS AND DISCUSSION
Result from the study showed that 97.6% of the respondents were aware of deforestation activities going on in the Wilberforce Island.With respect to the causes of deforestation in the Wilberforce Island, results indicated that logging and farming were the most significant (Table 3).Most respondents in the study ranked logging as the major cause of deforestation in the study area, followed by farming.
The results obtained from the study were found to be similar to those of Akinyemi (2013) and FAO (2010), which confirmed rapid population growth, agricultural expansion, use of fuelwood and logging as the major drivers of deforestation in the Southern part of Nigeria.The result presented in Table 4 shows the area of each Land use/Land cover category for 2002 and 2015.In 2002, Forest and sparse vegetation occupied 73.34% and 10.32% of the total land area respectively.This implied that the total Vegetation cover was 83.80% of the total land area.On the other hand residential area occupied 0.44% of the total land area while farmland occupied 10.71% of the total land area.By 2015, Forest cover accounted for only 51.34% of the total land area, showing a decrease of 30.02% of its original cover.Also, Sparse Vegetation occupied 8.08% of the total land area, showing a reduction of 21.75% of its original cover (Figure 2 & 3).Farmland now occupied 30.57% of the total land area, showing an increase of 185.35% of its original cover; and Residential Area occupied 1.72% of the total land mass, showing an increase of 290.83% of its original cover.This implied the vegetation cover in the study area decreased considerably within the 13 years' time-frame principally as a result of the increase in the residential areas and farmlands (Table 7).(-) indicates decrease.

Conclusion:
It can be concluded from the study that logging, farming, building of houses and fuel wood fetching are the major causes of deforestation and the observed land use and land cover changes in the Wilberforce Island.The massive reduction in the forest cover, and the associated land use and land cover changes in the study area were due to rapid increase in population following the establishment of the Niger Delta University, and the consequent need for raw materials for wood industries, and space for agriculture to support the burgeoning population as well as for building of houses.This however calls for urgent action to control the high rate of deforestation in the light of current global issues such as global warming and climate change amongst others that requires the protection of the forest.
Land use/Land Cover Changes and Causes of Deforestation 1064 BARIWENI, PEREKIBINA A.; ANDREW, COMFORT, E.

Fig 1 :
Fig 1: The Wilberforce Island ).The level of deforestation was assessed with the Post-Classification Comparison Method to detect changes in the classified images of 2002 and 2015.
cover analysis results obtained from the classified satellite imageries used for the study.The classified imageries of 2002 and 2015 are shown in Figure 2 and 3.

Table 1 :
Characteristics of the Acquired Satellite Imageries

Table 2 :
Land use -Land cover Classification Scheme and their General Descriptions

Table 3 :
Causes of Deforestation in the Study Area as Ranked by The level of deforestation in the study area was detected after applying a Post-Classification Comparison Method (Table 7) to the Land use/Land Land use/Land Cover Changes and Causes of Deforestation 1065 BARIWENI, PEREKIBINA A.; ANDREW, COMFORT, E.

Table 4 :
The Land use/Land cover of Wilberforce Island 2002 and 2015

Table 5 :
Error Matrix of the Classified Imagery of 2002

Table 6 :
Error Matrix of the Classified Imagery of 2015

Table 7 :
The Land use/Land cover Changes in the Wilberforce Island(2002 -2015)