Research Journal of Applied Sciences, Engineering and Technology 2(2): 121-132, 2010 ISSN: 2040-7467 © Maxwell Scientific Organization, 2010 Submitted Date: September 12, 2009 Accepted Date: November 18, 2009 Published Date: March 10, 2010 Assessing Changes in Kagoro Forest, Kaduna State Nigeria using Remote Sensing and Gis 1Ojonigu F. Ati, 1Tabitha Sheyin, 1Innocent Abbas and 2Seidu O. Mohammed 1Geography Department Ahmadu Bello University, Zaria, Nigeria 2National Centre for Remote Sensing, Jos National Space Research and Development Agency Ministry of Science and Technology Abstract: Already georeferenced satellite imageries for 1987, 1994 and 2005 were used to study the land cover changes in the Kagoro forest. The results of the study revealed that settlement and cultivated area increased between 1987 and 2005 by 72 and 17.77% respectively while undisturbed forest decreased 24.06%. This result shows a significant depletion of the Kagoro forest as a consequence of human activities particularly cultivation for agricultural purposes. At the present rate, the forest is in danger of being destroyed and laid bare in the nearest future. This trend has implication for global carbon dioxide loading and temperature. Key words: Land cover, forest, cultivation, carbon dioxide, temperature, settlement INTRODUCTION vegetation. The energy and the high cost of kerosene have caused recourse to firewood as an alternative source of Pressures on forest especially in the tropical world, to energy for domestic uses. A dimension is added by the provide economic resources have been increasing rapidly felling and burning of wood to produce charcoal and this as a consequence of burgeoning population in the region. is causing serious depletion of forest resources. According This has led to unabated deforestation, which has been to Oyebo (2006) Nigeria has a total of 1,160 constituted recognized as one of the major drivers of biodiversity loss forest reserves, covering a total land area of 10, 752,702 as well as a threat to the existence of the global ecological hectares, representing about 10% of the total land area. lung (Salami, 2006). According to FAO Forest Resource Most of the forests in Nigeria are man-made for the Assessment (2005) each year about 13 million hectares of purpose of timber exploitation, and in some cases for fuel the world's forests are lost due to deforestation, but the wood and furniture making industries. The total plantation rate of net forest loss is slowing down, thanks to new hectarage in Nigeria was estimated at 269,000 hectares in planting and natural expansion of existing forests. From 1988. They compose of 109,377 hectares of Gmelina 1990 to 2000, the net forest loss was 8.9 million hectares arborea and 159,623 hectares of others. The Free areas, per year. From 2000 to 2005, the net forest loss was 7.3 which are land use types located outside forest and games million hectares per year - an area the size of Sierra Leone reserves are 9,136,726 hectares. These have major forest or Panama and equivalent to 200 km2 per day. Primary types dominantly trees/woodlands/shrubs (5,611,392 ha), forests are lost or modified at a rate of 6 million hectares lowland rain forest (1,187,488 ha) and freshwater swamp per year through deforestation or selective logging. forest (1,430,175 ha) (Oyebo, 2006). Plantation forests are established at a rate of 2.8 million Forests are important in the maintenance of an hectares per year. The ten countries with the largest net attractive forest environment, provision of opportunity for forest loss per year between 2000 and 2005 (Brazil, relatively intense outdoor recreation, provision of habitat Indonesia, Sudan, Myanmar, Zambia, United Republic of for wildlife, watershed function, general conservation Tanzania, Nigeria, Democratic Republic of the Congo, including minimization of soil erosion and the production Zimbabwe, Venezuela (Bolivarian Republic of)) had a of wood for various uses (Aweto, 1990). Forest also combined net forest loss of 8.2 million hectares per year. serves as effective sink for carbon dioxide and releases Thirty-seven countries and territories lost 1 percent or oxygen from its photosynthetic activity. more of their forest area each year between 2000 and The Kagoro forest is a natural rain forest type of 2005, while 20 countries gained more than 1 percent per vegetation within the savannah. This is because of the year due to natural expansion of forests and afforestation. location of the forest on the south-western slope of the In Nigeria, about 350,000 to 400,000 hectares of plateau. Kagoro is on the windward side of the plateau forest is being lost per annum (Oyebo, 2006). This thereby experiencing more rain than the surrounding situation is brought about by over exploitation due to the environment. The forest is located between 9º22 and 9º35 demand for food, energy and fodder and also through and 8º11 and 8º24 in Kagoro District of Kaura Local illegal logging and non-replacement of the natural Government Area of Kaduna state. The area is located in Corresponding Author: Ojonigu F. Ati, Department of Geography Ahmadu Bello University, Zaria, Nigeria 121 Res. J. Appl. Sci. Eng. Technol., 2(2): 121-132, 2010 the sudan savannah which characteristically experiences MATERIALS AND METHODS the tropical wet-dry climate with about seven months of rainfall between April and October and five months of dry Data: Data was acquired from Land sat TM (30m season from November to March. The vegetation is a resolution) imageries 1987 (Fig. 1). mosaic of savannah and forest with forest occurring SPOT XS (20m resolution) 1994 (Fig. 2) mainly in river and stream valleys, but also elsewhere due Land sat ETM (15m resolution) satellite 2005 (Fig. 3). to high annual precipitation of more than 1,550 mm (Ezealor, 2001, 2002). The district is recognized as one of Software: Earth Resource Data positioning System the centres for agriculture which provides raw materials (ERDAS) version 8.3.1, for industrial use and commerce especially in the southern Arc View 3.2a part of Kaduna state, and as such the area has been The imageries were already geo-referenced to UTM mode; this process involves relating the coordinates of the attracting an appreciable amount of developmental study area to that of the map (that is relating coordinates services. In response to this, several transformations have on map to those on the ground). The imageries came in taken place in such sectors. For instance, growing scenes, with one scene larger than the study area, in order industries require raw materials for their manufacturing to get the study area; the outline of the coordinates of the hence endangering the Kagoro forest; they also need to study area was used to subset the scene to get the outline site their industries close enough to their raw materials, on the imageries. The process of subset is getting the and housing quarters may also have to be built for such study area through the whole area. workers. Since such sectors have direct bearing with the land, it is expected that their developments would be Interpretation: Onscreen visual interpretation was done; associated with the land cover changes in the area. the process of digitization was automatically done The present state of the Kagoro forest hence has a lot together with the interpretation using Arc View 3.2a. First to do with the growing local industries especially there was a creation of sample map which indicated a carpentry where trees are felled and used to make domain, then impact data from the 1987, 1994 and 2005 furniture for offices, and homes and also for the building maps was done after which four basic categories were industry, because many people have left the interior classified. These categories include; cultivated area, rock villages to settle in Kagoro, Kafanchan and other outcrops, settlements, and the undisturbed forest, an neighbouring towns and want to build houses, build interpretation key was used to help in the identification of companies and industries, so the forest has been the features to be identified and interpreted (Fig. 4-6). continually tampered with. This is apart from the growing The first to be interpreted was the cultivated area as prices of fuel and fuel products leading to the cutting of it is also described and identified by the presence of trees for cooking and keeping warm during the cold dry regular patterns of defining light red colour indicating season. crops, at other times very light reflectance were observed The effects of deforestation manifests in the loss of indicating bare surfaces for harvested fields. Secondly, the biodiversity, loss of soil fertility through loss of nutrients, rock outcrops were identified and interpreted as desiccation of previously moist forest soil, dramatic irregularly shaped, exhibiting very fine texture. The increase in temperature extremes, more desertification, colour is greyish, and the reflectance could either be dark less carbon dioxide and nitrogen exchange, loss of or light depending on the mineral constituents of the rock. effective sink for carbon dioxide enhancing global Thirdly, the settlements were identified and also interpreted as mostly irregularly shaped and usually warming and climate change. linked by road networks. They are also identified by their In light of the potential negative effects of such bluish green colour, which is reflective of the roof top changes on land quantity, quality and productivity, materials. The fourth category to be identified and information on the nature and magnitude of such change interpreted was the undisturbed forest, with irregular is certainly needed. This study on the land use/land cover patterns and no signs of cultivation. It is very deep red in changes in the Kagoro forest though on a smaller scale colour, which is associated with the chlorophyll content will provide data on the rate at which forest resources are of fresh vegetation.