Abstract
Abstract. A GIS-based Normalized Differential Vegetation Index (NDVI) was analyzed using space-based data between 1972 and 2011 as Input data. The result of the NDVI using Landsat 7 ETM+ shows clearly that the values range from 0.19 to −0.31. Mountains and highlands of the Itagunmodi-Igun area revealed stressed vegetation cover between 0.11 to −0.31. The NDVI was also performed on Landsat imageries of four different epoch: 1972, 1986, 2000, and 2010. Results showed that vegetation index ranged from −0.105 to 0.033, −0.25 to 0.480, −0.313 to 0.19 and −0.29 to 0.5 in 1972, 1986, 2000 and 2010 respectively. The analysis revealed that the study area experienced an increase in biomass between 1972 and 1986 but with some areas experiencing outright disappearance of vegetation as indicated by the lower bands of index values in 1972 (−0.105) and 1986 (−0.25). The result showed that the Basin experienced a rapid and significant increase in biomass between 2000 and 2010, as indicated by the lower bands of index values in 2000 (−0.291) and 2010 (0.5). The results of the NDVI in 1972 ranged from −0.105 to 0.033 while NDVI in 1986 ranged from −0.25 to 0.480 which indicated a significant increase in the vegetation index. The results of the NDVI in 2000 ranged from 0.291 to 0.5 also indicated a significant increase in the vegetation index. The study concluded that artisanal mining could cause land and vegetation degradation with consequent loss of biodiversity, ecological modification.
Highlights
Mining occurs when there is an extraction of minerals or other geological materials from the earth’s crust; which forms the mineralized package of economic interest to the miner [Oluwafemi, 2018, Oyinloye, 1992]
3.1 Artisanal Gold Mining In Itagunmodi-Igun Drainage Basin The condition of the immediate environment of the six gold mine sites that were visited during the reconnaissance and field study namely Asegbon 1, Asegbon 2, Itagunmodi 1, Itagunmodi 2, Itagunmodi 3, and Igun 1 (Abandoned gold mining site) Table 1.1 The area of the mining sites ranges from 50-100m2 and the site condition is poorly drained with clayed soil (Oluwafemi, 2018)
The Normalized Differential Vegetation Index (NDVI) values of the study area reveal clearly that the vegetation has been impacted along the stream-heads and river channels; these impacted areas are due to mining of Sediment-Hosted Disseminated Gold Deposits (SHDGD)
Summary
Mining occurs when there is an extraction of minerals or other geological materials from the earth’s crust; which forms the mineralized package of economic interest to the miner [Oluwafemi, 2018, Oyinloye, 1992]. Gold with the chemical symbol (Au) coined from the Latin word aurum falls into the categories of transition metals It can occur as nuggets or grains, in rocks veins or alluvial deposits. Several studies exist on the impact of mining on the environment both at micro and macro levels (Schueler, et al, 2011; Oyinloye, 1996; Ako et al, 2014; Hawas et al, 2013). Few studies, (Hawas et al, 2013; Oyinloye, 1996; Ako et al, 2014) especially in the field of Geoinformatics, have examined mining and it’s impact on the geomorphology and social well being in a comparative manner. It is interesting to know that the most resourceful gold occurrences in Nigeria are found in the Maru, Anka, Malele, Tsohon Birin Gwari-Kwaga, Gurma, Bin Yauri, Luku, Okolom-Dogondaji, Itagunmodi, Igun and Iperindo areas, all associated with the schist belts of northwest and southwest Nigeria
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