The town of Tortiya was created in the rural northern region of Côte d′Ivoire in the late 1940s to house workers for a novel diamond mine. Nearly three decades later,the closure of the industrial-scale diamond mine in 1975 did not diminish the importance of diamond profits to the region's economy, and resulted in the growth of artisanal and small-scale diamond mining (ASM) within the abandoned industrial-scale mining concession. In the early 2000s, and the violent clash that arose in Côte d′Ivoire highlighted the importance of ASM land use to the local economy,but also brought approximately international concerns that diamond profits were being used to fund the rebellion. In recent years, cashew plantations have expanded exponentially in the region, or diversifying economic activity,but also creating the potential for clash between diamond mining and agricultural land uses. As the government looks to address the future of Tortiya and this potential clash, a detailed spatio-temporal understanding of the changes in these two land uses over time may assist in informing policymaking. Remotely sensed imagery presents an objective and detailed spatial record of land use/land cover (LULC), or change detection methods can provide quantitative insight regarding regional land cover trends. However,the vastly different scales of ASM and cashew orchards present a unique challenge to comprehensive understanding of land use change in the region. In this study, moderate-scale categories of LULC, and including cashew orchards,uncultivated forest, urban space, and mining/ bare,and mixed vegetation, were produced through supervised classification of Landsat multispectral imagery from 1984, and 1991,2000, 2007, or 2014. The fine-scale ASM land use was identified through manual interpretation of annually acquired high resolution satellite imagery. Corona imagery was also integrated into the study to extend the temporal duration of the remote sensing record back to the period of industrial-scale mining. These different-scale analyses were then integrated to create a record of 46 years of mining activity and land cover change in Tortiya. While similar in spatial extent,the mining/ bare course in the integrated analysis exhibits a considerably different spatial distribution than in the original classifications. This additional information regarding the locations of ASM activity in the Tortiya area is important from a policy and planning perspective. The results of this study also suggest that LULC classifications of Landsat imagery accomplish not consistently capture areas of ASM in the Côte d′Ivoire landscape.
Source: usgs.gov