Direct Effects of Mining Activities on Land Resources Around the Pô-Nazinga-Sissili Ecological Complex in Burkina Faso

In Burkina Faso, protected areas have faced various pressures from local actors over the past decades, resulting in a loss of biodiversity. The PONASI ecological complex, the second-largest wildlife-oriented ecological continuum covering 327,000 hectares in the central west region of Burkina Faso, has experienced severe degradation, particularly due to mining activities. Therefore, it has become crucial to study the biophysical and biochemical impacts of mining effluents on land resources to mitigate their effects on the natural ecosystems and preserve biodiversity within the complex. This is particularly vital in ecologically sensitive areas such as the PONASI complex. Thus, SRTM images from the years 2011 were chosen and processed in order to highlight the contour lines of the environment, from which topographic profiles were drawn in order to determine the direction of the propagation of mining pollutants from the top of the slopes to the level of the lowlands. Also, Landsat satellite images from the years 2022 were processed in order to highlight the land cover units. The combination of these images made it possible to judiciously identify soil sampling sites. A total of 23 soil samples were taken, packaged in indelible bags and transported to the laboratory of the Bureau of Mines and Geology (BUMIGEB), for chemical analyses, in order to determine the levels of cyanide and mercury contained in the soils, and to study their impacts on soil fertility in the research area. The results reveal that soil degradation related to mining activities around the complex. Indeed, the analysis of soil samples in the laboratory revealed the presence of cyanide and mercury at mining sites at values higher than the WHO standard in Burkina Faso, for soil lethality to these heavy metals (<0.5mg/Kg for cyanide, and <50mg/Kg for mercury) in places. These mining pollutants used in the gold extraction process spread through the environment, leading to a reduction in soil organic matter, a decrease in the sums of exchangeable bases, a variation in hydrogen potential (PH) and a loss of soil fertility. In addition, the tracing of the toposequences crossing the mining sites have made it possible to identify the risks of runoff of these mining pollutants in the overall environment of the complex according to the topography, which could contaminate all the ecological entities of this protected area and thus degrade its biodiversity. Therefore, protective actions must be taken to ensure the conservation of biodiversity within the ecological complex.