Impacts of mining activities on land cover and forest stock in Mbozi district, Mbeya region, Tanzania

A study was conducted in three villages of Nanyala ward in Mbozi District to assess the impact of mining activities on land cover and forest stock. Landsat images of 1991, 2000 and 2011 were used to assess the trend of land cover changes. The Forest was stratified into mined and un-mined forest area. A concentric circular shaped sample plot with sampling intensity of 0.19 % was used. 70 sample plots were laid and measurements were taken for estimation of stocking, basal area, volume and tree species diversity. Structured and semi structured questionnaire were administered to randomly selected 90 households in three villages adjacent to the mining area. Spatial data was analyzed by Arc View GIS version 9.3 and ERDAS Imagine version 3.2.and MS Excel was used to analyze N/ha, G and V, while Shannon Wiener Index of Diversity data was analyzed using PAST. ANOVA was used to determine the significant different of forest parameters at p<0.05. Quantitative Social economic data were analyzed using SPSS version 16. The results of land cover derived from landsat images from 1991 to 2011 shows the increase of mining area from 0.77 ha to 517.44 ha and bush land from 397.91 ha to 807.61 ha, while forest area decreased from 567.55 ha to 0.77ha. Average number of stems per hectare in un-mined area was 151.31 ±31 (SE) N/ha and in mined area 25.01± 6.276 (SE) N/ha, mean basal area for un-mined forest area was 2.50 ± 0.26 (SE) m2/ha and in mined forest area was 0.21 m2/ha. The mean volume for un-mined area was 9.61 ± 0.19m3/ ha and 0.51 ± 1.18 m3/ha for mined forest area. Shannon Wiener Index of Diversity shows more species in un-mined forest than mined forest 1.29 ± 0.63 (SE) and 0.36 ± 0.08 (SE) respectively. The finding shows that the drivers of land cover changes are mining activities which accounted for 50 %, charcoal burning 27.8 %, uncontrolled bush fires 11.1 %, fire wood 6.7 % and 4.4 % crop cultivation. Comparatively, limestone processing signifies to have more effects to the environment than granite extraction. The study recommends conducting environmental auditing and mitigation studies against these damages including regular inspections should be executed to keep these activities of mining under control as stipulated in Environmental Management Act No 20 of 2004.

District Executive Director for Mbozi District Council