No abstract

Soil salinity is a major issue causing land degradation in coastal areas. In this study, we assessed the land use and soil salinity changes in Djilor district (Senegal) using remote sensing and field data. We performed land use land cover changes for the years 1984, 1994, 2007, and 2017. Electrical conductivity was measured from 300 soil samples collected at the study area; this, together with elevation, distance to river, Normalized Difference Vegetation Index (NDVI), Salinity Index (SI), and Soil-Adjusted Vegetation Index (SAVI), was used to build the salinity model using a multiple regression analysis. Supervised classification and intensity analysis were applied to determine the annual change area and the variation of gains and losses. The results showed that croplands recorded the highest gain (17%) throughout the period 1984–2017, while forest recorded 3%. The fastest annual area of change occurred during the period 1984–1994. The salinity model showed a high potential for mapping saline areas (R2 = 0.73 and RMSE = 0.68). Regarding salinity change, the slightly saline areas (2 < EC < 4 dS/m) increased by 42% whereas highly saline (EC > 8 dS/m) and moderately saline (4 < EC < 8 dS/m) areas decreased by 23% and 26%, respectively, in 2017. Additionally, the increasing salt content is less dominant in vegetated areas compared with non-vegetated areas. Nonetheless, the highly concentrated salty areas can be restored using salt-resistant plants (e.g., Eucalyptus sp., Tamarix sp.). This study gives more insights on land use planning and salinity management for improving farmers’ resilience in coastal regions.

While most studies of community forests in Senegal address issues in institutional and political arrangements for managing forests, this study was carried out to find out how these political and institutional changes embodied in the new approach to forest management impact on land use and land cover change in the country. Using the Missirah Forest in southeastern Senegal, as a case study, the objective was to quantify the land use and land cover changes that have happened over a twenty four-year period, from 1990 to 2014 using remote sensing. Six land use and land cover types were identified and mapped, namely, gallery forest, tree savanna, shrub savanna, degraded shrub savanna, croplands and settlements. The area of croplands and settlements expanded between 1990 and 2014. The conversion from natural vegetation to croplands (14.45%) was higher than the conversion from cropland to natural vegetation (3%). Between 1990 and 2003, the expansion in croplands was higher than between 1990 and 2003 but the reverse was the case for settlements. Regarding vegetation types, they decreased in cover between the two periods with the exception of shrub savanna that experienced an increase of 1.46% from 1990 to 2003. Transition to less wooded vegetation (31.58%) was higher than transition to more wooded vegetation (13.91%). This study shows that deforestation and forest degradation are still in progress despite the implementation of a management plan for a full rotation.

Knowledge on deforestation and forest degradation (DFD) in managed forest is widely available. However, the way local people perceive DFD and its drivers are not well understood. This study aimed at assessing local perception of vegetation dynamics and factors driving DFD in a community-managed forest. Data were collected by means of interviews conducted with 136 respondents from 5 communities. Non-parametric tests were used to analyze the data. The results show that 67% of respondents perceived DFD to be occurring in the forest. The perception of the level of forest degradation among the age groups in the communities was significantly related. The tree species cited as declining were those used for fuelwood and food as well as (Sterculia setigera Delile and Parkia biglobosa Jacq. R. Br. ex G. Don) and species of high timber value (Pterocarpus erinaceus Poir and Cordyla pinnata Lepr. ex A. Rich). An overlapping was found between local estimate of species decline and those found to be decreasing with vegetation inventory confirming the reliability of local knowledge. Charcoal production, bush fire, seasonal migration of cattle, and illegal logging, were identified as the main drivers of vegetation dynamics by more than 50% of the respondents. Main economic activities and community location significantly affected the ranking of the perceived drivers of vegetation dynamics, while age group did not.