Assessing impact of Soil and Assessing Impact of Soil and Water Conservation Measures Oo Vegetation Cover in Burkina Faso using MODIS NDVI Data

Abstract

Following the decades of dramatic droughts that started in the 1960s, Burkina Faso started implementing Soil and Water Conservation in 1960s (SWC) measures to combat desertification. The implementation of SWC measures influences the changes in vegetation, and can be seen Normalized Difference Vegetation Index (NDVI) obtained from satellite images. It is therefore important to assess vegetation changes in SWC sites to assess vegetation growth especially in areas where the natural vegetation is degraded by climate change. Therefore, this study assesses the vegetation dynamics in (SWC) and non SWC areas in Burkina Faso using Moderate Resolution Imaging Spectrometer (MODIS) NDVI data. MODIS NDVI 250 m data was used to assess the vegetation trends, in SWC and non SWC sites. Also, NDVI trends from 2002 to 2016 were detected using the Man-Kendall test to explore the spatial and temporal variations over the entire Burkina Faso and some Region of Interest (ROI). The Break for Additive Seasonal Trend (BFAST) method was used to estimate the vegetation changes in both SWC and non SWC sites. Finally, the Residual Trend (RESTREND) analysis was used to determine the vegetation growth of SWC sites devoid of rainfall and temperature as explanatory variables. The vegetation activity shows a distinctive positive trend between the period of study particularly in the Sahel and Sudan-Sahel climatic zones. On the average, NDVI increased by 4.4x10^-6 annually from 2002 to 2016. Majority of the SWC sites experienced increasing (greening) trends, whiles the non SWC sites showed negative (browning) trends. There are sudden changes in vegetation trends at both SWC and non SWC sites which might be caused by fires, drought and other human activities influencing the vegetation. SWC measures have major impacts on phenological changes in NDVI and the response of vegetation phenology to SWC measures varies across different climatic zones. The results from the RESTREND showed that vegetation trends in all the SWC stations experienced an increase in vegetation growth and the non-SWC analyzed stations have experienced decline in vegetation trends during 2002 to 2016. Areas experiencing decrease in vegetation change could be identified as hot spots for land degradation, where government and policy makers could easily implement SWC measures to reverse the situation