Effects of soil and water conservation on vegetation cover: a remote sensing based study in the Middle Suluh River Basin, northern Ethiopia

Abstract

Background: Soil and water conservation (SWC) has been implemented in the Tigray Region of Ethiopia since 1985. Besides this, the agricultural development strategy of the region which was derived from the national agricultural development led industrialization strategy formulated in 1993 was focused on natural resources rehabilitation and conservations. Accordingly, each year a 20-days free labor work on SWC activities were contributed by the rural communities. Other programmes such as productive safety net programmes, and sustainable land management project were deploying their resources aiming to reverse the degraded landscape in the region. Method: Multi-temporal remote sensing data of landsat imageries were used for estimating the normalized difference vegetation index, soil adjusted vegetation index (SAVI) and land surface temperature (LST) for the years 1985, 2000 and 2015. Long-term station based data on daily precipitation started from 1973 was aggregated to derive average annual precipitation (AAP) into three sections to correspond with the processed image data. The precipitation data then converted into raster format using the inverse distance weight interpolation method. The analysis was done using ENVI 5.3 software and results were mapped in ArcGIS 10.3 package. The correlation between AAP and SAVI; LST and SAVI was evaluated on village polygon based as well as pixel-by-pixel. Results: The results based on village polygons show that there is statistical significant inverse relationship between SAVI and LST in all the study periods. The correlations between AAP and SAVI pixel-by-pixel were r = − 0.14 in 2015 and r = 0.06, r = 0.25 for 2000 and 1985 respectively. In 1985, the total area with SAVI ≥ 0.2 was 23.57 km2. After 15 years (from 1985 to 2000), the total area with SAVI ≥ 0.2 increased to 64.94 km2. In 2015, the total area of SAVI with values ≥ 0.2 reached 67.11 km2, which is a 3.3% increment from year 2000. Conclusion: Based on the field observation and the remote sensing analysis results, noticeable gain in vegetation cover improvement have been observed in the 30 years period. These improvements are attributable to the implementation of integrated SWC measures particularly in areas where exclosure areas were defined and protected by the local community. Therefore, this study concludes by providing a theoretical bases and an indicator data support for further research on vegetation restoration for the entire region.