Takele Alexander, Lakew Haileyesus Belay, Kabite Gizachew
Ethiopian Space Science and Technology Institute, Remote Sensing Research and Development Department, Addis Ababa, Ethiopia.
Heliyon. 2022 May 29;8(6):e09589. doi: 10.1016/j.heliyon.2022.e09589. eCollection 2022 Jun.
The Ethiopian government planned afforestation programs in the past decades whereas more attention was given to tree plantation since the 2010 year. However, the effectiveness of the afforestation programs and its impacts on vegetation cover and hydrology has not been well studied. This study aims to assess the recent campaigned afforestation program and its impact on vegetation cover and hydrology in the upper Awash basin, Ethiopia. Landsat 8 images of 2013-2020 years were used to calculate the NDVI for the upper Awash basin to assess trends in vegetation greenness for the basin. Moreover, observed streamflow and precipitation datasets of the basin were collected and used for assessing the impact of the afforestation on hydrology. The study result showed decreasing NDVI values despite the afforestation programs in the upper Awash basin. This shows either afforestation rate was less than the deforestation rate or the tree plantation campaign was not effective in the basin. In addition, the campaign based tree plantation focused on the number of tree planted not on how many trees are grown. On the other hand, mean annual precipitation and streamflow were generally increased from 2013 to 2020 in the upper Awash basin. Declining NDVI values but increasing mean annual precipitation in the Awash basin indicated that the declining vegetation was attributed to anthropogenic effects. The increasing streamflow during the same time could be due to the increasing mean annual precipitation. Moreover, the decreasing vegetation cover might have contributed for the increasing streamflow through increasing surface runoff and decreasing transpiration. However, further research is required to assess the precise impacts of afforestation on vegetation cover and hydrologic processes. Generally, the study result showed that the focus of afforestation should be on tree growing than on tree plantation alone.
过去几十年里，埃塞俄比亚政府制定了造林计划，而自2010年以来，植树造林受到了更多关注。然而，造林计划的成效及其对植被覆盖和水文的影响尚未得到充分研究。本研究旨在评估埃塞俄比亚阿瓦什河上游流域近期开展的造林计划及其对植被覆盖和水文的影响。利用2013 - 2020年的陆地卫星8号图像计算阿瓦什河上游流域的归一化植被指数（NDVI），以评估该流域植被绿度的变化趋势。此外，收集了该流域的实测径流和降水数据集，用于评估造林对水文的影响。研究结果表明，尽管阿瓦什河上游流域实施了造林计划，但NDVI值仍在下降。这表明要么造林率低于毁林率，要么该流域的植树造林活动效果不佳。此外，基于活动的植树造林侧重于种植树木的数量，而非树木的生长数量。另一方面，2013年至2020年期间，阿瓦什河上游流域的年平均降水量和径流量总体上有所增加。阿瓦什河流域NDVI值下降但年平均降水量增加，这表明植被减少是人为因素造成的。同期径流量增加可能是由于年平均降水量增加。此外，植被覆盖减少可能通过增加地表径流和减少蒸腾作用导致径流量增加。然而，需要进一步研究来评估造林对植被覆盖和水文过程的确切影响。总体而言，研究结果表明，造林的重点应放在树木生长上，而不仅仅是植树。
