Arid Land Research Center, Tottori University, 1390 Hamasaka, Tottori 680-0001, Japan; Department of Land Resources Management and Environmental Protection, Mekelle University, P.O. Box 231, Mekelle, Ethiopia.
Arid Land Research Center, Tottori University, 1390 Hamasaka, Tottori 680-0001, Japan.
Sci Total Environ. 2020 Feb 10;703:135016. doi: 10.1016/j.scitotenv.2019.135016. Epub 2019 Nov 3.
Land degradation by water and wind erosion is a serious problem worldwide. Despite the significant amount of research on this topic, quantifying these processes at large- or regional-scale remains difficult. Furthermore, very few studies provide integrated assessments of land susceptibility to both water and wind erosion. Therefore, this study investigated the spatial patterns of water and wind erosion risks, first separately and then combined, in the drought-prone region of East Africa using the best available datasets. As to water erosion, we adopted the spatially distributed version of the Revised Universal Soil Loss Equation and compared our estimates with plot-scale measurements and watershed sediment yield (SY) data. The order of magnitude of our soil loss estimates by water erosion is within the range of measured plot-scale data. Moreover, despite the fact that SY integrates different soil erosion and sediment deposition processes within watersheds, we observed a strong correlation of SY with our estimated soil loss rates (r = 0.4). For wind erosion, we developed a wind erosion index by integrating five relevant factors using fuzzy logic technique. We compared this index with estimates of the frequency of dust storms, derived from long-term Sea-Viewing Wide Field-of-View Sensor Level-3 daily data. This comparison revealed an overall accuracy of 70%. According to our estimates, mean annual gross soil loss by water erosion amounts to 4 billion t, with a mean soil loss rate of 6.3 t ha yr, of which ca. 50% was found to originate in Ethiopia. In terms of land cover, ca. 50% of the soil loss by water erosion originates from cropland (with a mean soil loss rate of 18.4 t ha yr), which covers ca. 15% of the total area in the study region. Model results showed that nearly 10% of the East Africa region is subject to moderate or elevated water erosion risks (>10 t ha yr). With respect to wind erosion, we estimated that around 25% of the study area is experiencing moderate or elevated wind erosion risks (equivalent to a frequency of dust storms >45 days yr), of which Sudan and Somalia (which are dominated by bare/sparse vegetation cover) have the largest share (ca. 90%). In total, an estimated 8 million ha is exposed to moderate or elevated risks of soil erosion by both water and wind. The results of this study provide new insights on the spatial patterns of water and wind erosion risks in East Africa and can be used to prioritize areas where further investigations are needed and where remedial actions should be implemented.
水和风的侵蚀导致土地退化是一个全球性的严重问题。尽管针对这一主题进行了大量研究，但在大尺度或区域尺度上量化这些过程仍然具有挑战性。此外，很少有研究综合评估土地对水和风侵蚀的易感性。因此，本研究使用最佳可用数据集，分别调查了东非干旱地区水和风侵蚀风险的空间格局，然后综合调查了这些风险。至于水侵蚀，我们采用了修正后的通用土壤流失方程的空间分布版本，并将我们的估计值与斑块尺度测量和流域泥沙产量（SY）数据进行了比较。我们通过水蚀估算的土壤流失量的数量级在测量的斑块尺度数据范围内。此外，尽管 SY 整合了流域内不同的土壤侵蚀和泥沙沉积过程，但我们观察到 SY 与我们估计的土壤流失率之间存在很强的相关性（r=0.4）。对于风蚀，我们使用模糊逻辑技术整合了五个相关因素，开发了一个风蚀指数。我们将此指数与来自长期 Sea-Viewing Wide Field-of-View Sensor Level-3 每日数据的尘暴频率估算值进行了比较。这一比较显示了 70%的总体准确性。根据我们的估计，东非地区每年的水蚀总土壤流失量约为 40 亿吨，土壤流失率平均为 6.3 t ha yr，其中约 50%来自埃塞俄比亚。就土地覆盖而言，约 50%的水蚀土壤流失来自耕地（土壤流失率为 18.4 t ha yr），占研究区域总面积的 15%左右。模型结果表明，东非地区近 10%的地区面临中度或高度的水蚀风险（>10 t ha yr）。至于风蚀，我们估计研究区约 25%的地区面临中度或高度的风蚀风险（相当于尘暴频率>45 天 yr），其中苏丹和索马里（以裸露/稀疏植被覆盖为主）的比例最大（约 90%）。总的来说，约有 800 万公顷的土地面临水和风侵蚀的中度或高度风险。本研究的结果提供了东非地区水和风侵蚀风险空间格局的新见解，可用于优先考虑需要进一步调查和实施补救措施的地区。
