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Vegetation dynamics is a proxy indicator for environmental changes. The spatial and temporal evolution of the satellite derived normalized difference vegetation index (NDVI) is a useful tool to identify environmental risk at large spatial scales. This study aimed to find the vegetation dynamics, land use and ecological risk in Nepal. The NDVI from different satellite products, land use land cover (LULC) change, human footprint pressure (HFP) and climate (i.e., temperature and precipitation) were analysed. The result showed that NDVI has significantly increased with greening in large areas. Spatially, the decreased NDVI was more noticeable in the Trans-Himalayan region. Meanwhile, the spatially averaged temperature has significantly increased at the rate of 0.03°C yr-1 and precipitation decreased by 3.94 mm yr-1 during 1982–2015. The rapid change in climate, land uses and vegetation can alter the ecosystem. The lower temperature in the mountains is a limiting factor for vegetation. Meanwhile, the high temperature in Terai and low precipitation in western and far western regions with lower VCI enhance dryness. Thus, these regions are ecologically fragile. This study of vegetation dynamics, land use, climates and HFP indicates the level of ecological risk in Nepal.
Drought is a complex phenomenon with a long-lasting global impact on human society and natural ecosystems suggesting the need for greater attention to its underlaying causes. Here, we evaluated drought conditions in ESK (Ethiopia, Somalia and Kenya) countries of East Africa during 1964–2015. We evaluate the severe droughts that occurred during 1973–1974, 1984–1985 and 2010–2011 in ESK, based on the drought severity levels. Results show that the drought characteristic parameters of drought duration and intensity increase over time, but drought frequency does not. Higher spatial drought trends were observed in large areas of the ESK countries with mean trend values of 0.0064, 0.0028, 0.00064 and -0.00095 yr–1 for SPEI-1, SPEI-3, SPEI-6 and SPEI-12, respectively. The total land area of the ESK under drought was 38–43, 46–80 and 25–46 per cent during 1973–1974, 1984–1985 and 2010–2011, respectively. Dire drought impacts have affected northeastern and southern Ethiopia, eastern Somalia and northeastern Kenya during the drought years. The spatial drought pattern analysis suggests an increase in drought in vulnerable areas which calls for better drought management strategies to reduce the risks on the natural and human systems.
The Lancang-Mekong River Basin (LMRB) is Asia's most important transboundary river. The precipitation-dependent agriculture and the world's largest inland fishery in the basin feed more than 70 million people. Floods are the main natural disasters which pose a serious threat to the local agriculture and human life. In the future, climate change will affect the streamflow and lead to changes in flood events. Based on the GMDF and GCM data, the SPI and the VIC model were used to assess the impact of climate change on streamflow and flood events during the historical (1985–2016) and future periods (2020–2050) in the LMRB. The results show that the LMRB will become more humid in the future and annual precipitation will change from about -2 to 6 per cent under RCP4.5 and RCP8.5. In the future, this basin should experience a higher flood risk, with more flood events and a relative increase in the flood peak and frequency reaching up to +15 and +58 per cent, respectively. This study contributes to improve our understanding of the role of climate change on streamflow and flood events and provides a scientific reference for the development of local water resources management in the LMRB.
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