Drought history and vegetation response in the Angolan Highlands

Drought negatively impacts health systems, agriculture, economies, energy, and the natural environment. The vulnerability of the Angolan Highlands rural communities that are dependent on rain-fed agriculture is a concern due to the prospect of climate change and the trajectory of increasing frequency of droughts in the region. The Angolan Highlands is an essential source water region for the Okavango Delta, and southern Africa more broadly. This study integrates Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) and vegetation indices from moderate resolution imaging spectroradiometer (MODIS) in the first historical assessment of drought in the Angolan Highlands. Using the standardized precipitation index (SPI), eight distinct drought periods were identified: 1981-1982, 1989-1990, 1994, 1995-1997, 1999-2000, 2014-2016, 2017-2018, and 2018-2020, with the frequency of drought increasing since 1981. The relationship between drought occurrence and El Nino Southern Oscillation (ENSO) is not linear; with two of the eight drought periods occurred exclusively during El Nino years. The seasonality of precipitation, MODIS enhanced vegetation index (EVI), and normalized difference vegetation index (NDVI) are similar, with NDVI and EVI being lowest at the end of the dry winter months (August), and highest during the summer rainfall season. The strong relationship between precipitation and vegetation, anthropogenic pressure on the landscape, and increased drought occurrence are likely to lead to potential environmental degradation in future. Mitigation and adaptation strategies to drought may be required, especially concerning water resources and agricultural practices within the Angolan Highlands region.

Automated summary

Drought has detrimental effects on health systems, agriculture, economies, energy, and the natural environment. The vulnerability of rural communities in the Angolan Highlands, which rely on rain-fed agriculture, is a concern due to the increasing frequency of droughts and the potential impact of climate change. This study conducted the first historical assessment of drought in the Angolan Highlands, using climate data and vegetation indices. The findings indicate that droughts have become more frequent since 1981, with eight distinct drought periods identified. The relationship between drought occurrence and El Nino Southern Oscillation (ENSO) is not linear. The study highlights the need for mitigation and adaptation strategies to address the potential environmental degradation and water resource and agricultural challenges in the region.