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Abstract
In 2020, nearly 400 elephants died within the Okavango Delta region in Botswana, creating the worst-ever elephant mass die-off event in history. This catastrophic event was widely blamed, although not scientifically proven, on toxic cyanobacterial blooms. However, it did not explain why we saw this increase in cyanobacteria in 2020. We conducted a landscape-wide time-series analysis using freely available European Space Agency’s Sentinel-2, NASA’s Landsat-8 satellite, and locally collected climate data. We used existing bio-optical models, Normalized Difference Chlorophyll Index and Green Line Height, as proxies for chlorophyll-a and phycocyanin (cyanobacteria) concentrations, as well as thirteen variables to determine the driving factors behind the increased cyanobacterial activity. We found that 2020 was an exceptional year for cyanobacteria blooms in the Okavango Delta compared to the past three years (2017–2019), precipitation (8.8%), wetlands area (7.5%), and Palmer Severity Drought Index (3.2%) being the determining drivers behind the increased cyanobacterial activity.