The impact of seasonal variability of rainfall and drought on vegetation and livestock population in Central District, eastern Botswana

Background

This research aimed to elucidate the components of rainfall variation, their influence on the natural vegetation growing season and consequent impacts on the livestock population.

Methods

This study evaluates the influence of rainfall metrics and drought on vegetation and livestock in Central District, Botswana. It uses Pearson correlation analysis to assess the relationships between rainfall metrics, drought, vegetation and livestock. Trends were analysed using Mann–Kendal and Sen's slope analysis.

Results

It was found that rainfall variability and drought frequently occur in Central District, with continuing effects on vegetation and livestock. From 1990 to 2020, the district experienced moderate droughts on cycles of approximately alternating years. Severe drought occurred in 2003, and 2000 was a wet year. No significant trend was observed in rainfall metrics. The normalised difference vegetation index (NDVI), and the number of cattle and goats significantly declined. Annual NDVI shows a significant relationship with the number of rainy days, drought and consecutive wet days; cattle numbers are negatively correlated with consecutive dry days. Seasonal results show that NDVI is highly correlated to the number of rainy days in April–June (AMJ) and October–December, and NDVI is correlated to the standardised precipitation evapotranspiration index (SPEI) during AMJ and July–September.

Conclusions

The study findings revealed a seasonal and annual relationship between rainfall metrics, SPEI 12, livestock (goats, sheep and cattle population) and NDVI in the Central District of Botswana.