The influence of contrasting fire management practice on bush encroachment: Lessons from Bwabwata National Park, Namibia

Questions Bush encroachment, (i.e. disproportionate woody vegetation increase at the cost of grassland) has negative impacts for biodiversity conservation and tourism by homogenising habitat structure and decreasing grazing and game-viewing. While herbivory, rainfall, and CO2 all influence changes in woody vegetation cover, fire has the best potential for vegetation management. Changes in fire management can either encourage or suppress bush encroachment and a better understanding of how changes in fire regime affect vegetation structure is needed. Therefore, this study addressed three questions: (a) how has woody cover changed over two decades (1999-2019); (b) what is the role of land use, rainfall, and fire in influencing woody cover change; and (c) what are the management implications? Location Bwabwata National Park (BNP), Namibia. Methods The study used a novel combination of repeat ground photography and satellite-based remote-sensing products to explore the change in woody vegetation in relation to rainfall, land use, and fire seasonality. Results Woody vegetation has increased by 13% since 1999 in BNP. Change in vegetation structure differed in the east and west of the park. Early-season burns in the east of the park were associated with an increase in trees over 3 m tall consisting primarily of Dialium englerianum, Terminalia sericea and Burkea africana. Repetitive late dry-season fires in the west of the park were associated with an increase in shrubs under 3 m dominated by Baphia massaiensis and Terminalia sericea. Conclusions Both early- and late-season fires are of value in management of bush encroachment. Early dry-season fires appear to reduce the rate of bush encroachment and contribute to maintaining a heterogeneous vegetation structure. This fire management strategy reduces wildfire risk, conserves biodiversity, and promotes tourism and is, therefore, recommended for the park.