Bush encroachment and impacts on grass biomass in Senkelle Swayne’s Hartebeest Sanctuary, Ethiopia

ABSTRACT

The aim of this study was to assess bush encroachment and its impact on herbaceous biomass in Senkelle Swayne’s Hartebeest Sanctuary. Data on the extent and trend of bush encroachment were collected using Geographic Information System and Remote Sensing techniques. A total of 50 plots were used for vegetation and grass biomass data collection. A nested plot design was used to collect woody species with diameter at breast height (dbh) ≥ 10 cm, dbh > 2 cm and < 10 cm and dbh ≤ 2 cm. Within each 20 m × 50 m plot, five subplots, each 0.5 m × 0.5 m, were used to gather grass biomass data. Grass biomass was determined in the laboratory by oven drying at 65–70°C for 48 h. Data were analysed using descriptive statistics. Analysis of satellite data was done by preprocessing satellite images and enumerating a change matrix. The results showed that: (i) total area covered by grassland declined by 9.8% while the total area covered by bushland increased by 21.4% over the past 30 years; (ii)seven woody species belonging to four families were recorded in the encroached area; (iii) there was a significant difference (p < 0.05) in grass biomass between encroached and non-encroached strata; and (iv) the abundance of tree/shrub species and grass biomass were negatively correlated.

Key policy insights

• There is an urgent requirement to implement projects that focus on bush clearance and the rehabilitation of grasslands appropriate for relevant foraging species – which could increase forage quality and quantity in protected areas.

• There is a need to develop and implement systems to determine the carrying capacity of the Swayne’s Hartebeest in the Senkelle Swayne’s Hartebeest Sanctuary to minimize negative impacts of overgrazing and ensure conservation of the species.

• Conflicting interests of local communities on the grazing land call for continuous awareness of the value of biodiversity and ecosystem services in these protected areas.

KEYWORDS:

• bush encroachment
• grass biomass
• Senkelle Sanctuary
• Swayne’s Hartebeest

Acknowledgements

We thank Hawassa University Wondo Genet College of Forestry and Natural Resources for facilitating and supporting this research work. The support of the Centre for Development Research (ZEF), University of Bonn, Germany, is duly acknowledged. We also thank DAAD in-country scholarship for providing financial support. We acknowledge the logistic support of the Ethiopian Wildlife Conservation Authority and Senkelle Swayne’s Hartebeest Sanctuary.

Disclosure statement

No potential conflict of interest was reported by the authors.

Geolocation information

Ethiopia, East Africa.

Additional information

Funding

DAAD in-country scholarship gave financial support to  Ms Lello Kabeta for data collection and analysis.

Notes on contributors

Lello Kabeta

Ms Lello Kabeta was involved in the study design; conducted field work, literature review, general data collection and analysis; and also wrote the first draft of the manuscript.

Gemedo Dalle

Dr Gemedo Dalle supervised data collection and analysis, reviewed, revised and prepared the final manuscript.

Motuma Tolera

Dr Motuma Tolera gave guidance on data collection, supervised research work, conducted data analysis and reviewed the first draft.

Girma Kelboro

Dr Girma Kelboro reviewed the draft manuscript.