The Economic Implications of Robinia pseudoacacia L. (black locust) on Agricultural Production in South Africa

ABSTRACT

Robinia pseudoacacia L. (black locust) is an invasive deciduous, broad-leaved tree that has the potential to be widely distributed across South Africa. It has invaded all nine South African provinces. The potential economic impact of R. pseudoacacia on agricultural production stems from the tree’s ability to reduce the carrying capacity for livestock. This study estimated the potential economic implications of R. pseudoacacia on agricultural production in South Africa, specifically the livestock sector. R. pseudoacacia’s potential distribution was calculated by using a maximum-entropy predictive habitat model, MaxEnt. The distribution of livestock, based on grazing capacity (ha/large stock unit) in South Africa, was then determined. The potential direct economic impacts were estimated by assessing the impact of the potential distribution of R. pseudoacacia on the carrying capacity for livestock. The results showed that an infestation of R. pseudoacacia has the potential to reduce the total gross margin in the livestock sector by between approximately R135 million and R674 million, dependent on the level of invasion. The potential levels of foregone income and business activity found in this study reaffirm the need to devote resources to develop a viable, economical and effective control.

KEYWORDS:

• Invasive alien plants
• livestock
• grazing capacity
• MaxEnt
• economic impact

JEL CLASSIFICATION:

• Q15
• Q51
• Q57

Acknowledgements

The South African Working for Water (WfW) Programme of the Department of Environmental Affairs: National Resource Management is acknowledged for providing funding. The South African Research Chairs Initiative of the Department of Science and Technology and the National Research Foundation of South Africa also provided funding for this work. Any opinion, finding, conclusion or recommendation expressed in this material is that of the authors and the NRF does not accept any liability in this regard.

ORCID

Gavin Fraser http://orcid.org/0000-0002-6560-6455

Grant Martin http://orcid.org/0000-0001-9302-1369

Notes

1. The potential distribution of R. pseudoacacia was ranked by MaxEnt on a scale from 1 to 7 (Figure 3). Higher probability (values closer to 7) represents areas most suitable for R. pseudoacacia, while zero or lower probability indicates areas less suitable for R. pseudoacacia.

2. Other economic impacts of invasions, which were not included in this study, are lowering yield and quality of forage, increasing costs of managing and producing livestock, foregone livestock sales and potential decreases in land values (Ditomaso, 2000).

3. For more information on the classification of livestock, see Soji et al. (2015).