Abstract:
The invasive Prosopis spp. tree is one of the major causes of disturbance affecting the Orange River
water management areas in the Northern Cape, South Africa. These disturbances affect natural
capital, such as reducing the stream flow of the Orange River, causing a decline in biodiversity of
the native Nama Karoo vegetation, consuming excessive water, and invading dryland areas.
Therefore, we assessed the economic value of different land-use options following the control of
Prosopis spp. to prevent re-invasion using a system dynamics model. This study yields positive
cumulative NPVs of between ZAR28.3 million and ZAR98.3 billion when co-finance of between 20%
and 100% is included to clear the Prosopis spp., combined with the productive land use of the cleared
land by the private sector. This is in stark contrast to a negative NPV of -ZAR11.6 million when no
alternative land-use activity is implemented on the cleared land. This study shows empirically that
clearing Prosopis spp. and restoring the cleared land for agricultural land-use options is a costeffective
strategy for controlling the invasive Prosopis spp. trees.
