Agriculture

[1] [a] Based on studies in the Karoo, with vegetation largely the same as might be expected in the Central Karoo District, the average estimated loss in ecosystem services due to degradation is approximately R1 600 per hectare per year. Should the figure of R1 600 per hectare be used and multiplied by only 5% [thin infestation] for the total area of the Central Karoo [3 885 400ha] then it is a loss of ecosystem services of more than R310 million per year, increasing each year.

[b] Whether soil deteriorates due to a loss of surface cover or due to invaders, it can be expected that the loss of ecosystem services will be much the same. The ecosystem services lost in the Karoo are usually in the form of provisioning services, in the case of grazing but also groundwater.

 [i] Not much research has been done on the impact of Satansbos on groundwater in South Africa.

[ii] Research has shown that Prosopis uses up to the equivalent of 1100 mm of water per year, or about four times the rainfall of the Karoo. A Prosopis uprising uses 80% more water than, for example, Sweet Thorn [Acacia karoo] uprising due to the much higher density in terms of stems per hectare. Additional to the direct impacts of the invaders on water, soil moisture and grazing capacity, secondary monetary impacts of invaders are in the form of the loss of drought resilience. The challenge with treating dense insurgency intruders is that the treatment costs far outweigh the benefits gained if normal economic analysis is used. The long-term impacts such as climate change and greater pressure on resources must be taken into account when considering invasive control in the Karoo. 

[iii] Not much research has been done on the impact of Tamarisk on groundwater in South Africa.

It can be expected that the impact of the Satansbos and Tamarisk will be very similar to that of Prosopis as both of them have very strong root systems, so they can reach the water at greater depths. Prosopis roots can occur up to 70 m deep.

[2]  [a] In the past 3 years the following funding was utilised for alien plant invasions:

 

Funds utilised for alien plant clearing in the last 3 years
Year	Amount
2019/20	R450 000
2020/21	R2 555 000
2021/22	R3 000 000
Total	R6 005 000

 

[b]  In the following 3 years the funding allocation for alien plant invasions will be dependent on budget allocation in the 2023 and 2024 years:

 

Funds allocated  for alien plant clearing for the next 3 years
Year	Amount
2022/23	R4 600 000
2023/24	R5 060 000
2024/25	R5 566 000
Total	R15 226 000

[3]  In the past 3 years, and as planned for the next 3 years, the project will concentrate on the following areas:

• Laingsburg: for the control of Tamerisk and Prosopis in the rivers and catchment area of the Floriskraal dam which feeds the irrigation farms below the dam and in Ladismith;
• Leeu-Gamka: for the control of Prosopis in the rivers that feed the irrigation lands in the Gamka and Leeu rivers;
• Merweville: for the control of Black Wattle and Opuntia [and many other cactus species] in the catchment areas of all rivers and causing the spreading thereof downriver and infestation of riparian areas;
• Beaufort West: for the control of Opuntia [and many other cactus species] in the catchment areas of all rivers and causing the spreading thereof downriver and infestation of riparian areas; and
• Murraysburg: for the control of Solanum [Satansbos] in the catchment areas of all rivers and causing the spreading thereof downriver and infestation of riparian areas.

In summary only a very limited portion of the Central Karoo can be serviced with the available funding. In order to make a significant impact on the spreading of alien invasive plants the required funding and application of labour would need to be increased 5 fold.