The Albany suurveld is vulnerable to invasion by a number of alien trees and shrubs that are classified as environmental weeds.
The principal offenders are: long-leaved wattle, silky hakea, bugweed, and lantana, as well as black wattle, cluster pine, Aleppo pine, and a range of gum species.
The Albany suurveld is vulnerable to invasion by a number of alien trees and shrubs that are classified as environmental weeds.
The principal offenders are: long-leaved wattle, silky hakea, bugweed, and lantana, as well as black wattle, cluster pine, Aleppo pine, and a range of gum species.
All of these species are declared weeds and invaders in terms of the Conservation of Agricultural Resources Act (CARA).
The first four that are mentioned are listed as category 1 plants (absolute nonos) and the remainder are
category 2 plants (only in demarcated areas).
In terms of the Act, land users must control category 1 plants that occur anywhere on their property and no one may propagate, distribute or establish populations of these plants.
The same applies to category 2 plants growing within 30m of floodlines or watercourses or wetlands, and those occurring outside of legally demarcated areas such as forestry plantations and nurseries.
Clearing invasive trees is very expensive. The elimination of a dense stand of black wattle trees, which resprout after clearing, may cost up to R8 000 per hectare for the initial clear, and there are further costs for the follow up operations required to get this species under control.
But the negative impacts of alien invasives are enormous, especially in a water scarce area. Studies show that the reduction in runoff caused by alien infestation in the Albany catchment area amounts to 7.23 million cubic metres per annum.
To deal with this problem, the Albany Working for Water (WfW) Project, implemented by the Gamtoos Irrigation Board, became operational in the Makana Municipality in 1998.
It is administered by the Natural Resource Management Programmes (NRMP) of the Department of Water Affairs (DWA) which forms part of DWA’s contribution to the Expanded Public Works Programme (EPWP) aimed at alleviating poverty by providing additional work opportunities coupled with skills training.
Since its inception, the Albany WfW project has spent approximately R35-million clearing more than 8 000 hectares of alien invasive plants in the Albany suurveld.
The project is focused on the catchments that yield water for Grahamstown, mainly in the Howison’s Poort area. Certain aliens are easier to clear than others and each species requires a different clearing approach, as determined by its biology.
Cluster pine and silky hakea do not sprout after cutting and store their seeds in cones. After these trees are felled, their seeds are released from the cones, and then germinate.
Then what is needed is a controlled burn to kill the seedlings before they, in turn, mature and start producing seed.
But this same fire may stimulate the germination of wattles, which store their hardy seeds in the soil. So the removal of these species takes considerable effort and commitment, but is definitely worthwhile in the long-term in ensuring that thickets of wattle do not replace stands of pine and hakea.
The golden rule for any land manager is to keep uninvaded areas clear of any invasive plants. This can be done at a relatively low cost but the gains for veld condition, fire management and water yield are massive.
Ultimately, timely removals, aimed at weeding out those individuals escaping from denser stands, will increase the value of property and ensure a sustainable enterprise on the land. In order to prioritise clearing operations, the WFW programme assesses water catchments and their degree of alien infestation.
This results in a listing of priority areas. But this does not mean that invasive plants on non-prioritised land should be ignored.
It is in the interest of landowners to do their own land assessment and to prioritise those areas that are important for water yield, grazing or any other factors that may influence the sustainability of their production.
Given the enormity of the problem of invasive aliens, the long-term solution lies in biological control. True to its name, biocontrol does not necessarily seek to eradicate a problem species, but aims to reduce invasive populations to a manageable level or ‘nuisance status’.
Rigorous testing and the use of agents (such as insects) which are specific to the target plant have meant that risk assessments across the world show biocontrol to be an ecologically safe method.
Essentially it involves the testing of an imported agent (a seed-eating insect or pathogenic fungus) that is associated with the invasive plant and no other in its home territory.
After meticulous testing to ensure that only the target plant is attacked, the agents are then made available for distribution.
Fortunately for landowners, effective biocontrol agents are available for a number of invasives, including long-leaved wattle, black wattle, and silky hakea.
However, it will take several generations for biocontrol agents to reduce aliens to nuisance status. In the meantime, mechanical clearing remains the best option.
Landowners as custodians of the land for future generations need to take responsibility and start clearing aliens as prescribed by law.
Only when landowners, municipalities, government and private institutions all work together on the alien
invasive problem will the programme have a reasonable chance of success.
For further information and advice, landowners can contact Jonathan Pryor in the Albany office of Working for Water (WfW) Programme on 046 636 1449 or 072 507 8919.
