Written by Henrico Harris
Alien plant species are introduced, intentionally or unintentionally, to an area where they do not naturally occur. Once these species begin to spread and establish themselves beyond their initial point of introduction, they are classified as invasive alien plant (IAP) species.
IAPs are categorised into four different classifications:
Category 1:
- Most harmful species require immediate control and eradication.
- Trade and planting are strictly prohibited.
Category 2:
- It must be controlled and removed wherever possible.
- Trade and planting are strictly prohibited.
Category 3:
- Potentially invasive species require a permit for restricted activities.
- Includes commercially important species like pine, wattle, and gum trees.
Category 4:
- May remain in prescribed areas or provinces.
- Further planting, propagation, or trade is prohibited.
IAPs can result in the overuse of local water resources, indigenous biodiversity loss, reduced ecosystem services, and lower land values due to infestation. It is, therefore, a legal requirement for all landowners to manage, and it can be daunting. Effectively managing IAPs involves proactive planning and action, including area surveys, species identification, cost calculations, and sufficient actions and implementation. Creating an IAP clearing plan will provide structure, measurable actions and outcomes, training material, listing of species and clearing methods, indicating infestation rates through continuous recordkeeping, and determining follow-up visits.
Looking from a risk perspective, staff that are working with IAP clearing should have been adequately equipped with personal protective equipment (PPE), safe implements, calibrated spray equipment and provided with adequate training (such as first-aid, chainsaw operations, chemical handling, and health and safety training). Training and training records are important to ensure the correct identification before taking action, using proper removal methods, treating IAPs with the correct products and applying products effectively.
Determining the correct clearing method primarily depends on the scale of IAP infestation, location, growth and reproductive characteristics, and resources available to the landowner. The different clearing methods include the following:
- Manual control: This is the most labour-intensive and time-consuming method and is often chosen for areas with lighter infestation, younger plants, or ecologically sensitive areas, such as wetlands, riverbanks, and mountain slopes. It involves hand-pulling and bark stripping.
- Mechanical control: This method, which includes the use of heavy machinery or felling with chainsaws, is chosen for areas with large infestations and non-sprouting IAP individuals. It requires time and effort, and resprouting IAPs require herbicide application after removal.
- Chemical control: This method uses herbicides that potentially involve environmental risks, particularly in natural areas. Chemical control methods should always be cautiously used to limit adverse effects on non-target plant and animal species. They should not be considered during the rainy season as the contamination risks for non-target areas are high.
- Biological control: Biological control methods aim to introduce selected natural enemies of the IAP species’ natural distribution range to limit the plant’s ability to grow and/or reproduce. This control method is a long-term strategy that operates in parallel with other control methods.
A farm needs to ensure they have the following records available during an environmental audit:
- The farm’s IAP management plan,
- IAP management training records,
- Availability of Category 2 permits, and
- Proof of IAP management for Category 1a, 1b, and 3 will be requested.
If the auditor notes a finding regarding IAPs, the finding measure will be based on the risk evaluated during the audit. Risks are determined by assessing the implemented actions and results according to infestation rate and management results.
IAPs require constant management with regular follow-ups to prevent future infestations. With a well-thought-out and established IAP management plan, the daunting task of ensuring that IAPs stay in control becomes manageable and common practice, with risks and consequences being minimised.
To ensure you are up-to-date on IAPs, please visit your MySIZA profile under the members’ resources tab to download or read the SIZA Guide to Controlling Invasive Alien Plants. You can also contact Henrico at henrico@siza.co.za / 021 852 8184.