What about birds and animals that rely on alien trees for a home?

Stands of alien plants do sometimes provide a habitat for birds or animals. Examples include birds that nest in large trees, or alien grey squirrels. However, it is true that many more species are displaced by alien plant invasions that are benefited by them, and many of these are rare or endemic species. The few species that find a home in alien plant stands were often not originally found there and are not considered as priorities for conservation.

List of Declared Invader Species

Working for Water Programme

Won’t bio control agents attack our indigenous plants?

No. Before bio control agents are considered for release, they are subject to a period in quarantine. During this time, they are carefully screened to ensure that they will attack only the target alien plant species, and that they can complete their life cycles and reproduce only on the target plant species. Any bio control agents that is in any way capable of damaging indigenous plants or important crafts will not be released.

What about erosion after clearing alien plants?

There is concerned that clearing operations will result in excessive erosion if sites cannot be effectively rehabilitated. This concern is receiving attention by researching available methods of rehabilitation. It is also true, though, that invasion of catchments areas by alien plant can result in serious erosion following the inevitable fires that occur from time to time, rendering the soil more susceptible to erosion as a result of their high intensity. Thus failure to clear will also have detrimental effects.

Can we really afford to spend large sums of money on clearing alien plants?

All of the economic studies done to date indicate that clearing operations are cost effective in terms of water savings. In most studies, this conclusion has been reached without even considering the additional benefits for catchments stability, biodiversity, and job creation. Studies also show that clearing as soon as possible is far more efficient in economic terms than leaving the problem to be dealt with later. Given the significant impacts predicted, the question would be better phrased in terms of whether we afford not to clear!

Are the herbicides used in alien plant control environmentally friendly?

Only herbicides registered in terms of the Fertilisers, Farm Feeds, Agricultural Remedies and Stock Remedies Act (Act 36 of 1947) are used to control alien plants. Before they can be registered for use, all herbicides have to comply with stringent environmental and health standards relevant to South African conditions. In addition, most of these herbicides were developed overseas and are used by developed countries, which set very high standards for their herbicides. Therefore all registered herbicides are environmentally friendly, provided that they are used according to the guidelines provided by the manufacturer.

What kinds of plants are regarded as a threat?

In South Africa, most concern is around invading trees because of their impacts on water. However, several species aquatic plants, succulents such as cacti, and herbaceous species are also important weeds.

Is forestry the main culprit in spreading invading alien plants?

Commercial forestry is not the main source of invasive trees. Trees that are utilized by forestry account for only 30 % of the estimated invaded area in the country, and many of these invasions are as a result of activities other than forestry. The fact that forestry uses invasive trees for the production of timber-coupled with the disturbance which forestry brings to remote areas-are non the less cause for concern and the problem needs to be managed carefully.

Are we sure we are doing the right thing by clearing large areas?

A responsible approach to environmental management demands that we act on the best available information. Indications that are the impacts of invading alien plants are significant enough to warrant large-scale clearing operations, even if their success is not always guaranteed. We cannot afford to wait until effective rehabilitation methods are developed before we deal with all situations as the impacts grow daily as alien plants spread, and the problem will soon reach unaffordable, as well as irreversible, proportions.

Should we clear plants that provide some form of benefit?

This is often a difficult question to answer. Where invading alien plants provide benefits in the form of firewood or food for humans, or fodder for animals, there is always an argument for retaining them in the landscape. However, we should assess these benefits critically against the costs, and base our decisions on the results – if the costs are greater that the benefits the clearing can be justified. Also, if woodlots or plantations (for example) are responsibly managed to prevent spread, they can be retained.

How can I help?

If you are a landowner, you should take responsibility for the problem on your own land. Establish which invading alien plants occur on your land and the options you have to bring them under control. Provincial Conservation Departments, or the local offices of the Departments of Water Affairs and Forestry, or the Department of Agriculture can be contacted for advice. Non-landowners can join one of the many volunteer groups that meet regularly to clear alien plants from public land.