Cape Town to act against invasive alien vegetation

It would cost R4 billion to bring under control by 2020 all the invasive alien species that are having a devastating impact on the Western Cape's unique natural heritage, say environmentalists.

Conservation managers responsible for protecting the province's rich biodiversity are "boxing clever" by devising strategies that would prove most effective within budgetary and staffing constraints.

And they will be significantly assisted when regulations promulgated under the National Environmental Management Biodiversity Act (Nemba) are published - hopefully next month - that will give authorities legal power to enforce control measures for listed alien species.

Invasive alien plants are currently the responsibility of the national agriculture department, operating in terms of the Cara (Conservation of Agricultural Resources Act) regulations.

But the department has just one official dealing with all Cara complaints in the Peninsula and Overberg, and it could take months to deal with just one property owner.

But when the new biodiversity regulations were published, municipalities like the City of Cape Town could be declared "competent authorities" to deal with the problem of listed alien species, said Louise Stafford, co-ordinator of the city's relatively new Invasive Alien Species Unit.

Plants listed in Category 1a of Nemba, and which must be eradicated, include on the Peninsula several Australian acacias like the screw pod wattle, kangaroo wattle and the hop wattle, as well as sweet hakea and tickweed.

In the Overstrand, it includes the New Zealand Christmas tree - ironically, a species planted as street trees by the city.

But Stafford, who joined the city from CapeNature in February 2008 and who now heads a small but dedicated staff of five, points out that an equally important part of their job is to prevent species from becoming established by detecting and removing them at an early stage.

On the Peninsula, such plants (Category 1b) include the "tree of heaven" (Ailanthus altissima), pampas grass, Cotoneaster and Spanish broom.

Stafford explained that the mandates of several departments in the city currently included some aspect of invasive alien species control - for example, the fire department because of the fire hazard posed by alien trees, and the health department because of the health risk from the exotic house crow.

But none of the many policies and by-laws focused specifically on invasive species.

"Currently, various departments are involved in managing invasive plants in their areas of responsibility, and my unit is playing a co-ordinating and supporting role," she explained.

A legal and policy framework on invasive alien species for the city had just been completed.

The next step was to develop an invasive species policy that would align the city with Nemba and its regulations.

A draft of the policy would be released for public comment - a compulsory step because it would be applicable to all landowners.

"We hope to have the policy ready for comment by the end of the year," said Stafford.

"It will provide the city with a blueprint for how to manage its invasive species in a cost-effective sustainable manner, because the way we're doing it now is not really sustainable.

"We're mostly reactive, and the policy changes the emphasis to being proactive.

"The first line of defence in managing invasives effectively is preventing potential risky species from entering the borders of the country.

"Detecting invasives that enter unseen is the second line of defence.

These two important management options are more cost-effective and therefore an investment, because your return is the saving that you make in the long term."

The removal of alien species - both flora and fauna - is a topic that gets many people upset.

Some people still refer rudely to the "tree Taliban", for example, while others get extremely emotional when mallard ducks, proved to interbreed with indigenous ducks all over the world, are removed to protect local species like the yellow-billed duck.

But Stafford said the message they were trying to get out was that invasive alien species control was not about indiscriminately removing plants or animals.

"That's not why we do it. It's because of the very real threats that these invasives pose to our indigenous species and because of their impacts on ecosystem functioning."