Why all the fuss about aliens?

2010-10-14 00:00

THIS week is National Weed Buster Week with a 2010 theme of “My River, My Life”. I think by now we have all heard about alien plants and other organisms, but do we all know what they are and what they do? Why so much fuss and what can we do anyway?

As we drive around town we can see the hedges and verges swamped by bugweed, for example. Sure, there are areas that have been cleared and we can see that these infested places are just neglected patches of land. They are unsightly but we can ignore them as they do not affect us directly. So we go home and enjoy our colourful and varied gardens, which we know we can control but which in fact, can be as dangerous as these neglected and weedy patches.

An alien plant does not occur here naturally, it comes from another climate, another environment, or another ecosystem. It has arrived here without all the natural limiting factors it lived with in its home environment and it found one of the most welcoming climates in the world here in South Africa. It flourished, grew unattended and started to take over, replacing the local plants and dominating the vegetation. What was once a varied yet delicately balanced mixture of a fascinating range of plants soon becomes an impenetrable mass of this single exotic alien.

In Howick or Pietermaritzburg, we are very familiar with the worst culprits such as bugweed, bramble and lantana, but we are often blissfully unaware of the other several hundred species that are not as visually prominent but can in fact pose an even more serious threat. Perhaps the most dangerous aliens are the ones that have only just started their campaign of violence. They are currently small and relatively insignificant invaders but have the real potential to become another bugweed or lantana. These are the ones we have to stop, and we have to stop them now while we still can. But which ones are they? What do they look like? What do they do and how do we stop them?

The Dusi Canoe Marathon is under severe threat from an exploding population of various alien water weeds like water hyacinth and water lettuce. The Umgeni Valley Gorge in Howick is being swamped by cat’s claw creeper and balloon vine. These are just two examples of infestations of aliens that require urgent and expert action, and controlling these water weeds in a river such as the Duzi requires very expert attention. It is easy to damage the river even further with the mass destruction of alien vegetation and wherever possible biological control techniques should be introduced and encouraged.

Many gardens have plants with juicy berries and fragrant flowers in order to attract birds and butterflies. Yet these characteristics are the same ones that can make an alien a threat, by diverting the birds and butterflies to enjoy these aliens while the less attractive indigenous plants are ignored and which then struggle to reproduce at all. Furthermore, the berries of these non-indigenous ornamentals are carried out of the garden and deposited along fence lines and under trees. Are we fully aware of which ones pose a threat, which of our sterile, hybrid ornamentals can in fact escape?

When all this is considered, how can we as individuals join this battle? What can we actually do? The answer is simple: take an interest, learn about the problems and where possible change a few things. The saying “every little helps” is particularly relevant in this context. The battle is going to be never-ending, but it is a battle we as inhabitants of this Earth simply cannot lose.

• Clive Bromilow is the author of Problem Plants and Alien Weeds of South Africa.

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