Ret to River Menu  Home Menu

PAVCO menu  
Primary Alien Vegetation Control

Bugweed (Solarnum Mauratainum) one of Hout Bay's most dangerous alien threats. Classified as a noxious weed, this shrub/tree is widespread.

Press Comment

There is another significant area of activity being that of "bio control". This is the application of host-specific control agents "bugs" which are proving very effective but cannot in the foreseeable future achieve the degree of control needed on a very wide variety of noxious and invasive aliens which must be addressed.

In the main, organised alien vegetation control is usually of the second type (what could be called SAVCO) Secondary Alien Vegetation Control, i.e. where infestations have assumed significant size to warrant large scale control measures needing teams to mechanically cut the undesired weeds and if necessary poison the stumps in the case of shrubs and trees. Whilst such measures can be effective, if correctly applied, the process can disturb or destroy indigenous plants alongside the weeds and also the remaining seed load may require followup for many years.

Stink Bean - Acacia Lopantha.  Noxious weed. Often confused with Black Wattle (Acacia Mearnsii) . This tree seeds prolifically and forms impenetrable thickets (like Port Jackson). Its seeds remain viable for many years and huge seed loads can accumulate. It is a particular threat to rivers where it invades the banks and can cause blockages and subsequent wash aways of abutting land. 

This picture was taken on the slopes of Chapmans Peak - the Bearded Protea in the foreground will soon be engulfed in Stinkbean without intervention.

A common urban noxious weed.
lantana Camara - Noxious Weed - One of the world's "top ten" weeds.   Widespread in Hout Bay  and very difficult to control.

Primary Alien Vegetation Control (PAVCO) is the control of newly identified infestations of weeds and invasive aliens shortly after emergence where it is relatively easy to remove seedlings and as the seed load is low, it is unlikely that re infestation will be significant. The methodology of control of the two types of infestations is very different, however, the ultimate aim is the same - the control of alien weeds.

Legal definitions of weeds.
For the purposes of the following discussion, classified weeds are described as "noxious" or "invasive". These definitions are described in the "Conservation of Agricultural Resources Act (No 43 of 1984) and embedded in schedules addressed by the accompanying regulations. Noxious weeds are usually toxic to man or cattle in some way and may infest crops  rendering entire harvests unusable in some cases. The penalties are very harsh for harboring weeds of this type and the law is equally applicable on urban as well as rural land, however, in practice the law is rarely if ever invoked in urban areas.

Though still classified as weeds - some are defined as "invasive" and not "noxious". By law, the owner of the land on which invasive weeds exists is liable for prosecution only if the weeds on his or her land are affecting others. eg. An owner having invasive weeds is only obliged to remove them if they represent a threat to other landowners who express their objection to the risks attached to their presence or who are  directly affected by them.

A good example is Morning Glory (opposite) which is a declared invader and can be very difficult to eradicate. Hout Bay has a high incidence of this weed.

Morning Glory (Ipomoeo purpurea) is widespread in gardens in Hout Bay and is difficult to eradicate.

Hout Bay Jan 2000

VELD FIRES are a vital part of the natural fynbos cycle and are an important component for the survival and regeneration of the species.

Alien vegetation, which  burns for too long and at too high a temperature, can irrevocably destroy fynbos as well as endanger lives.

There are of course many  invasive weeds which are not legally classified as such and currently they can only be legally controlled by the enforcement of local Bye-Laws where they have been promulgated. Examples of this could be Pampas Grass which is fast becoming troublesome in Hout Bay and needs outlawing in such a manner as it has been done in Knysna by a local bye-law. However, DWAFF (Dept of Water Affairs & Forestry) have recently taken the initiative to have the regulations revised to correct this anomaly.

Aliens not only destroy our fynbos by overcrowding, they are also great threats to our ground water reserves and present great fire risks - particularly when established on our Urban Edge.  The National Veld & Forest Fire Act has not been applied in this respect and urgently needs implementation in the Peninsula.

Many alien control programs have been undertaken in the Peninsula over the years but invariably funding is the factor which has prevented sustained success. The greatest fire risks occur along our "Urban Edge" where alien vegetation often "escapes" from private gardens and where fire breaks are not maintained.

The question therefore is :-

What is the sustainable solution?  How do we identify and control infestations at an early stage, when costs are minimal but where outbreaks could occur almost anywhere  -   in the Park - along the Urban Edge - on Municipal Land and within Communities on Private Land?

The only way is a holistic approach. Our exacerbated fire problems are caused by Alien Vegetation, our loss of ground water is caused by Alien Vegetation, the threat to our floral biodiversity is caused by Alien Vegetation. All these threats are attacks on our Natural Environment which is the greatest hope we have for the expansion of tourism which the experts tell us will lead to our economic salvation.

In their book "Environments into the 21st Century" Clem Sunter, Prof Roy Siegfried and Brian Huntley point out that ours is the first generation capable of destroying the earth but at the same time they similarly point out that we are the first generation that has the capacity to do anything about the earth's environmental destruction. The answer they argue is TECHNOLOGY,  and PAVCO has been conceived to harness that power.

PAVCO's methodology addresses the alien problem in a new way which draws together the Park, MLC's and Communities, the whole system being based on  the powerful tools that technology today can offer us.

Why is PAVCO different?
Primary Alien Vegetation Control means controlling alien infestations in a defined area as rapidly as possible after detection within that area. It means that as soon as an infantile infestation is identified a predetermined action plan is called for to control it which in turn means that for it to be successful the detection mechanism in the area under control must be free of loopholes or unmonitored "cells". If one takes the Cape Peninsula including the New Cape Peninsula National Park as an example, monitoring must not only take place in the Park but also comprehensively in the abutting communities and municipally owned areas.

How can information be collected?
We believe that in the south peninsula, valuable information can be collected by suitably identified and screened community volunteers having demarcated areas under their control. (Typically a 1Km square). Each volunteer will have a detailed map of his  or her area showing Erven boundaries and key points for orientation purposes. The identification and assessment of the severity of the infestation would be done by that person (with training) and the details including the location reference are recorded in a GIS computerised model (Geographic Information System).  The data being collected via the Internet.

How is the information system used?
Once the data is collected into a central database, a prioritised action plan is  generated for passing on to the group who will take the actual physical control measures in the areas concerned. This is done via what is called a "Problem Management System" (PMS) which monitors problems according to their importance and allocates them to resources for action and subsequent follow up. The PMS also accesses deeds records and can generate letters warning landowners who have problems on their property.

How is physical control applied?
The range of measures needed will depend on the extent and risks attached to each specific incidence. Infantile infestations in certain areas could be controlled by the person who discovers the incidence. On the other hand established infestations may need extensive resource, they could also overlap into the SAVCO arena. The emphasis of PAVCO is on early detection and control, where minimal resources are needed, based on the ability to accurately locate the infestation and get to it to apply mechanical or possibly chemical control on a relatively small scale.

How is followup achieved ?
The Problem Management System (PMS) will not only help to prioritise action it will also help to create a follow-up plan needed to ensure that annual/seasonal checks are undertaken as seeds may remain dormant for many years.

What other information can be gathered?
The Geographic Information System can be used for many other forms of reporting which could include things like the positions and maintenance status of fire breaks, illegal dumping and filling, illegal signage, incidence of endangered species, significant trees which may be under threat, sources of river pollution and any number of other things that need to be monitored right down to man-hole covers!

What are the legal aspects?
Currently the laws regarding alien control are applied by the Department of Agriculture and are not really tailored to urban and peri-urban environments. Local bye-laws need to be created to give additional clout to local authorities to help communities take action. (Feb 2000. DWAFF are known to have vigorously investigated alien legislation and are on the point of making comprehensive recommendations which will be an enormous step forward.)

If you want to Know more about PAVCO contact houtbay@zsd.co.za

D.C. rev 2/2000