While there have been assurances made by authorities on the successful control of the Salvinia weed in the Okavango Delta water system, latest indications are that the invasive plant remains very much a threat.
Salvinia Weed or Salvinia molesta, an invasive aquatic plant that poses serious harm to the ecosystems’ biodiversity, taking over water watercourses is a nightmare to any wetland if left uncontrolled, as it literally kills other plant species and blocks channels, its other name, Kariba weed is derived from the fact that it infested a large part of Kariba some years back.
Infestations have been identified much lower in the Okavango Delta downstream, which spells a much more serious threat if these mats had come downstream with flood water, boats or animal movements from upstream. This would pose serious consequencies on the tributaries and water courses.
Recently, the North West District Council sent team of councillors and government officials to investigate the cause of low water down flows from upstream through some tributaries and the findings were shocking: with papyrus and salvinia weed cited as the major contributors to these blockages.
As low and downstream as the Santantadibe River, by the buffalo fence near Daunara Village, The Ngami Times team recently came across a large infestation of the weed, atleast a kilometre of what the team was able to visualise. This (as the image above shows) is a complete cover, with mats have taken over this very important part of the River. On this particular trip, officials from the Water and Sanitation department were on site taking samples of the weed.
What was even concerning about the particular site of infestation is that it is frequented by members of the community, tour operators, government officials and tourists alike as it’s under a wooden bridge that connects settlements in the area – yet it still spread to the extent it did unabated.
However, as fate would have it – an event to hand over a newly constructed bridge at the site presented an opportunity for the Water and Sanitation officials in attendance to speak to the other stakeholders about the infestation of salvinia.
Speaking at this event, Itseng Kgosidialwa water engineer with the department pointed to the failure to report infestations to their offices in time and during dry seasons when the weed can easily be removed as the major challenge. The official would go on to urge members of the public to report the infestation, for early physical control and avoid the catastrophic effects of the weed.
Contrary to assertions by the department – some villagers who spoke to this publication would point to the department for its failure to act on their reports, adding that by the time such responses are made the infestations would have covered proportional levels. They also revealed that in most instances the mats of the weed come down with the flood waters from upstream, then edging on lagoons along the water ways.
To further illustrate their extensive understating of the dangers posed by Mutjimbamo – as they refer to the weed, they revealed that the weed can single headedly block a channel, ensure that all living organisms living under water suffocates due to lack of oxygen and sunshine, with other plant species dying in the process.
This would prevent access to the channel, and their livelihoods affected at they cannot fish, or get reeds from the river. The covered watercourses also become a threat to their lives as it becomes easy for one drown in the covered lagoons and channels.
Government has over the years led in the control of the Salvinia Weed, opting for the most effective biological method – of using salvinia weevils, that bred and released onto a site whenever there is an infestation. The weevils wood feed on the flooding weed, until its destroyed. In the previous years, various environmental projects spanning the wetland and 1000th World Heritage Site, funded by donor agencies also had a part on controlling the weed, and trained safari workers in camps on salvinia control, and the breeding of weevils. Safari workers in the delta were capacitated on dealing with the weed first hand without consulting authorities.
