Conservation

CONSERVATION CONCERNS AT VERMONT AND ONRUS WATER BODIES

Posted on the 11th January 2021

We organised a site visit with Dr Giselle Murison, the Western Cape Estuaries Conservation Project Manager of BirdLife South Africa on Thursday 17 December 2020. This was in reaction to several concerns that we had expressed about the conservation status of both the Vermont salt pan and the Onrus River estuary. The results of previous Coordinated Water Bird Counts (CWACs) at these two sites clearly suggest changing and fluctuating bird numbers, an issue that needs further investigation.

There had been a few incidents of die-offs of water birds at the Vermont salt pan in the past suggesting the possibility of poisoning. In the past there had been some incidents of sewage spills as well as chemicals leaching into the pan after exotic trees had been cut down. The possibility of avian botulism outbreaks can however not be discounted. Dr Murison did commit to ensure that regular water quality testing be undertaken in future in view of developing a better understanding of potential problems facing birds at the pan.

There had also been a dramatic increase in volume of a particular grass-type around the edges of the pan. This has essentially taken away most foraging space for waders at the pan. A gulley that had in the past produced sightings of a variety of ducks and rallids had in fact been totally overgrown by this grass with no water being visible. The feeling was that the sudden increase of this grass probably indicates some changes in the water quality and this is seen as a further motivation for regular water quality testing at the pan. Dr Murison did however take some photographs of the grass (and its extensive root system) in view of further investigation.

The long-standing problems with sewage spills from a pump station at the Onrus River estuary and the resulting very high ecoli counts are well documented and regularly receive negative publicity in both the printed and social media. Concerned citizens are placing continual pressure on the Overstrand local municipality and the local councillor Jean Orban to rectify the situation. There had been a massive increase of reeds along the banks of the estuary to the extent that there is literally no foraging space for waders any longer. The entire profile of bird species had changed dramatically as a result of this as indicated by the huge reduction of birds counted during recent CWACs.

The possible removal and/or management of the reeds at the Onrus River estuary are currently being considered. We have drafted a report on this for the project consultants in which the problems facing birds at the estuary are described in relative detail. This report can be studied as background information:

http://www.westerncapebirding.co.za/overberg/conservation/700/the_management_of_invasive_reeds_at_the_onrus_river_estuary

Dr Murison further expressed concern about the height of the reeds during our site visit to the estuary. This is clearly an indication of the increase in nutrient levels at the estuary which could be explained by the regular sewage spillages into the estuary.

The site visits clearly indicated that ongoing monitoring at these two important water bodies would be of critical importance. This applies to regular CWAC counts as well as water quality testing. It is hoped that Dr Murison’s involvement will contribute to the development of meaningful mitigating measures to ensure the sustainable conservation of these two important water bodies. The Vermont salt pan and the Onrus River estuary need to be protected particularly as far as birding tourism is concerned.

Anton Odendal
January 2021.


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