Invasive weed control at the Colbyn Valley Wetland

Community members gathered in numbers for a ‘pompom hack’ and to participate in the release of biocontrol agents for pompom weed in the Colbyn Valley Wetland in Pretoria on 15 February 2014.

This activity formed part of World Wetlands Day 2014 celebrations. The event was led by the Agricultural Research Council (ARC), in partnership with the Water Research Commission (WRC), Centre for Wetland Research and Training (WETREST), Friends of Colbyn Valley, South African Wetland Society and City of Tshwane.

This year’s theme for World Wetlands Day is ‘Wetlands and Agriculture: Partners for Growth,’ placing a focus on the need for the wetland, water and agricultural sectors to work together to achieve the best shared outcomes.


Pompom weed is rapidly becoming the most serious threat to the conservation of grasslands in South Africa. Infestations become conspicuous when the plants are in flower between December and March, transforming the veld from green to pink. The plant initially establishes itself in disturbed sites such as roadsides, and invades natural grasslands, open savanna and even temporary and seasonal wetland areas. This weed displaces native species, reducing both the biological diversity and carrying capacity of rangelands.


 Participants in the ‘pompom hack’ and biocontrol release comprised mostly of youth from organisations such as the Voortrekkers and Scouts as well as learners from schools in the area who were accompanied by their parents. Members of the general public who had read about the event in the press also attended. The day began with a short introduction to the Colbyn Valley Wetland by Philip Calinikos of the Friends of Colbyn Valley. WETREST’s Piet-Louis Grundling, a renowned wetland and peatland expert, explained the role and importance of wetlands, followed by an overview of pompom weed and its control by Hildegard Klein from ARC PPRI. In an interesting and entertaining way, Mr Grundling also shared his knowledge about wetlands in the field, pointing out the characteristic features of wetland soils and plants.


Participants had the opportunity to tie twigs bearing hundreds of pompom weed thrips (the biocontrol agent recently cleared for release on pompom) to stems in the most pompom-infested areas of the wetland. They also uprooted 118 pompom weed plants in approximately 20 minutes. This may seem small but, taking into account that each pompom plant can give rise to 1 000 in the next season, it is noteworthy!  Later in the day the learners worked in groups to demonstrate their newly-gained knowledge and built models of the wetland in a light-hearted but competitive way. The enthusiastic response of the public to this event clearly demonstrated the need for such information-sharing sessions, particularly on topics such as alien plant control and wetland conservation.


The Colbyn Valley Wetland includes areas of peatland (the peat layer is estimated to be about 7000 years old) and is in the process of being declared as a nature reserve.  The wetland is vulnerable to a number of impacts due to its urban location, but remains a valuable biodiversity and water resource, as well as offering the residents of Pretoria a unique educational and recreational resource. The Colbyn Valley Wetland has recently received much attention in the press due to concerns over greater stormwater flow from increased development in Hatfield and the proposed park-and-ride facility mentioned in the Hatfield Spatial Development Framework.


The WRC’s involvement in wetland conservation and education initiatives such as the above reflects the value of these ecosystems in providing essential natural infrastructure for managing the country’s water resources. South Africa is the third richest country in the world in terms of biodiversity and has over 120 000 wetlands, covering about 7% of the country’s land area. A total of 20 sites are designated as Wetlands of International Importance (Ramsar Sites), with a surface area of 553 178 hectares. Wetlands provide significant economic, social and cultural benefits. They are important for primary products such as pastures and support recreational and tourist activities and are also important sites for biodiversity. They help reduce the impacts of storm damage and flooding, maintain good water quality in rivers, recharge groundwater and store carbon. 



In addition to providing essential information to support the conservation and management of South Africa’s wetlands, WRC-supported wetland research has made a valuable social and institutional contribution. An estimated 74% (R37 million) of the WRC’s investment in wetland research was used to procure the services of nearly 70 research organizations and nearly 180 researchers. Approximately 70% of the projects supported career development and employment, through education and training of post-graduate students and emerging researchers.

Leave a Reply

Your email address will not be published.