“Invasive alien species represent the second most significant cause of species extinction worldwide after habitat destruction. The impacts of alien invasive species are immense, insidious, and usually irreversible,” states the International Union for Conservation of Nature (IUCN).
Their concerns are supported by organisations such as Birdlife South Africa, Environmental Programmes, CapeNature, the South African National Biodiversity Institute’s (SANBI) Invasive Species Programme, Animal Demography Unit (University of Cape Town), Centre for Invasion Biology (Stellenbosch University), Cape of Good Hope SPCA, Western Cape Invasive Alien Animal Forum, KwaZulu-Natal Invasive Species Forum and the National Invasive Species Forum.
The National Invasive Species Forum is funded by Environmental Programmes (EP), Department of Environmental Affairs, which is mandated to manage South Africa’s natural resources through public employment programmes for poor and marginalised communities. EP addresses the threats posed by invasive species through programmes such as Working for Water, Working for Wetlands, Working on Fire and Working for the Coast. They also fund partners, such as the City of Cape Town to implement projects that remove invasive flora and fauna (including Mallard Ducks) within the city. To download a mallard identification kit, click here.
Acknowledging mounting scientific evidence, the National Government has recently passed legislation to protect indigenous species from extinction due to invasions by alien fauna.
Regulations relating to the National Environmental Management Biodiversity Act 10, 2004 (NEMBA) were published in the Government Gazette on 19 July, 2013. In these regulations, the Mallard Duck (Anas platyrhynchos) is listed as a category 1b species, which means it is now an invasive species of national concern which requires control, as part of a management plan, by all conservation authorities across the country.
The Invasive Species Unit of the City’s Environmental Resource Management Department is at the forefront of international best practice when it comes to protecting the City’s indigenous species from alien invasions.
In 2011, the unit was selected to implement the Kader Asmal Integrated Catchment Management Project (Kader Asmal ICMP) which formed part of Mayor De Lille’s Special Job Creation programme to create work opportunities for disadvantaged Capetonians and assist in the clean-up of 20 water catchments.
Operating as an interdepartmental, cross-cutting project, the Kader Asmal ICMP assisted in the clearing of invasive water hyacinth from the Black River, which resulted in the celebrated return of pink flamingoes.
Saving our indigenous waterfowl
Whilst the removal of invasive alien plants has been in progress of over a decade, the City is now compelled through national legislation to protect endemic and indigenous fauna from invasions by exotic or alien fauna.
Working closely with avian experts from Birdlife South Africa, SANBI Invasive Species Programme and UCT’s Animal Demography Unit, waterfowl such as the Yellow Billed-Duck, African Duck and Cape Teal were identified for a publicity campaign. In 2012, the ‘Save our Indigenous Waterfowl’ campaign was launched in the City.
Lauded as a first in the country, the campaign has since been adopted by a number of conservation bodies in KwaZulu-Natal, who are also eager to protect their own endemic and indigenous waterfowl from invasive ducks.
Full-colour Mallard Duck identification kit invasive alert pamphlets, which aim to educate City residents on how to identify Mallard Ducks in local water bodies, were also released.
The invasive alien Mallard Duck (Anas platyrhynchos) is a very attractive duck which historically comes from the Northern Hemisphere and was introduced locally to ponds and wetlands, primarily through the pet trade.
Scientists have now shown conclusively that Mallards threaten the survival of closely-related indigenous ducks in many parts of the world. In South Africa, Mallards crossbreed with various indigenous ducks such as the Yellow-Billed duck (Anas undulata), the African Black duck (Anas sparsa) and Cape Teal (Anas capensis).
The off-spring of Yellow-Billed Ducks and Mallard Ducks are fertile. Scientists are concerned that this crossbreeding may result in the extinction of the indigenous Yellow-Billed Duck.
Examples elsewhere in the world serve as a serious warning to South Africa. The American Black Duck numbers have drastically declined and the Mexican duck is now extinct because of hybridization with Mallard Ducks.
In Hawaii, the Hawaiian Duck is under threat from hybridisation and the New Zealand Grey Duck, once considered the most widespread and abundant duck in New Zealand, is highly threatened and now only makes up 5% of the total Mallard-hybrid-Grey Duck population.
Scientists warn that if steps are not taken locally, the Yellow-Billed Duck will soon face the same fate as these ducks.
As invasive aliens, Mallards easily out-compete indigenous ducks for resources such as food and space in the habitats where they occur. Male Mallards are also aggressive breeders, often targeting individual indigenous female ducks in groups.
As part of a national strategy, and in accordance with national environmental laws, the City of Cape Town is responsible for managing Mallard Ducks in the metropole.
In preparation for this task, the City will continue to promote the ‘Save our Indigenous Waterfowl’ education campaign and make invasive Mallard Duck identification posters available by request or downloadable online.