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South African National Alien Grass Working Group

South African National Alien Grass Working Group

Who are we?

Jointly initiated by the South African National Biodiversity Institute (http://www.sanbi.org/) and the Centre for Excellence in Invasion Biology (C·I·B) in August 2013 by a group of researchers and managers concerned about the impacts of alien grasses in the country.

Our aims are to:

    • Strategically monitor and coordinate information on invasive alien grasses in South Africa
    • Provide a collaborative approach to alien grass research and management
    • Raise awareness of new alien species and new incursions
    • Produce a list of priority invasive alien grasses and priority areas for management
    • Assess the risks posed by alien grasses and the feasibility of management
    • Develop best practice control methods of target grass species
    • Facilitate better communication between research institutes, invasive species managers and relevant government departments
    • Provide information for queries on grass introductions/permits
    • Provide policy recommendations

Why? ( focus species / area )

The grass family (Poaceae) is the fourth largest plant family with over 11,000 species and with some of the most important crop and pasture species. It is therefore not surprising that many grass species have been extensively moved around the world. Some alien grass species have caused major ecosystem transformation—e.g. radically altered fire regimes—with grasses of African origin often having the largest impacts.

Comparatively, Africa appears to have suffered far fewer and less severe impacts from invasive grasses, with some notable exceptions, e.g. giant reed (Arundo donax), Kikuyu grass (Pennisetum clandestinum) and a number of annual grasses of Eurasian origin.

In South Africa, grasses seemingly have had little impact on ecosystems, but this lack of an observed impact may be largely due to the fact that this group of plants has received so little attention from invasion researchers and managers.

There is very good reason to be concerned because South Africa is comparable to countries like Australia and the USA in terms of numbers of grass species introduced, and has at least 122 species that are surviving and reproducing in the wild, but that have yet to become serious invaders.

Our research

  1. Grasses as invasive plants in South Africa revisited

One of the main outputs of this Working Group has been to compile a comprehensive review of alien grasses in South Africa (Visser et al. 2017). This revealed that there are at least 256 alien grass species in South Africa, of which 122 have naturalised and 37 have become invasive (this represents an 8% increase in the number of naturalised species since 2004).

Alarmingly, more recently many grass species appear to have been introduced accidentally, suggesting the possibility for new invasions. Our review highlighted the need for much greater investment in alien grass management, research and legislation, particularly since we appear to be saddled with a large grass invasion debt, i.e. a large number of species likely to become invasive in the future.

  1. Biocontrol of grasses

A team from the Centre for Biological Control, Rhodes University are currently involved in researching the prospects for classical biological control of alien grasses. To date, only two grasses, Arundo donax and Spartina alterniflora have had releases of biological control agents globally. The team is hoping to expand research on this group and see more invasive grasses targeted for biocontrol. Their research has involved surveys for natural enemies and host-specificity testing for potential biological control agents on invasive alien grasses (Andropogan gayanus, Arundo donax, Eragrostis curvula, Megathyrsus maximus, Sporobolus natalensis, S. pyramidalis)

  1. Bamboos

In 2014, the Alien Grass group identified the need for research on the increasing popularisation of bamboos in South Africa, and the potential for new invasion risks. This work was taken up by Dr. Susan Canavan at Stellenbosch University, jointly funded by the Centre for Invasion  Biology (CIB)  http://academic.sun.ac.za/cib/news/20130820_alien_grasses_group.htm and SANBI. Susan has reviewed the global transfer of bamboos, her work has included producing a complete species list of bamboos (c. 1600 species), mapping the native and introduced and distribution of bamboo, reviewing impacts, as well as exploring correlates (traits, phylogeny, cultivar diversity) of invasion success. She has also looked at the introduction history of bamboos in South Africa, and the perceptions of landowners on its value.

  1. Risk & impact assessments

Khensani Nkuna has done detailed impact analyses for selected grasses recorded as alien in South Africa and elsewhere in the world. Her research has shown that grasses score similarly for impacts, regardless of where they occur as aliens. This highlights the dangers posed by the many alien grasses in South Africa that are, as yet, not widespread but already established in the country. She has also investigated the risk posed by Paspalum quadrifarium, a species with a relatively restricted distribution in South Africa and first recorded in only 2003. Her research clearly shows that areas invaded by this species are undergoing a complete transformation in the plant community, with uninvaded, invaded and cleared areas all having almost completely different groups of plant species. Khensani’s research will provide valuable scientific support for the listing of alien grass species under the NEM:BA regulations.

Current status and regulations of alien grasses in SA

The status, management and control of alien grass species in South Africa is regulated by the National Environmental Management: Biodiversity Act (Act No. 10 of 2004) Alien and Invasive Species Regulations (of 2020). At present 21 species (8 listed only for the Prince Edward and Marion Islands) are listed under these regulations, with varying requirements for controls on their importation, possession, sale, cultivation and management. A further 38 species are prohibited from being introduced into South Africa.

Student bursaries

Meetings

The group meets annually.

Get in contact: 

Chair: Chair: Caroline Mashau, SANBI Email: c.mashau@sanbi.org.za

Secretary: Dr. Kim Canavan, Centre for Biological Control, Rhodes University Email: K.Canavan@ru.ac.za

© Copyright 2021 Invasives SA

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