Original Research

Grasses as invasive plants in South Africa revisited: Patterns, pathways and management

Vernon Visser, John R.U. Wilson, Kim Canavan, Susan Canavan, Lyn Fish, David Le Maitre, Ingrid Nänni, Caroline Mashau, Tim O’Connor, Philip Ivey, Sabrina Kumschick, David M. Richardson
Bothalia | Vol 47, No 2 | a2169 | DOI: https://doi.org/10.4102/abc.v47i2.2169 | © 2017 Vernon Visser, John R.U. Wilson, Kim Canavan, Susan Canavan, Lyn Fish, David Le Maitre, Ingrid Nänni, Caroline Mashau, Tim O’Connor, Philip Ivey, Sabrina Kumschick, David M. Richardson | This work is licensed under CC Attribution 4.0
Submitted: 05 September 2016 | Published: 31 March 2017

About the author(s)

Vernon Visser, SEEC – Statistics in Ecology, the Environment and Conservation, Department of Statistical Sciences, University of Cape Town; African Climate and Development Initiative, University of Cape Town; Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University; Invasive Species Programme, South African National Biodiversity Institute, Kirstenbosch Research Centre, South Africa
John R.U. Wilson, Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University; Invasive Species Programme, South African National Biodiversity Institute, Kirstenbosch Research Centre, South Africa
Kim Canavan, Department of Zoology and Entomology, Rhodes University, South Africa
Susan Canavan, Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, South Africa
Lyn Fish, National Herbarium, South African National Biodiversity Institute (SANBI), South Africa
David Le Maitre, Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University; Natural Resources and the Environment, Stellenbosch, South Africa
Ingrid Nänni, Invasive Species Programme, South African National Biodiversity Institute, Kirstenbosch Research Centre, South Africa
Caroline Mashau, Invasive Species Programme, South African National Biodiversity Institute, Kirstenbosch Research Centre, South Africa
Tim O’Connor, South African Environmental Observation Network (SAEON), Pretoria, South Africa
Philip Ivey, Invasive Species Programme, South African National Biodiversity Institute, Kirstenbosch Research Centre, South Africa
Sabrina Kumschick, Centre for Invasion Biology,Department of Botany and Zoology, Stellenbosch University; Invasive Species Programme, South African National Biodiversity Institute, Kirstenbosch Research Centre, South Africa
David M. Richardson, Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, South Africa


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Abstract

Background: In many countries around the world, the most damaging invasive plant species are grasses. However, the status of grass invasions in South Africa has not been documented recently.
Objectives: To update Sue Milton’s 2004 review of grasses as invasive alien plants in South Africa, provide the first detailed species level inventory of alien grasses in South Africa and assess the invasion dynamics and management of the group.
Method: We compiled the most comprehensive inventory of alien grasses in South Africa to date using recorded occurrences of alien grasses in the country from various literature and database sources. Using historical literature, we reviewed past efforts to introduce alien grasses into South Africa. We sourced information on the origins, uses, distributions and minimum residence times to investigate pathways and patterns of spatial extent. We identified alien grasses in South Africa that are having environmental and economic impacts and determined whether management options have been identified, and legislation created, for these species.
Results: There are at least 256 alien grass species in the country, 37 of which have become invasive. Alien grass species richness increased most dramatically from the late 1800s to about 1940. Alien grass species that are not naturalised or invasive have much shorter residence times than those that have naturalised or become invasive. Most grasses were probably introduced for forage purposes, and a large number of alien grass species were trialled at pasture research stations. A large number of alien grass species in South Africa are of Eurasian origin, although more recent introductions include species from elsewhere in Africa and from Australasia. Alien grasses are most prevalent in the south-west of the country, and the Fynbos Biome has the most alien grasses and the most widespread species. We identified 11 species that have recorded environmental and economic impacts in the country. Few alien grasses have prescribed or researched management techniques. Moreover, current legislation neither adequately covers invasive species nor reflects the impacts and geographical extent of these species.
Conclusion: South Africa has few invasive grass species, but there is much uncertainty regarding the identity, numbers of species, distributions, abundances and impacts of alien grasses. Although introductions of alien grasses have declined in recent decades, South Africa has a potentially large invasion debt. This highlights the need for continued monitoring and much greater investment in alien grass management, research and legislation.

Keywords

Invasive species; Alien; Grass; Poaceae

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1. Impacts of invasive plants on animal diversity in South Africa: A synthesis
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Bothalia  vol: 47  issue: 2  year: 2017  
doi: 10.4102/abc.v47i2.2166