Alien grasses: The current local perspective and forming a “National Working Group on Alien Grasses”

Alien grasses: The current local perspective and forming a “National Working Group on Alien Grasses”
Vernon Visser1 and John Wilson1,2
1Centre of Excellence for Invasion Biology, Private Bag X1, University of Stellenbosch, Matieland 7602,
2Invasive Species Programme, South African National Biodiversity Institute, Private Bag X7, Claremont, 7735..
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The grasses form the fourth largest plant family with over 11,000 species with some of the most important crop and pasture species, so it is not surprising that many grass species have been extensively moved around the world. Some of the best examples of invasive species causing radical ecosystem transformations are also the result of introduced grasses—e.g. radically altered fire regimes—with grasses of African origin having often the largest impacts. Comparatively, Africa appears to have suffered far smaller impacts from invasive grasses, with some notable exceptions, e.g. giant reed (Arundo donax), Pampas grass (Cortaderia selloana) Kikuyu grass (Pennisetum clandestinum) and a number of annual grasses of Eurasian origin. Grasses have also received far less attention than woody plants in South Africa, not least because of the difficulty of distinguishing between many grass species. This suggests that there are probably far more exotic grass species in South Africa, at various stages of the invasion process, than we are currently aware of. In addition, increased interest in growing exotic grass species for biofuel (e.g. Arundo donax, Miscanthus spp., Sorghum halepense) or for carbon offsetting (e.g. various bamboo species; e.g. www.trees.co.za/bamboo-for-africa/) is resulting in the introduction of new species and genetic strains of species, and extensive plantings of these species, making the chances of these species becoming invasive much more likely.

Revisiting the paper by Milton in 2004, I will discuss the current state of knowledge of alien grasses in South Africa and around the globe, and provide a brief overview of current and potential impacts of alien grasses both locally and globally. I will then provide an overview of a proposed alien grass working group for South Africa, whose aims will possibly be twofold:

1)   producing an inventory of all known alien grass species in South Africa;

2)   and conducting a national risk assessment of potential alien grass invaders.

Anyone interested in participating in a working group to achieve these aims is encouraged to attend. This session is intended as an open platform for discussion on the issue of alien grasses in South Africa and the input from interested parties would be most welcome. We also intend to set dates for a possible workshop to be held in Stellenbosch, to further the abovementioned aims.

REFERENCES

CLAYTON, W.D., HARMAN, K.T. & WILLIAMSON, H. 2006 onwards. GrassBase - The Online World

Grass Flora. Available at http://www.kew.org/data/grasses-db.html.

D'ANTONIO, C. & VITOUSEK, P.M. 1992. Biological invasions by exotic grasses, the grass/fire cycle, and global change. Annual Review of Ecology and Systematics 23: 63-87.

VAN WILGEN, B.W., REYERS, B., LE MAITRE, D.C., RICHARDSON, D.M. & SCHONEGEVEL, L. 2008. A biome-scale assessment of the impact of invasive alien plants on ecosystem services in South Africa. Journal of Environmental Management 89: 336-349.

MUSIL, C.F., MILTON, S.J. & DAVIS, G.W. 2005. The threat of alien invasive grasses to lowland Cape floral diversity: an empirical appraisal of the effectiveness of practical control strategies. South African Journal of Science 101: 337-344.

MILTON, S.J. 2004. Grasses as invasive alien plants in South Africa. South African Journal of Science

100: 69-75.

HENDERSON, L. 2007. Invasive, naturalized and casual alien plants in southern Africa: a summary based on the Southern African Plant Invaders Atlas (SAPIA). Bothalia 37: 215-248.

BLANCHARD, R., RICHARDSON, D.M., O’FARRELL, P.J. & VON MALTITZ, G.P. 2011. Biofuels and biodiversity in South Africa. South African Journal of Science 107: 19-26.