We might underestimate impacts of alien grasses in South Africa due to limited data availability

Alien grasses occurring in South Africa have been associated with negative environmental and socio-economic impact across the globe. Some grasses can increase the intensity and frequency of fires due to their large biomass, and many grass species invade areas such as agricultural land leading to reduced crop yield and quality.

Dallas grass (Paspalum dilatatum) invading cultivated hey grass at the Cedara Research Centre, KZN

Dallas grass (Paspalum dilatatum) invading cultivated hey grass at the Cedara Research Centre, KwaZulu-Natal. (Photo credit: Khensani Nkuna)

In a paper published in Neobiota, former Masters student Khensani Nkuna and her supervisors Sabrina Kumschick (C·I·B Core Team Member), John Wilson (C·I·B Core Team Member) and Vernon Visser (former C·I·B post-doc) used the Generic Impact Scoring System (GISS) to assess the impacts of grasses alien to South Africa. Khensani collated global literature on the environmental and socio-economic harm caused by these grasses in South Africa and in other introduced countries in order to estimate their potential negative impacts in South Africa and to use those estimates to rank the grasses to feed into management prioritisation.

The authors found that the grasses cause diverse negative impacts across most habitats and regions where they occur. Their ranking indicates that Pampas grass (Cortaderia selloana) has the highest overall impacts due to its multiple ways of causing impacts. They also found that competition with native and agricultural plants is the most frequent way in which most alien grasses cause negative impacts.

“Using impact records from different introduced ranges can be useful in predicting the potential negative impacts of a target species in an area where the species has not yet been studied, which is the case for most alien grasses in South Africa” says the lead author Khensani Nkuna. “Such potential negative impacts can also be important in motivating for the allocation of management resources of a species which has not yet shown such impacts in an area.”

Read the paper in Neobiota

Nkuna KV, Visser V, Wilson JRU, Kumschick S (2018) Global environmental and socio-economic impacts of selected alien grasses as a basis for ranking threats to South Africa. NeoBiota. 41: 19�65.

For more information, contact Sabrina Kumschick at