Chapter 2. Trends and status of alien and invasive alien species

Chapter 2: Trends and status of alien and invasive alien species of the Thematic Assessment Report on Invasive Alien Species and their Control of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services

Evidence for induced pseudo-vivipary in Pennisetum setaceum (Fountain grass) invading a dry river, arid Karoo, South Africa

We report the development of rootless plantlets in inflorescences of Pennisetum setaceum (Fountain grass) invasive in the Gamka River in the Karoo National Park, South Africa. The pseudo-vivipary appeared to have been induced by inundation of immature inflorescences when the river flooded. Plantlet production may facilitate the spread of this species in seasonally flooding rivers in arid regions. To the best of our knowledge this is the first record of induced pseudo-vivipary in this grass species. © 2007.Articl

Performance of invasive alien fountain grass (Pennisetum setaceum) along a climatic gradient through three South African biomes

The knowledge of relative performance of plants across environmental gradients is critical for their effective management and for understanding future range expansion. Pennisetum setaceum is an invasive perennial grass found along roadsides and other disturbed sites in South Africa. The performance of this grass in response to competition, habitat characteristics and resources was experimentally tested in three biomes (Karoo, Fynbos and Savanna) of South Africa. A total of 846 young P. setaceum seedlings were translocated to study sites in May 2007. The seedlings were grown in 94 plots along randomtransects, of which alternate halves were cleared of vegetation. Despite a variety of environmental hazards at these sites, over 30% of the transplanted seedlings survived over 15 months. Competition from resident vegetation was a major factor limiting the establishment of seedlings. However, under adequate rainfall and historical disturbance (mine dump), competition effects were overridden. Survival of seedlings was greatest in the Karoo National Park, possibly because of summer rainfall that occurred shortly after translocation. Despite differences in the survival and growth rates, seedlings remained alive at all sites, especially if they survived the first sixmonths after translocation. P. setaceumis capable of persisting across a broad range of environmental conditions. Management efforts should aim to reduce seed production and establishment along roadsides that act as conduits into protected sites. This could be best achieved by maintaining as much indigenous cover along road verges as possible, as seeds survive best where competition is low

Indicators for monitoring biological invasions at a national level

1. A major challenge for the management of biological invasions is to ensure that data and information from basic inventories and ecological research are used alongside data from the monitoring and evaluation of interventions to trigger and improve policy and management responses. To address this issue, South Africa has committed to report on the status of biological invasions and their management every 3 years. 2. We propose a framework of indicators for reporting on biological invasions at a country level; assess the feasibility of the indicators using South Africa as a case study; and outline steps needed for indicator development. 3. We argue that a national status report on biological invasions should explicitly consider indicators for pathways, species, and sites, and should report on interventions in terms of inputs, outputs, and outcomes. 4. We propose 20 indicators based on data currently available, as well as existing international policy initiatives. For each indicator, we have developed a factsheet that includes different hierarchical metrics (considering data availability) and provide suggestions on assigning confidence levels. We also combine these indicators into four high-level indicators to facilitate broader reporting and describe how forecasted indicators based on the concept of invasion debt could assist with scenario planning. 5. We found that many of the data required for these indicators are already available in South Africa, but they have been poorly collated to date. However, data for the indicators of most direct value to policy and planning—those dealing with the impact of biological invasions and the outcome of interventions—are scarce. 6. Policy implications. The framework of indicators developed here, for what we believe is the first ever national-level report on the status of biological invasions and their management, will facilitate the inclusion of biological invasions in environmental reporting at national and international levels. By identifying knowledge gaps, a status report will also focus efforts on determining the size of a country’s invasion debt and what can be done to reduce it