An approach to the development of a national strategy for controlling invasive alien plant species: The case of <i>Parthenium hysterophorus </i> in South Africa

Abstract

Invasive alien species require co-ordinated strategic management if negative impacts are to be effectively avoided. Here we describe a strategy for the management of Parthenium hysterophorus L. (Asteraceae) in South Africa. P. hysterophorus is an annual herb native to tropical America, which has become invasive in over 30 countries. The strategy sets goals for (1) the prevention of spread to new areas; (2) local eradication of isolated populations; (3) containment in areas where eradication is not possible; and (4) actions to protect assets where containment is no longer an option. We developed both a national strategy to set policy and to monitor progress towards goals at a national level and an implementation plan to set goals and timeframes for their achievement at local levels. It is not clear, at this stage, whether or not the goals of the strategy are achievable because implementation will face many challenges arising from ecological features of the target plant, social and cultural practices that will influence management, inadequate levels of funding and multiple political considerations. Our strategy proposes regular assessment using high-level indicators, a practice that is widely recognised as essential but seldom implemented at a national scale. Because the outcomes are uncertain, it is vital that regular monitoring of outcomes should be instituted from the start, so that both appropriate adjustments can be made to the strategy and lessons for the implementation of similar strategies elsewhere can be derived.

Niche change analysis as a tool to inform management of two invasive species in Eastern Africa

“…Both P. juliflora and L. camara have become widely established in Eastern Africa, necessitating a spatially explicit management strategy that ensures concerted communication and management across national and subnational borders and sets different control objectives for areas with different invasion levels (Grice et al 2011, Terblanche et al 2016, Shackleton et al 2017b). By combining different approaches to assess the two species' ecological niches and stages of invasion and the probability of their potential distribution in space and time, our study generated a number of results with direct implications for management ( Table 4).…”

“…Once an IAPS has established itself widely in its introduced range, complete eradication is no longer feasible (Parkes and Panetta 2009). Rather, it should be managed according to a spatially explicit management strategy that sets different control objectives for areas with different invasion levels (Grice et al 2011, Terblanche et al 2016, Shackleton et al 2017b). Developing such a strategy requires a holistic understanding of a species' stage of invasion and the invasion process, including factors affecting its local abundance, spread, and impact.…”

Feature Selection on Sentinel-2 Multispectral Imagery for Mapping a Landscape Infested by Parthenium Weed

“…On invaded landscapes, Parthenium weed expands more rapidly than native plants [60]. Spectral bands alone are not enough to achieve reliable mapping accuracies [61].…”

An assessment of the evolution, costs and effectiveness of alien plant control operations in Kruger National Park, South Africa

“…At the same time, however, the flood disturbance probably facilitated the invasion of other species such as C. odorata Martin 2002, Leroy 2003). No data existed for the effectiveness of P. hysterophorus control either, but this species is spreading rapidly and is recognised as a substantial problem in KNP, as elsewhere (Terblanche et al 2016). Anecdotal (and photographic) evidence can also be cited in support of progress made with the control of aquatic weeds (Fig.…”

“…Although there is a dedicated set of protocols for the management of this species in KNP, there has until recently been no monitoring of the effectiveness of management (although this is currently being initiated). As is the case elsewhere in South Africa, the long-term control of this species will probably have to rely heavily on the current efforts to curb further spread and the development of biological control options that will make mechanical and chemical clearing viable (Terblanche et al 2016).…”