Evaluating the efficacy of invasive plant control in response to ecological factors

Dew, L. Alexander; Rozen‐Rechels, David; Cromsigt, Joris P. G. M.; Beest, Mariska te

doi:10.1016/j.sajb.2016.12.007

Cited by 12 publications

(14 citation statements)

References 36 publications

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“…These results suggest that the focus of clearing programmes should be on the heavily invaded patches (>50% cover) to reduce immediate impacts (Gaertner et al., ), while at the same time managing low‐density areas to prevent them from becoming dense. This approach has been successfully implemented in HiP in the last ten years, albeit at a high economic cost (Te Beest, Howison, et al., ; Dew et al, ). Our results show that these clearing programmes have potential to restore animal habitat selection.…”

Section: Discussionmentioning

confidence: 99%

“…At the height of the invasion, 20% of the northern half of the park (Hluhluwe) was covered in dense C. odorata monocultures, especially along rivers, forests margins and as an understorey in woodlands (Te Beest et al., ). In 2004, Ezemvelo KZN Wildlife (EKZNW—the park's management authority) began a large‐scale clearing programme in collaboration with the provincial government (Te Beest, Howison, et al., ; Dew, Rozen‐Rechels, le Roux, Cromsigt & te Beest ), which reduced densities of C. odorata with success (currently <5% total park cover). Maintenance of the cleared areas is ongoing.…”

Section: Introductionmentioning

confidence: 99%

“…In 2004, Ezemvelo KZN Wildlife (EKZNW-the park's management authority) began a large-scale clearing programme in collaboration with the provincial government (Te Beest, Howison, et al, 2017;Dew, Rozen-Rechels, le Roux, Cromsigt & te Beest 2017), which reduced densities of C. odorata with success (currently <5% total park cover). Maintenance of the cleared areas is ongoing.…”

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confidence: 99%

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Contrasting impacts of an alien invasive shrub on mammalian savanna herbivores revealed on a landscape scale

Rozen‐Rechels

Beest

Dew

et al. 2017

Diversity and Distributions

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Aim Habitat loss and fragmentation is one of the main drivers of defaunation, that is the loss of large mammals. Biological invasions could be drivers of such phenomenon. However, their impact on large herbivore communities has not been studied to our knowledge. We made use of a landscape‐scale control programme of one of the world's worst invaders, the shrub Chromolaena odorata, as a natural experiment to assess how this alien invader affects habitat use by 14 species of ungulates in an African savanna. Location Hluhluwe‐iMfolozi Park, KwaZulu‐Natal, South Africa. Methods At the height of the invasion in 2004, a large‐scale control programme was initiated that successfully reduced densities of C. odorata across the park. We estimated mammalian herbivore habitat and patch use by dung counts and the presence and density of C. odorata along 24 line transects with a total length of 190 km during the peak of the invasion (2004) and a decade after the initiation of a successful control programme (2014). To account for differences in herbivore assemblies between habitats and the preferential invasion of closed savanna woodlands, we analysed the recolonization of previously invaded patches by herbivores based on the change in dung abundance. Results Herbivore species differed in how they responded to invaded patches of this non‐native shrub. Grazers were the most negatively affected, especially those that avoid predators by running. Browsers were negatively impacted only at the highest invasive shrub densities. Some species, especially bushpig, positively selected invaded patches. Main conclusions Large herbivores varied in their response to invasion with differences in impact depending on feeding strategy and predator avoidance strategy, but the majority of ungulates responded positively to the removal of this invasive shrub.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Contrasting impacts of an alien invasive shrub on mammalian savanna herbivores revealed on a landscape scale

Rozen‐Rechels

Beest

Dew

et al. 2017

Diversity and Distributions

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“…The lack of consistent records and monitoring remains a concern, though. As a result there is almost no quantitative evidence that species have been controlled, nor that the measures to control them are appropriate and cost-effective (e.g., Dew et al 2017), and most assessments (for example those supporting statements in the KNP management plan) come from the undocumented observations of park staff. We would, however, caution against complacency.…”

Section: Current Situationmentioning

confidence: 99%

“…biological control, Palmer et al 2010); or had a focus on specific species (e.g. Bonesi and Palazon 2007, Hazelton et al 2014, Lindenmayer et al 2015, Dew et al 2017. For example, Thorp and Lynch (2000) describe how the weeds of national significance were determined for Australia's control program, and Nel et al (2004) describe species prioritization for South Africa's Working for Water program.…”

Section: Introductionmentioning

confidence: 99%

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

Wilgen¹,

Fill²,

Govender³

et al. 2017

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Alien plants were first recorded in 1937 in the 2 million ha Kruger National Park (KNP, a savanna protected area in South Africa), and attempts to control them began in the mid-1950s. The invasive alien plant control program expanded substantially in the late 1990s, but its overall efficacy has not been determined. We present an assessment of invasive alien plant control operations over several decades in KNP. We based our assessment on available information from a range of control programs funded from various sources, including national public works programs, KNP operational funds, and foreign donor funds. Over ZAR 350 million (~ US$ 27 million) has been spent on control interventions between 1997 and 2016. We found evidence of good progress with the control of several species, notably Opuntia stricta, Sesbania punicea, Lantana camara and several aquatic weeds, often because of effective biological control. On the other hand, we found that over one third (40%) of the funding was spent on species that have subsequently been recognised as being of lower priority, most of which were alien annual weeds. The allocation of funds to non-priority species was sometimes driven by the need to meet additional objectives (such as employment creation), or by perceptions about relative impact in the absence of documented evidence. We also found that management goals were limited to inputs (funds disbursed, employment created, and area treated) rather than to ecological outcomes, and progress was consequently not adequately monitored. At a species level, four out of 36 species were considered to be under complete control, and a further five were under substantial control. Attempts to control five annual species were all considered to be ineffective. Brian W. van Wilgen et al. / NeoBiota 35: 35-59 (2017) 36 On the basis of our findings, we recommend that more studies be done to determine impacts associated with individual invasive alien species; that the criteria used to prioritise invasive alien species be documented based on such assessments, so that management can justify a focus on priority species; and that funding be re-directed to those species that clearly pose greater threats, and for which other solutions (such as biological control) are not an option. NeoBiota

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The Extent and Effectiveness of Alien Plant Control Projects in South Africa

Wilgen

Wilson

Wannenburgh³

et al. 2020

Biological Invasions in South Africa

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Since 1995, the South African government has spent at least ZAR 15 billion (unadjusted for inflation; approximately USD1 billion) on alien plant control operations across South Africa. The amount spent per year has risen exponentially since 2010, and in 2019 annual spending is around ZAR 2 billion per year. Based on a small (but growing) number of case studies that have assessed management effectiveness, it is clear that the cover of invasive alien plants has been reduced in some localised areas, but continues to grow in others. A number of factors contribute to success, but the effort and resources required for successful control appear to be routinely underestimated , with actual costs between 1.5 and 8.6 times higher than initial budget estimates. Currently, therefore, control measures (other than biological control) have largely failed to check invasions at a national scale, and there have been no documented eradications of plant invasions from continental South Africa. We argue that control can be considerably improved by effective prioritisation, goal-setting and planning; monitoring of outcomes rather than of inputs;

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Evaluating the efficacy of invasive plant control in response to ecological factors

Cited by 12 publications

References 36 publications

Contrasting impacts of an alien invasive shrub on mammalian savanna herbivores revealed on a landscape scale

Contrasting impacts of an alien invasive shrub on mammalian savanna herbivores revealed on a landscape scale

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

The Extent and Effectiveness of Alien Plant Control Projects in South Africa

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