Control Of Invasive Alien Plants Research Articles

Passive restoration of fynbos after afforestation with exotic pines, South Africa

Plantations, and associated invasions, of exotic Pinus trees occur extensively in the southern hemisphere, threatening the persistence of biodiverse Mediterranean‐climate vegetation. Large‐scale decommissioning of such plantations in the eastern Cape Floristic Region (South Africa) enabled a wide‐ranging study showing successful passive restoration of fynbos vegetation after afforestation. Using a paired study design, we compared the diversity, and floristic and growth‐form composition of post‐fire recovering fynbos in former plantations with that in recently burnt neighboring fynbos in a natural state within the Garden Route National Park. The fynbos of the study area showed good autogenic recovery after several decades of pine afforestation and a fire subsequent to the clearcutting of these trees. On average, native plant abundance and species richness (particularly of shrubs) were significantly lower, and non‐native plant species richness significantly higher, in former plantation areas than in natural fynbos, but these differences were small. Species diversity (Shannon–Wiener index) did not differ significantly between the two vegetation states. The former plantations harbored 91% of the number of native species that the natural fynbos had, while the similarity of the two floras was 65%. Non‐metric multidimensional scaling ordination and multivariate generalized linear models accordingly showed no clear distinction in community composition between the two vegetation states. We concluded that the restoration potential of the montane grassy fynbos in the study area is superior to that previously documented in montane proteoid fynbos, and that fire and invasive alien plant control after clearcutting of the plantations is essential to promote fynbos restoration.

Invasive alien plant control: The priority to save one of the most rapidly declining island-endemic plant species worldwide

Up to 6,800 plant species endemic to oceanic islands are highly threatened with extinction. Although habitat destruction and fragmentation have greatly contributed to this, it is generally recognised that invasive alien species currently pose the single most important threat to island plants. Most studies exploring the role of novel interspecific interactions in driving declines of island plants, focus on threats mediated by animals, be it direct (e.g. browsing, seed predation, mutualism disruption) or indirect (e.g. extinction of seed dispersal or pollination mutualists). Relatively few studies have investigated the specific role of plant-plant interactions, particularly in-situ. We studied a threatened island endemic plant in rapid decline to evaluate the short (1–2 years) and medium-term (about 1–2 decades) influence of invasive alien plants (IAPs) on individuals and a variety of proxies of plant fitness. We compared mortality of traceable individuals that were recorded 12–20 years previously between habitats that are invaded with IAPs and habitats where IAPs are absent, or have been removed decades ago. We also carried out an in-situ manipulative experiment using 14 randomly chosen plants from around which IAPs were removed, paired with controls, at two sites. Canopy cover change before and after IAPs’ removal was quantified along with above ground biomass of IAPs removed for use as potential explanatory variables of change in proxies of plant fitness. Ten branches were randomly selected per plant and branch dynamics, leaves’ sizes and reproductive structure production were monitored quarterly for two years. Over the medium term, plant mortality was recorded only in presence of IAPs (X2 = 4.80, df = 1, p < 0.05). Over the short term, at the plant level, IAPs’ removal triggered overall weak to moderate improvements in the number of surviving and new branches as well as change in number of branches at one of the sites. At the leaf and branch levels, we found weak evidence for positive effects of IAPs removal on surviving leaves, flower buds produced and difference in leaf surface area per branch in one site. We therefore provide some experimental evidence of negative effects of alien plants on overall fitness of the threatened species in-situ presumably through competitive interactions. We posit that these effects were found to be weak to moderate due to the short experimental period over which they could develop (1–2 years). Overall, IAPs stand out as the most severe threat from among all documented threats to the species, for being the only one capable of causing mortality of adult plants. Results hence highlight island plants’ vulnerability to IAPs, and how their timely control would improve the survival and fitness of threatened plants, even at the scale of single individuals. Such a strategy could be more often employed. Our study stresses on prioritising IAPs’ control for rescuing long-lived threatened plants that grow in habitats invaded by alien plants (itself a very common situation on oceanic islands) before addressing other subtler, slower-acting threats, like disrupted pollination or seed dispersal mutualisms, florivory or seed predation.

A review of two decades of government support for managing alien plant invasions in South Africa

Large sums of money are spent globally on invasive alien plant control projects, but their effectiveness in the medium to long term is seldom reported. Here we review the cost, extent and effectiveness of the management of plant invasions by South Africa's “Working for Water” program between 1998 and 2020. We use a broad framework of indicators for assessing the inputs, outputs, and outcomes of alien plant control interventions at a national level. Our study is based on (1) spatially explicit data on efforts that targeted selected sites and species for control; (2) surveys of the extent of invasion; and (3) case studies of control effectiveness. An average of ZAR310 million (adjusted to 2020 values) was spent annually, creating the equivalent of 8113 full-time jobs, with expenditure rising rapidly between 1998 and 2003 and again between 2009 and 2015, dropping more recently. Control efforts were directed at 178 species, with 15 taxa receiving two thirds of the total expenditure. Control was conducted on ~76,000 sites covering 2.7 million ha, which is ~14 % of the estimated invaded area. Over a quarter of the control was not in priority areas for biodiversity and/or water conservation. The effectiveness of control operations has not been monitored regularly, but a few studies at local scales have found reductions in alien plant cover, and it is likely that “Working for Water” has had a role in limiting invasion. Nonetheless, national surveys suggest that plant invasions have continued to grow—the problem is too large to expect that control can be achieved everywhere. We recommend that, to bring plant invasions under control at priority sites, a national strategy should be based on conservation triage, focussing on clearly defined priority sites, improving planning and monitoring, and increasing operational efficiency.

Nitrogen isotopes of Eichhornia crassipes (water hyacinth) confirm sewage as leading source of pollution in Hartbeespoort Reservoir, South Africa

Nitrogen (N) isotopes of aquatic organisms offer a way of differentiating sources of dissolved nitrate species in water. Water quality in the Hartbeespoort Reservoir has been a problem for many decades, causing excessive growth of algae and water hyacinth, both of which further cause human health issues, degradation of environmental water quality, and recreational hazards. Six boreholes and four surface water locations were sampled and analysed for certain water quality parameters and stable water isotopes (H and O). Electrical conductivity and pH were acceptable, but faecal coliforms and Escherichia coli were high in the Crocodile River. δD and δ18O showed that there is little groundwater input to the reservoir and the surface water experiences significant evaporation. Six samples of water hyacinth were analysed for C and N stable isotopes. The δ15N values ranged from 20‰ to 33‰, indicating sewage or manure as the primary source of dissolved N in Hartbeespoort Reservoir. As high dissolved N concentrations cause water hyacinth growth to outstrip any manual, chemical or biological control measures, it is suggested that efforts to control the water hyacinth infestation on Hartbeespoort Reservoir focus on informal settlement sanitation and upgrades to sewage treatment works in the Crocodile River catchment. Significance: This work is possibly the first report on nitrogen isotopes in plant material to trace water pollution in South Africa. It presents a new line of evidence regarding eutrophication in the Hartbeespoort Reservoir. It indicates the optimal management method for controlling water hyacinth on this and other waterbodies. The study has relevance for agriculture, urban wastewater management, informal settlement sanitation, invasive alien plant control, recreation and tourism.

Plant Pathogens and Biological Control of Invasive Alien Plants in South Africa: A Review of Projects and Progress (2011–2020)

The use of plant pathogens for biological control (biocontrol) of invasive alien plants in South Africa was reviewed in 1991, 1999 and 2011. In this review, subsequent progress and projects undertaken in the years 2011 to 2020, on both classical agents using exotic pathogens and inundative agents using indigenous pathogens, are detailed. We report on the impact of several previously introduced exotic fungi, monitored during this period. A significant highlight is the completion of 30 years of annual monitoring, from 1991 until 2020, of the impact of Uromycladium morrisii Doungsa-ard, McTaggart, Geering & RG Shivas (Raveneliaceae) on the density of Acacia saligna (Labill.) Wendel (Fabaceae), with declines of up to 98% recorded at monitored sites. Post-release monitoring also suggested that Entyloma ageratinae R.W. Barreto & H.C. Evans (Entylomataceae), introduced when Ageratina riparia (Regel) R.M.King & H.Rob (Asteraceae) still had a very limited invaded range in South Africa, has prevented the weed from realizing its potential as an invader. Uromycladium woodii Doungsa-ard, McTaggart, Geering & R.G. Shivas (Raveneliaceae) has been established on Paraserianthes lophantha (Willd.) I.C.Nielsen (Fabaceae), as has Puccinia xanthii Schwein (Pucciniaceae) on Parthenium hysterophorus L. (Asteraceae). Prospodium transformans (Ellis & Everh.) Cummins (Raveneliaceae) failed to establish on Tecoma stans (L.) Juss ex Kunth var. stans (Bignoniaceae), while efforts to release Puccinia lantanae Farl. (Pucciniaceae) on Lantana camara L. (Verbenaceae) are underway. Of the established exotic pathogens that are classical biocontrol agents, two are considered to cause extensive damage, two considerable damage, and two moderate damage, to their target weeds. Puccinia arechavaletae Speg. (Pucciniaceae), an adventive fungus that is established on Cardiospermum grandiflorum Sw. (Sapindaceae) following an unknown path of introduction, is proving to be a damaging agent and the implications of its presence in the country are discussed. Early season augmentation of Puccinia eupatorii Dietel (Pucciniaceae) on Campuloclinium macrocephalum (Less.) DC. (Asteraceae) was tested to determine whether damage could be increased, but no difference in the rust's incidence and severity was evident between augmented and naturally infected plants at the end of the growth season. The identity of the indigenous fungus registered as Stumpout®, for the control of coppice growth after felling of Acacia mearnsii De Wild. (Fabaceae), was confirmed as Cylindrobasidium torrendii (Bres.) Hjortstam (Physalacriaceae) rather than C. laeve (Pers.: Fr.) Chamuris, as previously thought. The application of another indigenous fungus, Colletotrichum acutatum J.H. Simmonds (Glomerellaceae), by means of helicopter flights has facilitated its establishment on Hakea sericea Schrad. & J.C. Wendl (Proteaceae), in inaccessible mountainous terrain. For registration purposes, toxicity testing (oral rat LD50) of these indigenous fungi are required. Lethal doses of Cylindrobasidium torrendii, C. acutatum and Pseudolagarobasidium acaciicola Ginns (Phanerochaetaceae), the latter for use against Acacia cyclops G. Don. (Fabaceae), exceeded 2000 mg kg–1 body weight and all three fungi are thus considered safe for application.

An Introduction to the Fourth Decadal Review of Biological Control of Invasive Alien Plants in South Africa (2011–2020)

This special issue is the fourth decadal review of biological control of invasive alien plants (biocontrol of weeds) in South Africa, following those published in 1991, 1999 and 2011. Including this introduction, there are 24 papers covering the weed biocontrol programmes, or important developments in the science and practice, from the period 2011-2020. Seventy-two target weed species are covered, including 25 species on which projects were initiated during the past decade. Developments in regulations, mass-rearing and implementation, and community engagement are also reviewed. An updated catalogue of agents released, rejected and under consideration is presented and reflects the most recent methods of quantifying success in weed biocontrol. Key events over the last decade include the hosting of the XIV International Symposium on Biological Control of Weeds to celebrate 100 years of weed biocontrol in South Africa, as well as the establishment of the Centre for Biological Control at Rhodes University. The science and practice of weed biocontrol has expanded significantly in the past decade, with growth in the number of researchers and practitioners, increased funding, and an increased number of scholarly outputs. Unlike many other countries in the world, South Africa has largely avoided constraints due to restrictive and risk averse legislation and bureaucracy, and has continued to release new biocontrol agents at a similar rate to that in previous years. Much of the success of weed biocontrol in South Africa is due to the sustained and increasing support of the Natural Resource Management Programme of the Department of Forestry, Fisheries and the Environment (Working for Water Programme). However, gaps in funding, where no funds are available for months at a time, are a major concern as the weed biocontrol community loses human capital in these periods, and research programmes suffer significant set-backs. Weed biocontrol is an essential component of South Africa's strategy to reduce the negative impacts of invasive alien plants and has contributed significantly towards the protection of the country's ecosystems, indigenous biodiversity, water security, agricultural productivity, and society in general. If the trend of increasing support for weed biocontrol in South Africa continues, we can expect that the benefits for the country at large will increase substantially in the future.

Editorial December 2021

This issue of the EPPO Bulletin shows an important part of the work of EPPO; Regional Standards in the area of phytosanitary regulation to control invasive plant pests. These Standards have been developed by experts in EPPO Panels, were extensively discussed, comments received from EPPO countries were considered and, in the end, the Working Party approved the Standards and the EPPO Council endorsed them. This process is facilitated by the EPPO Secretariat but relies on contributions of experts from EPPO’s member countries and ensures that the Standards are implementable, reflect reality, support NPPOs and thereby contribute to a harmonized way of working. The EPPO Council approved in September 2021 too many Standards to have them all published in this issue of the Bulletin. The EPPO Standards on efficacy evaluation of plant protection products in the PP1 series and three PM8 Standards on commodity-specific measures for forestry species, approved by Council this year, will be published in the April 2022 issue of the Bulletin. These Standards are available via online early view at https://onlinelibrary.wiley.com/toc/13652338/0/0. Moreover, EPPO’s Annual Report for 2020 in English is included, while the versions in French for 2020 and 2019 are available on the EPPO website, describing the whole range of EPPO’s work. The EPPO Standards in this issue include amongst others pest-specific Diagnostic Protocols, Standards for quality management and accreditation of laboratories, Standards on inspection of places of production and consignments of specific commodities and, a Standard on reducing the risk of soil from processing factories for potato cultivation. This latter Standard illustrates clearly how growers, processors and National Plant Protection Organizations (NPPOs) can take their respective responsibility and can work together to reduce risks of returning soil to farms. The role of NPPOs remains crucial. Another interesting subject is covered by the new Standard in the PM5 series on the design and implementation of a buffer zone to minimize the probability of spread of a pest into or out of regulated areas. This Standard gives guidance to risk assessors and risk managers to assess what size of buffer zone is matching their needs and possibilities. Moreover, a revision on the Standard on biological control agents, to clarify the criteria to list biological control agents safely used in the EPPO region, and Standards on control of invasive alien plants are included. The article on the developments in the work area of invasive alien plants over the past ten years in Europe gives a good overview of the work done in Europe on assessing, controlling, preventing and regulating IAP and the role EPPO played in this. Furthermore, this issue continues to contribute to pest reporting by including several reports on first findings which are important to signal new or changed risks, e.g. of the giant date mealy bug and the bay sucker in Jordan, Drosophila suzukii in the Russian Caucasus and scale insects and mealy bugs in Kenya. EPPO continues to work with many experts inside and outside the EPPO region to support NPPOs in their work to prevent the introduction and spread of pests and to control them. We have greatly appreciated the efforts of all experts to continue to contribute to EPPO’s work remotely due to COVID-19 restrictions. EPPO is, however, looking forward to working together during physical meetings in the near future. This will enhance the formal and informal discussions and exchange of information and EPPO can fulfil its role as a platform to experts to strengthen and enlarge their network.

An impact assessment tool to identify, quantify and select optimal social-economic, ecological and health outcomes of civic environmental management interventions, in Durban South Africa

Using an environmental impact assessment (EIA) methodology, we provide a novel approach to identify and assess social-ecological outcomes from civic ecology interventions. We quantified the impact significance of six civic (community led) interventions implemented by the Wise Wayz Water Care (WWWC) local community programme (solid waste management, water quality monitoring, invasive alien plant control, crop production, recycling and community engagement), in two communities, situated in urban to peri-urban/rural environments in Durban, South Africa. Interventions resulted in 37 outcomes, of which 36 were positive and one negative. The resulting significance scores from the impact assessment allowed for interventions and their outcomes to be compared. The socio-economic outcomes were the greatest (21), followed by ecological (11) and health outcomes (6). Outcomes included access to education and training; improved quality of life; improved terrestrial and aquatic ecosystems; increase in recreation and cultural uses of natural areas; reduced health risks and increased nutrition. The most significant ecological outcomes resulted from invasive alien plant control, followed by solid waste removal and water quality monitoring. The greatest health outcomes resulted from solid waste removal and vegetable gardens, whereas the greatest social-economic outcomes resulted from the general operation of WWWC, solid waste removal, and invasive alien plant control. We demonstrate that investments in natural areas can deliver not only on enhancements in ecosystems and their services, but also for local community socio-economic and health benefits. This study provides an intervention quantifying tool for practitioners to select optimal local management interventions, that can be aligned with desired outcomes related to specific community challenges and policy requirements. In so doing, this work shows the critical role that civic interventions play to ensure sustainability, and emphasises how social-ecological systems and ecosystem services perspectives can be used in practice towards achieving sustainable outcomes.

Civic Ecology Uplifts Low-Income Communities, Improves Ecosystem Services and Well-Being, and Strengthens Social Cohesion.

Ecosystem services enhance well-being and the livelihoods of disadvantaged communities. Civic ecology can enhance social-ecological systems; however, their contributions to ecosystem services are rarely measured. We analysed the outcomes of civic ecology interventions undertaken in Durban, South Africa, as part of the Wise Wayz Water Care programme (the case study). Using mixed methods (household and beneficiary (community members implementing interventions) surveys, interviews, field observations, and workshops), we identified ecosystem service use and values, as well as the benefits of six interventions (solid waste management and removal from aquatic and terrestrial areas, recycling, invasive alien plant control, river water quality monitoring, vegetable production, and community engagement). Ecosystem services were widely used for agriculture, subsistence, and cultural uses. River water was used for crop irrigation, livestock, and recreation. Respondents noted numerous improvements to natural habitats: decrease in invasive alien plants, less pollution, improved condition of wetlands, and increased production of diverse vegetables. Improved habitats were linked to enhanced ecosystem services: clean water, agricultural production, harvesting of wood, and increased cultural and spiritual activities. Key social benefits were increased social cohesion, education, and new business opportunities. We highlight that local communities can leverage natural capital for well-being and encourage policy support of civic ecology initiatives.

Invasive alien plant control improves foraging habitat quality of a threatened island flying fox

Flying foxes play keystone ecological roles in plant reproduction. Yet, they face numerous threats, including persecution for eating commercial fruits. This human-wildlife conflict has recently escalated to culling campaigns of a threatened flying fox on Mauritius. Finding non-lethal solutions to this human-wildlife conflict on the island is therefore extremely important. We hypothesized that invasive alien plants may reduce native fruit availability through competition and that weeding alien plants could improve the native foraging habitat quality of flying foxes – in turn, reducing their consumption of commercially important fruits. We compared native fruit production and foraging intensity of the Mauritian flying fox (Pteropus niger) in forests weeded of alien plants a decade previously and adjacent non-weeded forests. Fruits and ejecta were collected weekly during five months under 144 randomly chosen native trees of two canopy species whose fruits are eaten by flying foxes. Intraspecific variations in tree and fruit traits were used to examine flying fox foraging preference. Native fruit production was significantly higher in weeded forests for both tree species, and this was matched by higher flying fox foraging intensity. Flying foxes preferred large trees and fed predominantly on large and ripe fruits. The predominant consumption of ripe fruits emphasizes the importance of flying foxes as seed dispersers. Our results indicate that alien plant invasion substantially reduces native fruit production and that weeded forests provide a much better habitat for flying foxes. Our findings lend support to invasive alien plant control as a management strategy in mitigating such human-wildlife conflicts.

Quantifying the social and economic benefits of the biological control of invasive alien plants in natural ecosystems.

Invasive alien plants reduce ecosystem service delivery, resulting in environmental, economic and social costs. Here we review the returns on investment from biological control of alien plants that invade natural ecosystems. Quantifying the economic benefits of biological control requires estimates of the reductions in ecosystem goods and services arising from invasion. It also requires post-release monitoring to assess whether biological control can restore them, and conversion of these estimates to monetary values, which has seldom been done. Past studies, mainly from Australia and South Africa, indicate that biological control delivers positive and substantial returns on investment, with benefit:cost ratios ranging from 8:1 to over 3000:1. Recent studies are rare, but they confirm that successful biological control delivers attractive returns on investment, which increase over time as the value of avoided impacts accumulates.

The impact of data precision on the effectiveness of alien plant control programmes: a case study from a protected area

Successful long-term invasive alien plant control programmes rely on alien plant distribution and abundance data to assess, prioritise, implement and monitor the efficacy of the programme. Here we assess the impact of data accuracy using the alien plant programme in Table Mountain National Park, South Africa. A systematic plot-based survey method was carried out to assess the distribution of alien plants in the park at a fine scale (systematic sampling). Alien plant richness, total area invaded and the degree of spatial overlap in species’ presence were compared between the systematic sample and a protected area (PA) managers’ dataset (collated from collective observations by park visitors, rangers and managers) and Working for Water (WfW) project data (data collected for the planning and implementation of the alien plant clearing programme) using a range of confusion matrix-based statistics to assess similarity and error rates between the datasets. A total of 106 alien plant taxa were detected across the three datasets, 12 in PA manager’s data, 23 in WfW data and 101 in the systematic survey. Overall, there was substantive disagreement between the datasets on the distribution of alien plants. For example both management datasets estimated species’ hectare coverage at orders of magnitude greater than indicated by systematic sampling. The inaccuracy of manager data has direct negative implications for funding allocation, which currently appears to be in excess of what is required. We recommend that contrary to perception, fine-scale surveys are a cost-effective way to inform long-term monitoring programmes and improve programme effectiveness.

The invasive alien plants threatened the balance of ecosystem in conservative area in Ontoloe Island, Flores-Indonesia

Invasive alien plants threaten to biodiversity, particularly in small island with high endemicity values such as Ontoloe Island, a tourist destination area of Riung Seventeen Island in Flores. The study aims to characterized the invasive plants have attacked the conservative area in Ontoloe Island. The method used by combining the line method and the plot method with three observation stations in utilization block and four observation station in protection block. Plot of 1mx1m was used for the observation of ground cover plants and seedling, 5mx5m for the observation in stake level, 10mx10m for the observation in pole level, 20mx20m for the observation in tree level. The data level of the plants obtained then analyzed with Important Value Index (IVI). Result showed that Lamtoro plants (Leuchaena leucocephala) is the invasive alien species which has the highest IVI in both of utilization block and protection block in each level of tree, stake, and pole. There are other invasive alien plants such as Tembeleken (Lantana camara) and Bidara (Zizipus mauritiana) dominated in stake level and Alang-alang (Imperata cylindrica) dominated in seedling level. All the native plants in Ontoloe Island will be threatened their existing because of the less control of invasive alien plants. Therefore, needs serious handling by the government in order to keep the balanced of the ecosystems in Ontoloe Island to be maintained especially to not deviated from management objectives area of Komodo Dragons conservation (Varanus komodoensis Ouwens, 1912).

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

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. 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.

Assessing the status of biological control as a management tool for suppression of invasive alien plants in South Africa

Background: Biological control of invasive alien plants (IAPs) using introduced natural enemies contributes significantly to sustained, cost-effective management of natural resources in South Africa. The status of, and prospects for, biological control is therefore integral to National Status Reports (NSRs) on Biological Invasions, the first of which is due in 2017. Objectives: Our aim was to evaluate the status of, and prospects for, biological control of IAPs in South Africa. We discuss expansion of biological control and suggest indicators to be used in the upcoming NSR to assess sufficient growth. Method: We used published literature, unpublished work and personal communication to assess the status of biological control of IAPs. We propose indicators based on the targets for biological control that were proposed in the 2014 ‘National Strategy for dealing with biological invasions in South Africa’. To prioritise targets for future efforts, we used published lists of damaging IAPs and assessed the prospects for their biological control. Recommendations for using biological control as a management tool were made after discussion among the authors and with colleagues. Results: Significant control of several Cactaceae, Australian Acacia species and floating aquatic plants, and many other IAPs has been achieved in South Africa since 1913. Recently, biological control has benefited from improved international collaboration, a streamlined application process for the release of new biological control agents (resulting in the approval of 19 agents against 13 IAP species since 2013), and increased funding and capacity. There is still a need to improve implementation and to better integrate biological control with other control methods. In order to maximise benefits from biological control, increased investment is required, particularly in implementation and post-release evaluation, and in targeting new IAPs. Proposed targets for growth between 2017 and 2020 include an increase in financial investment in research by 29%, implementation by 28% and mass-rearing by 68%. Research capacity should increase by 29%, implementation capacity by 63% and mass-rearing capacity by 61%. New research projects should be initiated on 12 new IAP targets, while post-release monitoring efforts should be expanded to another 31 IAPs. Conclusion: Biological control of IAPs has contributed substantially to their management in South Africa, and continues to do so. Further investment in targeted aspects of IAP biological control will increase this contribution.

Long‐term declines of native trees in an oceanic island's tropical forests invaded by alien plants

AbstractQuestionHow did the native and alien woody plant communities of protected lowland wet forests of a tropical oceanic island change in the presence of understorey invasive alien plants over the medium (21–27 yrs) and longer term (68 yrs)?LocationBel Ombre, Brise Fer and Macchabé forests in the Black River Gorges National Park (BRGNP), Mauritius (20°22′10″–20°28′17″ S, 57°24′45″–57°27′12″ E).MethodsRandom and replicated vegetation plots were sampled in two protected forest areas whose communities of woody plants were surveyed 21 and 27 yrs previously, and in another protected and similar forest that was surveyed 68 yrs earlier, to identify species and measure stem diameters so as to permit comparisons at the three sites over these time periods.ResultsInvasion by woody alien plants has progressed through time at all three sites, comprised mostly of the understorey and shade‐tolerant Strawberry guava (Psidium cattleianum). Concomitantly, although reductions in native woody plant species richness of large trees (≥10 cm DBH) were not statistically significant at the community level, their densities and basal area had roughly halved in 68 yrs. Comparisons with the studies 21–27 yrs previously confirmed the tendency towards a reduction in density of larger trees, besides indicating a trend towards decline in species richness of smaller understorey trees.ConclusionAn unabated replacement of native by alien trees over the longer term is occurring in protected areas of the lowland wet forests of the BRGNP and presumably in other similarly invaded areas. Our work stresses the importance of long‐term monitoring in elucidating impacts of invasive alien plants at the community level, particularly when dealing with slow‐growing and long‐lived species. Plausible mechanisms bringing about the observed changes and that have been found at the same or similar sites, include reduced regeneration, growth, production of flowers and fruits and increased mortality of native trees when these grow among invasive alien plants. The control of invasive alien plants, where they invade tropical forests, should be a central conservation objective even in better preserved and well protected areas.

Ecological research and conservation management in the Cape Floristic Region between 1945 and 2015: History, current understanding and future challenges

In 1945, the Royal Society of South Africa published a wide-ranging report, prepared by a committee led by Dr C.L. Wicht, dealing with the preservation of the globally unique and highly diverse vegetation of the south-western Cape. The publication of the Wicht Committee’s report signalled the initiation of a research programme aimed at understanding, and ultimately protecting, the unique and diverse ecosystems of the Cape Floristic Region. This programme has continued for over 70 years, and it constitutes the longest history of concerted scientific endeavour aimed at the conservation of an entire region and its constituent biota. This monograph has been prepared to mark the 70th anniversary of the Wicht Committee report. It provides a detailed overview of the circumstances that led up to the Wicht Committee’s report, and the historical context within which it was written. It traces the development of new and substantial scientific understanding over the past 70 years, particularly with regard to catchment hydrology, fire ecology, invasive alien plant ecology, the harvesting of plant material and conservation planning. The Wicht Committee’s report also made recommendations about ecosystem management, particularly with regard to the use of fire and the control of invasive alien plants, as well as for the establishment of protected areas. Subsequently, a combination of changing conservation philosophies and scientific conservation planning led to the creation and expansion of a network of protected areas that now covers nearly 19% of the Cape Floristic Region. We also review aspects of climate change, most of which could not have been foreseen by the Wicht Committee. We conclude that those responsible for the conservation of these ecosystems will face many challenges in the 21st century. These will include finding ways for effectively managing invasive alien plants and fires, as foreseen by the Wicht Committee. While the protected area network has expanded beyond the modest targets proposed by the Wicht Committee, funding has not kept pace with this expansion, with consequences for the ability to effectively manage protected areas. The research environment has also shifted away from long-term research conducted by scientists embedded in management agencies, to short-term studies conducted largely by academic institutions. This has removed a significant benefit that was gained from the long-term partnership between research and management that characterised the modis operandus of the Department of Forestry. Growing levels of illegal resource use and a changing global climate also pose new challenges that were not foreseen by the Wicht Committee.

100 years of biological control of invasive alien plants in South Africa: History, practice and achievements

On 26 June 1906, the fourth Parliamentary Select Committee on Agricultural Cooperation met in Cape Town to debate the apparently intractable scourge to agriculture, and the wider community, of dense infestations of sweet prickly pear (Opuntia ficus-indica) in the Eastern Cape and Karoo. Originating from Central America, this plant had been in South Africa since at least the 1750s, and by the 1890s had invaded an estimated 314 000 ha, which increased to about 1 million ha by the 1950s. Dr G.H. Maasdorp, a member of the Legislative Assembly of the Cape and a medical practitioner in Graaff-Reinet, which was literally in the thick of the prickly pear problem at the time, presented his perceptive views to the Committee.

English

In this study, we investigated three different treatment options for controlling infestations of the aggressive Invasive Alien Plant Species (IAPS)&nbsp;Lantana camara&nbsp;at the Emantini Game Reserve in Swaziland. Treatment options included cut stump treatment, foliar spraying with herbicide and hand pulling using a manual plant puller. Results from this study indicated that foliar spraying significantly reduces new growth compared to other treatment options investigated. Associations between the various treatments and regrowth were not significant. Comparisons of the various treatments using a contribution index (CI) showed that foliar spraying is the most effective overall treatment for controlling&nbsp;L. camara&nbsp;at our study site. Foliar spraying worked best on plants less than 1.5 m high, but cut stump treatment was most effective for thickets where plants needed to be cut before being treated. To improve the effectiveness of foliar spraying, we suggest that this treatment option be used in combination with cut stump treatments. Findings from this study provide valuable information for the control of&nbsp;L. camara&nbsp;in different growth stages and levels of infestation. Recommendations for the control of this IAPS can be used in similar environments to effectively control infestations. &nbsp; Key words:&nbsp;Invasive alien plant control, invasive alien plant species (IAPS),&nbsp;Lantana camara, Swaziland.

The Challenges of Alleviating Poverty through Ecological Restoration: Insights from South Africa's “Working for Water” Program

AbstractPublic works programs have been posited as win–win solutions for achieving societal goals for ecological restoration and poverty alleviation. However, little is documented regarding the challenges of implementing such projects. A commonly cited example is South Africa's invasive alien plant control program “Working for Water” (WfW), which aims to create employment via restoring landscapes invaded with alien plants. Recent studies have raised questions over the effectiveness of this program in achieving both its restoration and poverty alleviation goals. This is the first study that we are aware of that synthesizes the knowledge of managers on both the poverty alleviation and environmental outcomes of a public works project. Herein, we sought to understand the challenges and constraints faced by 23 WfW managers in fulfilling the program's environmental and poverty alleviation objectives. We found that the challenges most frequently cited by managers related to the capacity and competence of managers and teams, followed by challenges relating to planning and coordination, specifically the challenges of being flexible and adaptive when constrained by operating procedures. In addition, the current focus on maximizing short‐term employment was perceived by some as limiting the efficiency and long‐term effectiveness of the WfW program in achieving its environmental and social goals. We suggest that improving the conditions and duration of employment could improve the effectiveness of invasive alien plant control and ecological outcomes. We also suggest that WfW measure the impacts of their interventions through an adaptive management approach so that it can learn and adapt to the challenges it faces.