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Ecological infrastructure (EI) is a natural and near-natural functioning ecosystem that delivers a range of essential services to humankind. Examples include mountain catchments, wetlands, coastal dunes, and riparian corridors. In a world where EI is underinvested, rapid degradation and threats such as unsustainable veld-fire regimes, droughts, climate change, and invasive alien plants persist in dominating the ecological landscape. In South Africa, there are government programmes that encourage the restoration, rehabilitation and protection of EI. However, inadequate funding allocations constrain scaling-up and thus necessitate the unlocking of public and private sector investments to augment resources for ecosystem-based management interventions. A systematic literature review was conducted at a global scale to (1) understand the drivers behind EI investments, (2) understand the willingness and desire of private landowners and land users to participate and contribute to EI investments and (3) identify institutional support mechanisms used to encourage investments. Results suggest that the need to invest is driven by growing degradation of EI and the urgency to meet environmental sustainability goals. The willingness to invest is stimulated by the use of economic-based policies and compensatory mechanisms. Public-private partnerships, public policy, and market-based conservation instruments are institutional arrangements executed to protect EI. These include processes and systems used by the institutions to legislate and manage interventions towards fulfilling the conservation objective. Our review contributes to the EI investment research agenda by recommending coordinated efforts to encourage EI investment from both public and private partners. These measures will help to secure financial resources and mobilise investments beyond monetary terms by coordinating planning and developing capacity and reform policies. Significance: * Reviewing international experiences on ecological infrastructure investments will help to inform the Natural Resources Management programmes' efforts to upscale the investments essential to conserve natural ecosystems. The lessons from the systematic review will further reveal other related natural ecosystem investment processes from which to learn, Therefore, gaining a global understanding of these lessons provides evidence-based advice for policy development and decision-making processes which seek to protect natural ecosystems for present and future generations. [ABSTRACT FROM AUTHOR]

Invasive alien plants negatively impact ecosystems, necessitating intricate management actions. In a critically endangered vegetation type within the fynbos biome of South Africa, a study was performed comparing different management interventions over plots invaded by Acacia saligna. A dynamic modeling approach was designed to analyze field data and simulate the effectiveness of several restoration methods. Field data for vegetation recovery rates over the course of 2 years were fed into the model, which allowed the extrapolation of multiple recovery trajectories over a long time‐span, not possible to obtain from traditional short‐term field surveys. Our model simulations show that different treatments in similarly degraded states at the time of clearing can result in vastly different recovery trajectories. Active seed sowing was initially most expensive but resulted in the most successful native shrub recovery, decreasing costs of longer‐term follow‐up acacia clearing. Clearing without burning was cheapest but resulted in limited establishment of both native and acacia cover, providing an opportunity for secondary invasion by alien forbs. In this case, biotic thresholds may have been crossed which prevented recovery of certain vegetation components. Active sowing can partially reverse thresholds by restoring shrub cover but not structural diversity. Therefore, even applying this treatment did not resemble vegetation structure of the reference condition after an extended period of 30 years, but does show how restoration can be improved by native seed sowing compared to passive restoration alone. Our model simulations provide a useful tool to support decision‐making by providing management recommendations for optimizing alien plant‐clearing protocols. [ABSTRACT FROM AUTHOR]

The negative impact of invasive alien plants (IAPs) in protected areas (PAs) is managed through control programmes, often using area‐based management, where identified IAPs in management units are controlled simultaneously. However, this approach has shortfalls, including the methods used to prioritise management units, spatial grain dependence and spatial interdependence of management units. Species‐based management approaches, though used less frequently, are usually aimed at eradication.We propose using a Commonness framework to reconcile area‐based and species‐based management approaches, viewing the invasion process as a population trajectory from uncommon to common. The framework assigns species to one of eight commonness types at a given scale using three species characteristics: local population size (small/large), geographic range (wide/narrow) and spatial pattern (even/clumped). These metrics were calculated using a comprehensive fine‐scale IAP dataset from Table Mountain National Park, South Africa, at six scales of increasing spatial grain, enabling quantification of the effects of scale and species' range structure on management potential of IAPs.Most species exhibited the Point Source commonness type at fine spatial grains, requiring Rapid Response, Reconnaissance or Sweeping management strategies. At coarser grains, species were mostly classed within wide occupancy ranges, with small population sizes (Dispersed and Sparse types). The Control strategy currently applied in the area (best suited for large populations across a narrow range) should be re‐evaluated given the progress made by historical clearing in reducing commonness. Using a phylo‐tree, we identified adjacent areas that require different strategies as well as changes in species‐specific goals at particular sites with increasing grain coarseness. For example, species generally deemed to be common, for which a Control strategy is applied, may require Rapid Response type strategies for isolated and/or small, clumped subpopulations.Synthesis and applications. We use a Commonness framework to quantify patterns of plant invasion at multiple spatial scales. We demonstrate how different management strategies are appropriate for the same species in different parts of its invaded range, and how these nuances are often obscured through the use of coarse data. The framework enables tailoring management interventions to minimise the spread and impact of invasive alien plants. [ABSTRACT FROM AUTHOR]

Ecological restoration is a global imperative to reverse widespread habitat loss and degradation, including by invasive alien plants. In South Africa's Core Cape Subregion, alien tree invasions are widespread and their control continues to be a major undertaking. As funding is limited, active restoration interventions are rarely implemented and the focus is on invader removal – the assumption being that ecosystems will self-repair. This paper reviews research findings from the past three decades to assess in which situations spontaneous succession is a viable strategy for restoring alien-invaded ecosystems. We found that ecosystems can self-repair, provided that key biotic and/or abiotic thresholds have not yet been crossed. Self-repair has been observed in many cases where dense invader stands with short residence times have been cleared and where diverse native plant growth forms survive, either in the above-ground vegetation or in soil seed banks. However, several factors influence this generalisation, including the identity of the invader, the ecosystem type, and the efficacy of alien control. Thresholds are crossed sooner with invasions of alien Acacia and Eucalyptus species than those of Hakea and Pinus species, resulting in lower potential for spontaneous recovery. Lowland fynbos ecosystems are less resilient to invasion, and have a lower capacity for self-repair, than mountain fynbos ecosystems. Poorly implemented alien plant control measures can result in a resurgence of the invader to the detriment of native species recovery. We outline some management principles for optimising spontaneous succession potential and integrating alien control and restoration interventions. [ABSTRACT FROM AUTHOR]

Addressing complex challenges facing social-ecological systems (SES) requires the integration of knowledge from a diversity of disciplines and stakeholders. This requirement has resulted in the establishment of many integrative research programmes, both globally and locally, aimed at coproducing knowledge relevant to solving SES challenges. However, despite the increase in integrative projects, there has been little research on the nature and extent to which these projects acknowledge and integrate information from diverse disciplines or knowledge types. In this study, we explored the extent to which the integration of different disciplines has occurred, using a case study of the South African invasive species management programme, Working for Water (WfW). Here we provide an overview of the research produced under the auspices of WfW, and how it came to be. Additionally, we assess the extent to which research associated with the programme addressed the research priorities and how these priorities relate to one another. Findings show that WfW-associated research is primarily focused on the ecological processes and impacts associated with invasive alien plants and biological control. Social science and applied research are, however, under-represented, infrequent in nature and inadequately address the research priorities set in the programme. To address these shortcomings, we recommend the development of a detailed research strategy and action plan conducive to integrative research and transdisciplinary collaboration, and relevant to solving complex SES challenges such as those associated with biological invasions. Significance: * We provide a reference point by which we can assess research progress and guide integration of diverse knowledge systems. * The results can help guide research decision-making as it relates to invasive species management. [ABSTRACT FROM AUTHOR]

Invasive alien plants impact ecosystems, which often necessitates their removal. Where indigenous species recovery fails following removal alone, an active intervention involving reintroduction of seed of native species may be needed. This study investigated the potential for a combination of the fire cues of smoke and heat as a pre-treatment of seeds in breaking dormancy and facilitating increased germination. Species were selected to represent different functional types within Cape Flats Sand Fynbos; a fire-prone, critically endangered vegetation type in South Africa. Seeds were exposed to either a heat pulse (temperatures between 60 and 300°C for durations of between 30 s and 20 min) or dry after-ripening (1 or 2 months at milder temperatures of 45°C or less). Thereafter, seeds were soaked in smoke solution for 18 h and subsequently placed on agar at 10/20°C for germination. Most species fell into one of two main groups: Seed germination in the first group was greatest following a lower temperature (60°C) heat pulse, an extended period of mild temperature (20/40°C or 45°C) exposure, or no pre-treatment with heat. Seed germination in the second group was promoted after brief exposure to higher (100°C) temperatures. No germination occurred in any species following heat treatments of 150°C or higher. Species which responded better to higher temperatures were mainly those possessing physical dormancy, but seed morphology did not correlate with germination success. This study showed that heat stimulation of seeds is more widespread in fynbos plant families than previously known and will enable the development of better seed pre-treatment protocols before large-scale sowing as an active restoration treatment after alien plant clearing. [ABSTRACT FROM AUTHOR]

The introduction of alien plants can influence biodiversity and ecosystems. However, its consequences for soil microbial communities remain poorly understood. We addressed the impact of alien ectomycorrhizal (EcM) pines on local arbuscular mycorrhizal (AM) fungal communities in two regions with contrasting biogeographic histories: in South Africa, where no native EcM plant species are present; and in Argentina, where EcM trees occur naturally. The effect of alien pines on AM fungal communities differed between these regions. In South Africa, plantations of alien EcM pines exhibited lower AM fungal richness and significantly altered community composition, compared with native fynbos. In Argentina, the richness and composition of local AM fungal communities were similar in plantations of alien EcM pines and native forest. However, the presence of alien pines resulted in slight changes to the phylogenetic structure of root AM fungal communities in both regions. In pine clearcut areas in South Africa, the richness and composition of AM fungal communities were intermediate between the native fynbos and the alien pine plantation, which is consistent with natural regeneration of former AM fungal communities following pine removal. We conclude that the response of local AM fungal communities to alien EcM pines differs between biogeographic regions with different histories of species coexistence. [ABSTRACT FROM AUTHOR]

The Nama-Karoo biome occupies 28% of South Africa’s land area. Alien leguminous trees of the genusProsopishave invaded large tracts of Nama-Karoo rangeland. We evaluated the impact ofProsopisinvasion and clearing on vegetation species composition and diversity (alien and indigenous species richness and cover) in Nama-Karoo rangeland on two sheep farms in the Beaufort West district of the Western Cape province of South Africa. Our results suggest thatProsopisinvasion and clearing can significantly change Nama-Karoo rangeland species composition. Invasion and clearing appear to have no effect on alien species richness. Invasion, however, increases alien species cover, while clearing restores it to pre-invasion levels. In contrast, invasion reduces indigenous species richness while clearing restores it to pre-invasion levels. Invasion appears to have no effect on indigenous species cover. This lack of effect appears to be the serendipitous result of a site-specific trade-off between a decline in cover of grasses that are negatively affected byProsopisinvasion and a concomitant increase in the cover of positively affected grasses. Clearing increases indigenous species cover to above pre-invasion levels. The higher than usual indigenous species cover after clearing could be a transient legacy ofProsopissoil nutrient enrichment. [ABSTRACT FROM AUTHOR]

The aim of our study is to provide an integrated framework for the management of alien plant invasions, combining insights and experiences from the fields of invasion and restoration ecology to enable more effective management of invasive species. To determine linkages between the scientific outputs of the two disciplines we used an existing data base on restoration studies between 2000 and 2008 and did a bibliometric analysis. We identified the type of restoration applied, determined by the aim of the study, and conducted a content analysis on 208 selected studies with a link to biological invasions (invasion-restoration studies). We found a total of 1075 articles on ecosystem restoration, with only eight percent of the studies having the main objective to control alien invasions. The content analysis of 208 invasion-restoration studies showed that the majority of the studies focused on causes of degradation other than alien invasions. If invaders were referred to as the main driver of degradation, the prevalent cause for degradation was invaders outcompeting and replacing native species. Mechanical control of alien plant invasions was by far the most common control method used. Measures that went beyond the removal of alien plants were implemented in sixty-five percent of the studies. Although invasion control was not as common as other types of restoration, a closer look at the sub-group of invasion-restoration studies shows a clear link between restoration and invasion ecology. Concerns, as identified in the literature review, are firstly that restoration activities mostly focus on controlling the invader while other underlying causes for degradation are neglected, and secondly that the current approach of dealing with alien invasions lacks a combination of theoretical and practical aspects. We suggest that closer collaboration between invasion and restoration ecologists can help to improve the management of alien plant invasions. We conclude with a framework and a case study from Perth Western Australia integrating the two disciplines, with the aim of informing restoration practice. [ABSTRACT FROM AUTHOR]

Conservation managers are required to make decisions in complex and uncertain contexts. To strengthen the robustness of conservation decisions, several approaches have been proposed to facilitate stakeholder engagement in the setting of conservation objectives and priority actions. While such processes have led to the formulation of several invasive alien plant management strategies to achieve specific objectives, the long-term consequences and trade-offs inherent in these strategies have not been tested. The performance of five of these strategies over 50 years was tested in the protected area context using empirical data from Table Mountain National Park, South Africa. A simulation model based on data for invasive Acacia species in a fire-driven ecosystem, focused on the interaction between strategy performance and clearing efficacy in achieving a management goal or reducing Acacia density to below 1 plant per hectare. At near perfect levels of clearing efficacy, all strategies converged towards reaching the management goal, while at lower efficacy levels the strategies diverged in their ability to achieve desired outcomes. Despite working across the largest area, strategies that focussed on clearing low density invasions, maintained the least area in a maintenance state over time. In contrast, strategies that focussed on a mix of post-fire, low density areas and high altitude areas cleared less area annually, but maintained a much larger area in a maintenance state. At higher levels of efficacy, strategies that return to previously worked areas were more successful than a post-fire strategy. Strategies that focused solely on securing water, performed poorly in maintaining low overall density of aliens. However, the influence of efficacy was significant and substantial and a much larger difference in area reaching the management goal was achieved by varying efficacy than varying strategy. As such, improving quality of work and implementation will have a far greater effect than which areas are prioritized or how this prioritization is done. While acacias are likely to persist in the long-term, improving work quality coupled with correct strategy selection will ensure continued gains in the area under maintenance and improved return on investment over time. • Infield clearing efficacy matters markedly more than area prioritisation strategy. • The strategy achieving highest success varied over time and with efficacy level. • When efficacy is known to be low, less area should be prioritized. • Outcome monitoring in invasive alien plant programmes is paramount. • Management quality and appropriate strategy reduces needs for increased funding. [ABSTRACT FROM AUTHOR]

It has been widely accepted that the biological control agents released on invasive Australian Acacia in South Africa, have impacted on the population dynamics of their host plants. However, there are no quantitative data to support these claims and these invasive species remain at similar abundance levels prior to the release of their associated biological control agents and also show evidence of range expansion. The effect of biological control agents, two bud galling wasps (Trichilogaster acaciaelongifoliae and T. signiventris) and one gall-forming rust fungus (Uromycladium morrisii), on the pod production of their respective hosts (Acacia longifolia , A. pycnantha and A. saligna) was assessed by quantifying the reproductive and galled trees per hectare as well as the pods and galls produced per tree and per square meter over a one to two year period. It was shown that invasive Australian Acacia satiate their gall-forming biological control agents, with many pods surviving in their presence. Pod production and loss was placed into perspective using recent findings of seed rain and seed bank studies. It was concluded, based on pod production, seed rain and seed bank data that despite T. acaciaelongifoliae , T. signiventris and U. morrisii reducing pod production, they have had no impact on the population dynamics of their invasive Australian Acacia hosts in South Africa. • Biological control impact on invasive Australian Acacia reproductive output tested for first time. • Invasive Australian Acacia satiate their gall-forming biocontrol agents, allowing pods to survive the pre-dispersal stage. • Gall abundance of biological control agents positively correlated with invasive host pod production. • Invasive Australian Acacia satiate their seed-reducing biological control agents. • Importance of testing hypotheses with field collected data to evaluate the accuracy of expert opinion illustrated. [ABSTRACT FROM AUTHOR]

• Active sowing results in successful establishment of native shrub cover and diversity. • Pre-treatment of seed can improve success of a restoration sowing intervention. • Passive restoration is seed limited, suggesting a biotic threshold has been crossed. • Invasive plant seedbanks are not more effectively depleted by burning after clearing. • A decision tree has been developed to determine best protocols for restoration based on site-specific characteristics. Invasive alien plants negatively impact ecosystems, but recovery of native vegetation may fail following standard methods of alien species removal alone. Alternative management actions may thus be required. Cape Flats Sand Fynbos is a critically endangered vegetation type in the Cape Floristic Region of South Africa which is threatened by Acacia saligna invasion, but standard clearing methods have failed to restore native vegetation structure. A restoration study was performed comparing passive treatments i.e. clearing without burning (stack-block) versus clearing and burning (burn-block), as well as active intervention by sowing seeds of native species, either initially after burning or a year later, in which seeds were either not pre-treated or pre-treated with smoke and heat exposure before sowing. After two years all treatments resulted in different recovery trajectories, although none resembled the reference condition. Clearing without burning facilitated recovery in less degraded areas with higher initial native shrub cover, but otherwise resulted in limited vegetation recovery. Limited recovery facilitated secondary invasion by herbaceous weeds. Active seed sowing resulted in the highest recovery of native shrub cover and diversity. These findings suggest that passive restoration is constrained by seed limitation, due to the lack of recovery of vegetation components under passive clearing treatment. Active sowing was able to partially overcome this constraint through improved recovery of total shrub cover. However, non-sprouting shrub cover was higher while resprouting shrubs and species of Restionaceae were lower compared to the reference condition. Pre-treatment of seeds before sowing improved establishment of some species. Active treatment involving sowing pre-treated seeds after clearing and burning therefore resulted in best fynbos recovery compared to either of the passive treatments tested. A decision tree has been developed based on these findings in order to guide best protocol for managers. [ABSTRACT FROM AUTHOR]