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Sustainability-focused research networks and communities of practice have emerged as a key response and strategy to build capacity and knowledge to support transformation towards more sustainable, just and equitable futures. This paper synthesises insights from the development of a community of practice on social-ecological systems (SES) research in southern Africa over the past decade, linked to the international Programme on Ecosystem Change and Society (PECS). This community consists of a network of researchers who carry out place-based SES research in the southern African region. They interact through various cross-cutting working groups and also host a variety of public colloquia and student and practitioner training events. Known as the Southern African Program on Ecosystem Change and Society (SAPECS), its core objectives are to: (1) derive new approaches and empirical insights on SES dynamics in the southern African context; (2) have a tangible impact by mainstreaming knowledge into policy and practice; and (3) grow the community of practice engaged in SES research and governance, including researchers, students and practitioners. This paper reflects on experiences in building the SAPECS community, with the aim of supporting the development of similar networks elsewhere in the world, particularly in the Global South. [ABSTRACT FROM AUTHOR]

Invasive alien species (IAS) are one of the most important factors driving extinction rates worldwide. Among the IAS, the impacts of introduced mammals on native biodiversity are most severe, with the European rabbit (Oryctolagus cuniculus) being the most problematic. Globally, European rabbits have been introduced to five continents and more than 800 islands or island groups where they are a threat to biodiversity and human livelihoods. The impacts of European rabbits on biodiversity and human livelihoods have been extensively studied across the globe. However, some regions of the world, such as the offshore islands along Africa's southern coast, have been sparsely studied. In this study, we monitored change in grazing capacity on a South African offshore island, Robben Island, following an attempt to eradicate European rabbits between 2008 and 2009. Grazing capacity on the island increased following rabbit control, driven by the recovery of palatable plant species in response to release from herbivory. There was no change in grazing capacity at sites under Eucalyptus plantations because of the inhibitory effects of the alien trees on understory vegetation dynamics. We believe that grazing capacity changes on Robben Island are indicative of potential vegetation changes on other southern African offshore islands. [ABSTRACT FROM AUTHOR]

Social-ecological systems (SES) research has emerged as an important area of sustainability science, informing and supporting pressing issues of transformation towards more sustainable, just and equitable futures. To date, much SES research has been done in or from the Global North, where the challenges and contexts for supporting sustainability transformations are substantially different from the Global South. This paper synthesises emerging insights on SES dynamics that can inform actions and advance research to support sustainability transformations specifically in the southern African context. The paper draws on work linked to members of the Southern African Program on Ecosystem Change and Society (SAPECS), a leading SES research network in the region, synthesizing key insights with respect to the five core themes of SAPECS: (i) transdisciplinary and engaged research, (ii) ecosystem services and human well-being, (iii) governance institutions and management practices, (iv) spatial relationships and cross-scale connections, and (v) regime shifts, traps and transformations. For each theme, we focus on insights that are particularly novel, interesting or important in the southern African context, and reflect on key research gaps and emerging frontiers for SES research in the region going forward. Such place-based insights are important for understanding the variation in SES dynamics around the world, and are crucial for informing a context-sensitive global agenda to foster sustainability transformations at local to global scales. [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]

The degree to which invasive Acacia species affect South Africa’s livestock production has received little attention. We investigated the ecological impacts of Acacia mearnsii invasion on forage quality and quantity and on soil resources, along A. mearnsii invasion gradients, on South African rangelands and the subsequent conditions following clearing. Grazing capacity was reduced by 72% in densely invaded sites, whereas clearing improved grazing capacity by 66% relative to densely invaded sites within 5 years. In densely invaded sites total grass species basal cover was reduced by up to 42%. As a result, A. mearnsii reduced grazing capacity, from 2 to 8 ha required to support one large stock unit (ha/LSU) in uninvaded and densely invaded sites, respectively. Soil moisture content was lower in densely invaded sites compared with lightly invaded and cleared sites. Plant litter increased from 1.3% to 4.2%, carbon content of the soil increased from 2.0% to 4.0% and nitrogen concentrations increased from 0.1% to 0.2% in response to invasion by A. mearnsii. Clearing resulted in improved grazing capacity within 5 years. These results also showed that, if left uncontrolled, wattle species can reduce livestock carrying capacity within montane grasslands in South Africa. EDITED BY James Aronson [ABSTRACT FROM AUTHOR]

The success of different rehabilitation treatments following surface mining on the arid west coast of South Africa was assessed. Treatments consisting of one or a combination of topsoil addition, plant translocation and seeding were applied to experimental rehabilitation sites in 2001, while the treatment of another site in 2008 combined all three techniques. Vegetation and species cover, species richness, diversity and evenness, and grazing capacity of rehabilitation sites were sampled during winter 2009 and summer 2010, and compared with a reference site. All rehabilitated sites achieved the objective to attain a minimum grazing capacity of 20 ha per small stock unit. Rehabilitation trials were successful in establishing a vegetation cover, but were unable to return species richness and diversity to reference levels and did not resemble the reference site in species composition. Common species in reference sites were absent or only occurred in low numbers. No treatment outperformed the others and further experimentation is needed to determine the most suitable combination. It is recommended that rehabilitation should be done in multiple stages in future to improve seedling survival and to return species that are unable to establish in the adverse conditions present at the onset of rehabilitation. [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 Nama-Karoo is the largest of the three biomes that comprise the semi-arid Karoo-Namib ecoregion of southern Africa. Large tracts of Nama-Karoo rangeland have been invaded by alien leguminous trees of the genusProsopis. We assessed the impact ofProsopisinvasion and clearing on vegetation cover in heavily grazed Nama-Karoo rangeland on two sheep farms in the Beaufort West district of the Western Cape province of South Africa. Our results suggest that, below critical threshold cover levels,Prosopistrees do not affect indigenous vegetation and add to overall rangeland vegetation cover. However, onceProsopiscover exceeds critical thresholds, the trees begin to negatively impact on indigenous vegetation (especially grasses) and overall vegetation cover. In addition, our data suggest that vegetation cover recovers afterProsopisclearing, being temporarily higher than pre-invasion levels possibly as a result of enhanced post-invasion soil fertility. Lastly, our results suggest thatProsopistrees reduce rangeland erosion potential at low cover and increase it after they exceed critical threshold cover. Information about thresholds ofProsopisimpact can be used to direct clearing efforts for maximum benefit when resources are limited. [ABSTRACT FROM PUBLISHER]

Eucalyptus camaldulensisDehnh. (red river gum; Myrtaceae) is an invasive tree in riparian habitats of the Western Cape, South Africa, where it replaces indigenous vegetation and affects ecosystem functioning. These invasions lead to changes in river geomorphology and reduction in stream flow. The mechanisms that drive these effects are poorly understood. The potential for allelopathic effects of aqueous extracts ofE. camaldulensistissues and of soil and litter collected beneathE. camaldulensistrees on the germination and seedling growth of four selected native plant species was investigated in a greenhouse experiment. Soils collected beneathE. camaldulensistrees were used in three treatments: untreated soils, sterilised soils and sterilised soils overlaid with a eucalypt litter layer. In addition, soils collected from underneath native species were used in two treatments: untreated soils and soils overlaid with a eucalypt litter layer. All soil treatments were watered with threeE. camaldulensisleaf, bark and root aqueous treatments. Compounds present in the aqueous extracts and fresh samples were identified using gas chromatography. Soil and aqueous treatments showed varying effects on germination and seedling growth of the four native species. Germination and seedling growth ofOlea europaeasubsp.africanaandDimorphotheca pluvialiswere significantly reduced byE. camaldulensisroot and bark aqueous extracts as well as by the soils treatments. The addition of eucalypt litter to native and sterilised soils reduced shoot and root growth of all four native species. Compounds such as -phellandrene, eucalyptol,p-menth-1-en-8-ol and -pinene, which have the potential to inhibit germination and plant growth, were identified inE. camaldulensisaqueous extracts and fresh samples. Although the methods applied in this study had limitations (e.g. lack of control treatment to litter addition), the results provide an additional motivation to prioritise removal of invasiveE. camaldulensisstands from riparian ecosystems. Restoration initiatives should target native species that are not negatively affected by allelopathy. [ABSTRACT FROM PUBLISHER]