Background: This paper reviewed the benefits and negative impacts of alien species that are currently listed in the Alien and Invasive Species Regulations of the National Environmental Management: Biodiversity Act (Act no 10 of 2004) and certain alien species that are not yet listed in the regulations for which conflicts of interest complicate management. Objectives: Specifically, it identified conflict-generating species, evaluated the causes and driving forces of these conflicts and assessed how the conflicts have affected management. Method: A simple scoring system was used to classify the alien species according to their relative degree of benefits and negative impacts. Conflict-generating species were then identified and further evaluated using an integrated cognitive hierarchy theory and risk perception framework to identify the value systems (intrinsic and economic) and risk perceptions associated with each conflict. Results: A total of 552 alien species were assessed. Most of the species were classified as inconsequential (55%) or destructive (29%). Beneficial (10%) and conflict-generating (6%) species made a minor contribution. The majority (46%) of the conflict cases were associated with more than one value system or both values and risk perception. The other conflicts cases were based on intrinsic (40%) and utilitarian (14%) value systems. Conclusions: Conflicts based on value and risk perceptions are inherently difficult to resolve because authorities need to balance the needs of different stakeholders while meeting the mandate of conserving the environment, ecosystem services and human well-being. This paper uses the identified conflict-generating species to highlight the challenges and trade-offs of managing invasive species in South Africa.

A major challenge for the management of biological invasions is to ensure that data and information from basic inventories and ecological research are used alongside data from the monitoring and evaluation of interventions to trigger and improve policy and management responses. To address this issue, South Africa has committed to report on the status of biological invasions and their management every 3 years. We propose a framework of indicators for reporting on biological invasions at a country level; assess the feasibility of the indicators using South Africa as a case study; and outline steps needed for indicator development. We argue that a national status report on biological invasions should explicitly consider indicators for pathways, species, and sites, and should report on interventions in terms of inputs, outputs, and outcomes. We propose 20 indicators based on data currently available, as well as existing international policy initiatives. For each indicator, we have developed a factsheet that includes different hierarchical metrics (considering data availability) and provide suggestions on assigning confidence levels. We also combine these indicators into four high‐level indicators to facilitate broader reporting and describe how forecasted indicators based on the concept of invasion debt could assist with scenario planning. We found that many of the data required for these indicators are already available in South Africa, but they have been poorly collated to date. However, data for the indicators of most direct value to policy and planning—those dealing with the impact of biological invasions and the outcome of interventions—are scarce. Policy implications. The framework of indicators developed here, for what we believe is the first ever national‐level report on the status of biological invasions and their management, will facilitate the inclusion of biological invasions in environmental reporting at national and international levels. By identifying knowledge gaps, a status report will also focus efforts on determining the size of a country's invasion debt and what can be done to reduce it.

South Africa has much to offer as a location for the study of biological invasions. It is an ecologically diverse country comprised of nine distinct terrestrial biomes, four recognised marine ecoregions, and two sub-Antarctic Islands. The country has a rich and chequered socio-political history, and a similarly varied history of species introductions. There has been a long tradition of large-scale conservation in the country, and efforts to manage and regulate invasions began in the nineteenth century, with some notable successes, but many setbacks. With the advent of democracy in the early 1990s, South Africa established large alien species control programmes to meet the dual demands of poverty alleviation and conservation, and has since pioneered regulatory approaches to address invasions. In terms of research, South Africa has played an important role in the development of invasion science globally. It continues to have one of the most active communities anywhere in the world, with strengths in theoretical and applied invasion science, and world-leading expertise in specific sub-disciplines (e.g. the classical biological control of invasive plants). In this introductory chapter to the book “Biological Invasions in South Africa”, we highlight key events that have affected biological invasions, their management, and the research conducted over the past two centuries. In so doing, we build on earlier reviews—from a national situational review of the state of knowledge in 1986, culminating most recently with a comprehensive report on the status of biological invasions and their management at a national level in 2018. Our book comprises 31 chapters (including this one), divided into seven parts that examine where we have come from, where we are, how we got here, why the issue is important, what we are doing about it, what we have learnt, and where we may be headed. The book lists over 1400 alien species that have established outside of captivity or cultivation. These species cost the country at least US$1 billion per year (~ZAR 15 billion), and threaten South Africa’s unique biodiversity. The introduction and spread of alien species, the impacts that they have had, the benefits that they have brought, and the attempts to manage them have provided many opportunities for research. Documenting what we have learned from this unplanned experiment is a primary goal of this book. We hope this book will allow readers to better understand biological invasions in South Africa, and thereby assist them in responding to the challenge of addressing the problem.

Seventy-seven alien freshwater species are currently naturalised in South Africa. This list includes 7 protozoan, 1 cnidarian, 2 cestode, 13 monogenean, 1 nematode, 1 oligochaete, 6 crustacean, 16 insect, 7 mollusc and 21 fish species. Their origins include all continents except Antarctica and the main pathways for their introduction into the wild are intentional releases (42% of taxa), as parasitic contaminants (35%) or stowaways (14%). Escape from captivity has been relatively unimportant (one fish and one crayfish) and direct introductions for fisheries (49% of taxa), biological control (19%) and stowaways or contaminants (22%) are the most common vectors. The chapter provides an overview of the alien freshwater taxa that are naturalised in South Africa and offers insights into which areas of research are data deficient. Generally, the introduction pathways and vectors for intentionally introduced taxa, such as insects imported for biological control or fishes introduced for fisheries, are well understood and documented. Data on other taxa, and particularly on invertebrates, are scant and only certain groups, such as the parasites of fishes, and snails, for which there is directed research interest, are documented. As a result, increased survey effort is urgently required.

Invasive alien species are a major driver of global change, impacting biodiversity, ecosystem services, and human livelihoods. To document these impacts, we present the Global Impacts Dataset of Invasive Alien Species (GIDIAS), a dataset on the positive, negative and neutral impacts of invasive alien species on nature, nature’s contributions to people, and good quality of life. This dataset arises from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services’ (IPBES) thematic assessment report of this topic. Data were compiled from published sources, including grey literature, reporting a direct observation of an invasive alien species’ impact. All impact records contain up to 52 fields of contextual information and attempt to link impacts to the global standard “environmental impact classification for alien taxa” (EICAT) and “socio-economic impact classification for alien taxa” (SEICAT). GIDIAS includes more than 22000 records of impacts caused by 3353 invasive alien species (plants, vertebrates, invertebrates, microorganisms) from all continents and realms (terrestrial, freshwater, marine), extracted from over 6700 sources. We intend GIDIAS to be a global resource for investigating and managing the variety of impacts of invasive alien species across taxa and regions.