Jana Fried

Ornamental gardening has historically been, and continues to be, a primary pathway for plant introductions into southern Africa. Knowing which alien plants are being sold and used as ornamentals in the subregion is important to assess the potential for future biological invasions and conflicts between stakeholders. We compiled a list of all plant taxa on sale across eleven nurseries in Botswana (3), Namibia (2) and Zimbabwe (6) by accessing the plants in stock either on the nurseries’ websites, on social media or via stock lists shared by the nursery owners. The compilation was matched with the Global Register of Introduced and Invasive Species to identify invasive taxa. Of 1 193 species that were found to be on sale, 784 are alien to the continental Southern African Development Community (SADC) subregion, 289 have established alien populations in at least one continental SADC country, and 82 are considered invasive in at least one continental SADC country. Many of the established and invasive plants are popular trees and shrubs in the subregion and worldwide. Most of them have a wide native range usually covering more than one continent. This paper provides a quantification of invasion debt due to the ornamental sector in southern Africa and a baseline to identify priorities for risk analysis and potential regulation or control at a subregional level.

Southern Africa has a well-documented history of intentional plant introductions for ornamental purposes, but some of these plants have become widespread damaging invaders. Conflicts can arise when stakeholders’ attitudes differ towards ornamental invasive plants and their management. We examined the views of stakeholders involved in the ornamental sector and environmental management across Southern Africa in light of the strategic actions proposed by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services' thematic assessment on ‘Invasive Alien Species and their Control.’ Our analysis is based on semi-structured interviews, informal conversations, and observations with 78 environmental specialists, 30 ornamental-related industry staff, and 24 plant enthusiasts from Botswana, Namibia, Zimbabwe, South Africa, Zambia, Democratic Republic of Congo, and Eswatini. Our analysis shows that significant efforts are ongoing in Southern Africa to address biological invasions from the ornamental sector. However, they need more integration and consideration of the broader geopolitical and socio-historical context. We reflected on these needs and recommend: 1) improving cohesion and collaboration amongst stakeholders, 2) ensuring pluralism by recognising and valuing marginalised groups, 3) addressing power differences and superiority-inferiority complexes, and 4) seeking alliances with existing sub-regional groups working in the realm of nature-society interplay. We believe that our recommendations contribute toward the necessary transformative change for tackling the underlying political and economic causes of plant invasions derived from the ornamental sector in the sub-region.

Background: Ornamental gardening is one of the main historical and current pathways for plant introductions into southern Africa. A few introduced ornamental plants have become invasive, sometimes triggering conflicts between stakeholders. Knowing which alien plants are being sold and used as ornamentals in the sub-region is important to assess the potential for future biological invasions and conflicts between stakeholders. Objectives: This paper identifies and characterises the ornamental plants on sale in three southern African countries, and compared these to lists of plants considered invasive in the area of the continental Southern African Development Community (SADC). Methods: We compiled all plant taxa sold across eleven nurseries in Botswana (3), Namibia (2) and Zimbabwe (6) by accessing the plants in stock either on the nurseries’ website, on social media, and via stock lists shared by the nursery owners. The compilation was matched with the Global Register of Introduced and Invasive Species to identify invasive taxa. This sub-group was characterised by growth form and biogeographical origin. Results: 1,193 species were found to be sold, of which 784 are alien to the continental SADC sub-region, 289 have established alien populations in at least one continental SADC country, and 82 are considered invasive in at least one continental SADC country. Many of the established and invasive plants are popular trees and shrubs in the sub-region and worldwide. Most of them have a wide native range usually covering more than one continent. Conclusions: This paper provides a quantification of the invasion debt due to the ornamental sector in southern Africa, and a baseline to identify priorities for risk analysis and potential regulation or control at a sub-regional level. Approaches to reduce the sale of invasive species, however, need to be considered carefully, since their current popularity across the sub-region could make them a source of conflict between the ornamental horticulture sector and those tasked with managing biological invasions.

Sub-Saharan Africa (SSA) is increasingly experiencing unprecedented drought-to-flood events, posing critical challenges to water and food security. These rapid or seasonal transitions between extreme hydroclimatic conditions underline the urgency of advancing climate adaptation strategies and enhancing risk management frameworks in the region. However, the role of large-scale climate variability, such as the El Niño-Southern Oscillation (ENSO), Atlantic Multidecadal Variability (AMV), and Indian Ocean Dipole (IOD), in influencing decadal trends in these events across SSA remains inadequately understood.This study aims to address this gap by evaluating how well eight single-model initial-condition large ensembles (SMILEs) from the sixth phase of the Coupled Model Intercomparison Project (CMIP6) simulate the spatiotemporal patterns of drought-to-flood events in SSA. ERA5-Land data is used as the observational reference. We also investigate potential seasonal links between the probability of drought-to-flood events and large-scale modes of climate variability.Drought-to-flood events are defined as the sequential occurrence of a flood following a drought. To capture these events, we employ a variable threshold approach for identifying droughts, while floods are characterized using absolute thresholds (50th to 90th percentiles). To assess potential differences between meteorological and hydrological definitions of drought and flood, we compare results derived from precipitation, soil moisture, and runoff datasets.

Humans and ornamental plants have a long relationship that could explain why ornamental gardening has been one of the main reasons for intentionally introducing and spreading plants worldwide. In Southern Africa, a significant part of the alien flora was introduced for ornamental purposes. Some species have become invasive, with ecological and socio‐economic impacts that can create conflicts between stakeholders, depending on their relationships with the species. This paper unpacks how the ornamental industry in Southern Africa operates as well as people's preferences for ornamental plants and practices to highlight links between the industry and plant invasions and to help address potential conflicts. Drawing on empirical data primarily collected in 2022/23 in Botswana, Namibia and Zimbabwe (and other Southern African countries), our results show that Southern Africa's ornamental industry is highly influenced by the global industry, especially South Africa. The sector provides ‘formal’ and ‘informal’ jobs to people in urban areas, especially middle‐aged women from ethnic majorities. The sector's operation and gardening practices show expressions of the typical cultural hybridity of postcolonial states where hegemonic and subaltern practices coexist and mix. Alien plants and foreign styles often symbolise higher social status, but controversially, socially privileged groups are publicly leading shifts towards more geographically contextualised practices and native plants. We conclude by arguing that recognising the influences that historical processes have on the sector's operation and its links with alien plants is essential for a more ethically sound and fair stakeholder engagement in preventing and managing plant invasions from the ornamental industry in Southern Africa.

Global urbanisation is leading to the degradation of living soils, with substantial and direct impacts on climate, biodiversity, food security, and human health. Urban land use policies are beginning to address soil protection. However, they rarely address the depollution and remediation of urban soils and the revitalisation of the agricultural socio-economic fabric, both essential to recover and maintain healthy soils. Instead polluted soils are often managed through further soil sealing (i.e. covering with a plastic ‘geotextile’ layer to isolate it and adding new soil on top). As alternatives, emerging urban communities of practice are currently experimenting with integrated and holistic practices of soil care, such as sourcing urban organic waste streams (food waste, leaves, grass clippings, waste from breweries, ecological paperboard packaging, etc.) for topsoil regeneration or using nature-based approaches (e.g. bioremediation) for the depollution of topsoils. Such practices urgently need enabling and adequate policy frameworks to be mainstreamed and aligned with related policies regarding climate action, green/blue infrastructure and urban food policy plans.

Many species have been intentionally introduced to new regions for their benefits. Some of these alien species cause damage, others do not (or at least have not yet). There are several approaches to address this problem: prohibit taxa that will cause damage, try to limit damages while preserving benefits, or promote taxa that are safe. In the present article, we unpack the safe list approach, which we define as “a list of taxa alien to the region of interest that are considered of sufficiently low risk of invasion and impact that the taxa can be widely used without concerns of negative impacts.” We discuss the potential use of safe lists in the management of biological invasions; disentangle aspects related to the purpose, development, implementation, and impact of safe lists; and provide guidance for those considering to develop and implement such lists.

Urban living laboratories: Opportunities for modelling sustainability transitions: Here, a group of academics present Urban Living Laboratories to study sustainable food production systems, using systems dynamic modelling to analyse policy alternatives. Urban Living Laboratories (ULLs) have shown first promising signs of being valuable platforms for understanding transition phenomena. To address our time’s diverse grand societal challenges (like climate change and biodiversity loss), we must transition to truly sustainable systems, possibly the most significant shift facing modern civilisations. Such transitions involve coupled technological, social, economic and environmental shifts and demand transformative approaches with new forms of organisation and management.