Southern African cities face several challenges including management of rapid urbanization, rising populations, expanding informal settlements; adequate water and other service provision, and a host of governance challenges. Climate change and variability add a compounding effect to this complex, multi stressor context. Addressing the complexity requires an understanding of urban ecosystems functioning and interactions amongst the built and natural environment (climate) and human systems. In this paper we argue that learning is essential for cities to be resilient to current and future challenges. We profile the Future Resilience for African CiTies And Lands (FRACTAL) project which contributed towards climate resilient development by providing relevant climate information for decision-making at the city regional scale in southern Africa. Following FRACTAL’s city-to-city learning approach of sharing good practices, knowledge and experiences framed around transdisciplinary research, the study cities of Harare, Lusaka, Windhoek and Durban conducted city learning exchange visits between 2017 and 2018. We used a mixed methods approach to collect and analyze historical climate and hydrological data and current socio-economic and development data among the cities. A qualitative, in-depth, case study comparative analysis was used to identify similarities and differences as well as lessons drawn from the learning process during the city exchanges and these were complimented by desktop studies. Results showed water scarcity, large informal settlements, reliance on external water and energy sources, inadequate protection of ecologically sensitive resources and service provision as some of the common complications in the cities. Several lessons and transferable practices learnt from the cities included effective water conservation and waste management and the use of public-private partnerships in Windhoek, community engagements in Durban and Lusaka while lessons on decisive leadership in dealing with informal settlements emanated from Harare’s limited informal settlements. Lastly, Durban’s Adaptation Charter and integrated climate planning provided lessons for biodiversity protection and mainstreaming climate change at city governance level. While we recognize that cities are context-specific we consider these good practices as being broadly transferable to other southern African cities. We conclude that social, experiential and structured learning can be an innovative way of multi-stakeholder engagement and a useful approach to increase city resilience planning across southern Africa and cities that face similar developmental challenges.

This paper provides a synthesis of current knowledge on phytoplankton production, seasonality, and stratification in tropical African lakes and considers the effects of nutrient enrichment and the potential impacts of climate warming on phytoplankton production and composition. Tropical African lakes are especially sensitive to climate warming as they experience wide fluctuations in the thermocline over a narrow range of high water temperatures. Recent climate warming has reduced phytoplankton biomass and production in the lakes. A decline in the production of palatable chlorophytes and an increase in cyanobacteria has led to reduced zooplankton production and a consequent decline in fish stocks, all of which can be associated with the elevated water temperatures. This indicates that even moderate climate warming may destabilise phytoplankton dynamics in tropical African lakes, thereby reducing water quality and food resources for planktivorous fish, with consequent negative impacts on human livelihoods.

The influence of climatic variables (rainfall, temperature and evaporation rates) and lake water levels on the stocks of the sardine fish species Limnothrissa miodon (Boulenger), commonly known as Kapenta in Lake Kariba, was investigated. Secondary data of the climatic variables, water levels and fish catches recorded from 1963 to 2008 were analysed to determine their trends over time as well as the relationships among them. The analyses showed that rainfall is decreasing at a rate of 0.63 mm per year around Lake Kariba, while evaporation rates have increased by 31% at an average rate of 2.77 mm per year since 1963. The temperatures around the Kariba area have been rising since 1964; with the maximum range increasing at a faster rate than the minimum temperatures. Kapenta fish production has decreased significantly (R ² =0.85, P≤0.05) since 1974 at an average rate of 24.19 metric tons per year. This pattern of decrease was also observed in the artisanal fish catches that have declined at an average rate of 37.26 metric tons per year between 1974 and 2003. All the climatic factors as well as the water levels could explain variations in the Kapenta fish catches with the water levels exerting the greatest influence (R ² =0.84, P 0.05); followed by maximum temperature (R ² = 0.72, P≤0.05), evaporation and rainfall. In turn, water levels are largely influenced by climate with temperature and rainfall explaining a significant portion of the variation in the water levels (R ² =0.99, and R ² =0.93, P≤0.05) in that order. This suggests that both climate (maximum temperature in particular) and nutrients, which are influenced by water levels, are the primary determinants of Lake Kariba's Kapenta production. Concerning are the possibilities that a changing climate in and around the lake may continue to adversely affect water levels, the stratification cycle, nutrient fluxes and the Kapenta fish production in the lake.

In recent decades, the aquaculture industry has seen exponential growth worldwide, surpassing other food production sectors. This review aims to explore the dynamics of aqua feed production, particularly the shift from conventional to local feed production in Africa, driven by cost-effectiveness and the availability of raw materials. This review examines various scientific publications on aqua feed, focusing on both conventional and novel feed formulations and their impact on both small-scale and large-scale aquaculture. Commonly used aqua feed ingredients among African farmers include cassava, maize gluten, groundnut oilcake, sunflower oilcake, soybean meal, kale, peas, garlic, shrimp wastes, and waste blood. Novel ingredients such as insect-based diets, micro-algae, and fish discard formulations are also explored. Aqua feed composition impacts aqua waste, water quality, algae, oxygen demand, fish mortality, and eutrophication, and findings from literature reiterate the need to reorient feed formulation methods and ingredients to achieve a circular economy in Africa. This will entail promoting increased fish production at minimal costs and creating employment while supporting climate adaptation and mitigation efforts. Ultimately, the aqua feed sector has the potential to grow sustainably through the adoption of feed alternatives that prioritize sustainable production and encourage beneficiation studies.