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Africa's population is expected to triple by 2050, owing to rapid urbanisation and overall demographic trends. The combined pressures of urbanisation and climate change impact the ecosystem and the services it provides. As a result, additional dangers such as increased flooding, and environmental disruption have risen. Therefore, devising adaptive solutions to mitigate flood risk impacts while also building community resilience is needed. Evidence suggests that Nature‐based Solutions (NbS) can potentially alleviate floods and mitigate climate change impacts while also delivering other societal benefits. Despite rising NbS popularity following its recognition in the last decade, studies on its recognition in Africa remain limited. For this reason, this paper reviewed NbS studies conducted in East Africa (EA) to evaluate opportunities and barriers surrounding NbS adoption in EA. Academic literature published from January 2012 to May 2022 was reviewed using a comprehensive search of the SCOPUS database. Results show 14 papers have been published during the period, with the majority being post‐2020. In addition, the majority of the articles focused on cities and peri‐urban settlements, while public awareness, clear guidelines on performance monitoring, stakeholder inclusion, and diverse demonstration projects were highlighted as potential success factors for the adoption of NbS in EA. [ABSTRACT FROM AUTHOR]

Sao Paulo City, Brazil, a densely urbanized area in a tropical climate region, is facing increasing challenges from flooding. However, a promising solution has emerged in the form of Nature-Based Solutions (NBS) infrastructure, surpassing traditional grey technology in flood mitigation. This article examines the effectiveness of green roofs in reducing flood risks and highlights their superiority over conventional approaches. We analyzed the direct impacts of surface permeabilization in public areas (sidewalks, streets, and squares) and private areas (urban lots, subdivisions) on runoff volume and peak flow in the Aricanduva River basin in Sao Paulo city. We used a thoroughly validated hydrological model to compare the interference in the land use of the watershed between a green infrastructure type called Green Roof (GR) and a gray technology called Permeable Pavement (PP), in terms of hydrological efficiency in mitigating floods. The flow and water level simulations for varying areas with GR or PP covered a wide range, allowing for situations above or below the canal overflow level, which provided a good distinction of the impact of boundary conditions. Overall, we observed a positive hydrological response, with a reduction in peak flow and runoff volume proportional to the increase in permeable area, and consequently, proportional to the increase in GR or PP surface within the contributing area. As the main contribution, the hydrological performance calculated with the variation of GR was remarkably superior to the variation of PP in terms of requiring a smaller coverage area with interference to prevent overflow or achieve equivalent efficiency. It is worth noting that the substitution of approximately 24% of the gray roof area with GR prevented canal overflow, which is notably lower than the required substitution of approximately 40% for PP interference. We reinforce the relevance of green roofs as an option to mitigate intense hydrological effects in urban areas and, more importantly, paves the way for other NBS with the same hydrological principles and environmental co-benefits to work individually or in combination. [ABSTRACT FROM AUTHOR]

For the last 30 years, interest has focused on biochar and its potential to store carbon in soil to mitigate climate change whilst improving soil properties for increased crop production and, therefore, could play a critical role in both agricultural sustainability and broader environmental aims. Biochar, a carbonaceous product, is formed from organic feedstock pyrolysised in the absence of air and, therefore, is a potential means of recycling organic waste. However, different feedstock and pyrolysis conditions result in a biochar with a range of altered characteristics. These characteristics influence nitrogen transformation processes in soil and result in the metabolism of different substrates and the formation of different products, which have different effects on agricultural yield. This paper reviews how the production of biochar, from varying feedstock and pyrolysis conditions, results in different biochar characteristics that influence each stage of the nitrogen cycle, namely processes involved in fixation, assimilation, mineralisation and denitrification. The nitrogen cycle is briefly outlined, providing a structure for the following discussion on influential biochar characteristics including carbon composition (whether recalcitrant or rapidly metabolisable), mineral composition, surface area, porosity, cation exchange capacity, inhibitory substances and pH and so on. Hence, after the addition of biochar to soil, microbial biomass and diversity, soil porosity, bulk density, water-holding capacity, cation exchange capacity, pH and other parameters change, but that change is subject to the type and amount of biochar. Hence, products from soil-based nitrogen transformation processes, which may be beneficial for plant growth, are highly dependent on biochar characteristics. The paper concludes with a diagrammatic summation of the influence of biochar on each phase of the nitrogen cycle, which, it is hoped, will serve as a reference for both students and biochar practitioners. [ABSTRACT FROM AUTHOR]