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The global uptake of green infrastructure in urban settings holds considerable promise for fostering both social and ecological benefits. Recognizing the imperative to ensure equitable distribution of these advantages, this paper draws on the rich traditions of justice considerations within urban studies to inform research on urban greening. Focusing on three key trends - reconceptualizing the 'urban' category, acknowledging the role of historical processes in shaping contemporary uneven and unjust geographies, and considering power dynamics in infrastructure development - we propose five tenets for advancing justice-focused urban greening research. These tenets encourage researchers to act as knowledge brokers, practice reflexivity, recognise the complex dimensions of justice which diversity of scale might reveal, embrace uncertainty, and cultivate a "modest imaginary" concerning infrastructure projects. [ABSTRACT FROM AUTHOR]

• CityLabs experiment with knowledge co-production between government and academia. • Developing transdisciplinary spaces requires deliberate formulation and flexibility. • Experimentation and effective co-production require trust and mutual understanding. • Learning through experimentation in 'living' cities is iterative and unpredictable. Applied research has evolved to play an important role in understanding and reorienting relationships between different knowledge partnerships in urban sustainability. This paper reflects on experiences from the global South on knowledge co-production experiments through 'CityLabs', which are forums for bringing together different knowledge brokers (particularly government and academia) to co-produce policy-relevant urban knowledge. Each CityLab experimented with different configurations to generate knowledge relevant for addressing urban sustainability challenges. This paper reflects on these experiences and identifies emerging common principles. These include: deliberate formulation of safe spaces, in which to engage, willingness for flexibility around the direction, focus and outputs, and carefully fostering trust and mutual understanding among participants. Urban experimentation, and CityLabs in particular, provide real opportunities for facilitating learning, reframing issues and shifting practices around urban sustainability between government and the academy. [ABSTRACT FROM AUTHOR]

Globally, as trends of urbanisation continue to intensify, there has been increasing concern over the impacts of urban expansion on biodiversity and greater attention towards addressing these impacts. Ecological infrastructure such as urban rivers and their catchments may enhance biodiversity, ecological functioning and ecosystem service delivery within cities. Birds are good indicators of urban habitat quality because their ecology is well-studied and they are habitat selective. This study assesses the ecological value of a small urban river catchment in Cape Town, South Africa, in terms of its effect on the taxonomic and functional diversity of birds. 178 bird counts were carried out at 89 sites and 95 species were recorded. The nine functional groups considered were present in equal proportions in the catchment and in the whole of southern Africa, making the catchment a microcosm of the region’s avifauna in terms of functional composition. Using RLQ and fourth-corner analyses, we showed that the river was responsible for the occurrence of certain species and functional groups that would not otherwise occur in the suburbs. Nutrient movers, insectivores, scavengers and seed dispersers responded strongly to a gradient of distance from the river and the position on the river. Contrary to the homogenised assemblage that might be expected of an urban area, the catchment contains a taxonomically and functionally diverse bird assemblage. The combination of a river, a heterogeneous urban matrix and an adjacent national park makes this catchment an exemplar of the value of ecological infrastructure for urban biodiversity. [ABSTRACT FROM AUTHOR]

• Human-mediated flows of nitrogen dominate natural flows in an urban watershed in South Africa. • A large urban wetland system plays a crucial role in mitigating nitrogen cascades in the coastal zone. • A large urban wetland system provides an important, yet under appreciated, ecosystem service to the City. • Substantial research gaps exist in understanding nitrogen budgets of African cities. Urban watersheds receive excessively high Nitrogen (N) loads predominantly via N deposition, fertilizer use, stormwater runoff, treated effluent discharge and sewage leaks. Beyond engineered solutions, the capacity of these systems to remove this excess N is largely dependent upon the functioning of riparian and wetland ecosystems, which in urban areas are highly modified, fragmented and increasingly under pressure. Appropriate management of urban watersheds needs to consider N flux and process rates that occur within the urban landscape. This research provides a preliminary quantification of the relative magnitudes of N flux in the context of a small urban watershed comprising key features of cities in the Global South: a mosaic of informal and formal residential, peri-urban agriculture and stressed service delivery. For a watershed system of 88 km2, total N inputs amount to 2.82 Gg N yr−1, 78 % of which is in the form of household food. N outputs amount to 2.35 Gg N yr−1 with 86 % of that coming out of wastewater streams either as treated effluent or during the denitrification process. An estimated 0.17 Gg N yr−1 accumulates in the system as plant biomass, in groundwater, soils and landfill. The Zeekoevlei wetland system is hypothesised to remove 76 % of total N which drains off the urban landscape, indicating an important service provided to the City, in addition to other well documented ecosystem services. In this urban system, our estimates indicate N flux rates almost 3 times higher than what would be here naturally in a nutrient-deplete Fynbos system. This work daylights important monitoring and research needs in order to better understand the role of the urban landscape and wetland ecosystems in a highly human-mediated N cycle. [ABSTRACT FROM AUTHOR]

Historic land use practices have dramatically altered landscapes across all scales, homogenising them and restricting opportunities for humans and wildlife. The need for multifunctional landscapes which simultaneously provide food security, livelihood opportunities, maintenance of species and ecological functions, and fulfil cultural, aesthetic recreational needs is now recognised. Numerous theoretical and technical tools have been developed to understand different landscape elements, in particular the emerging research area of ecosystem services. A brief review of these tools not only shows considerable growth and opportunity, but also serves to highlight a lack of research integration and a lag in implementation. The effective implementation of sustainable multifunctional landscapes requires true transdisciplinary engagement. We suggest the use of learning organisations to bring together the multiple stakeholders necessary for multifunctional landscapes to take purchase. [Copyright &y& Elsevier]

• A rural-urban gradient in Cape Town shows a decline in plant diversity. • In the city plant communities vary across a racial and socio-economic gradient. • Plant species and trait richness are less in poorer neighbourhoods. • Links between plant diversity and resilience suggest how environmental injustice persists. In this study we explore species richness and traits across two urban gradients in the City of Cape Town. The first is the natural-urban boundary and the second is a socio-economic gradient informed by historical race-based apartheid planning. Plant species and cover were recorded in 156 plots sampled from conservation areas, private gardens, and public open green space. The socio-economic gradient transitioned from wealthier, predominantly white neighbourhoods to poorer, predominantly black neighbourhoods. The socio-economic gradient was selected to fall within one original vegetation type to ensure a consistent biophysical template. There is a marked shift between the natural and urban plant communities in the City of Cape Town, with little structural affinity. Urban landscapes are dominated by grass, with low diversity compared to natural counterparts. A significant ecological gradient of reduced biodiversity, traits, and in turn functionality, was found across the socio-economic gradient. Wealthier communities benefit from more private green space, more public green space, and a greater plant diversity. Poorer communities have limited green space on all fronts, and lower plant and trait diversity. Plant communities with limited diversity are less resilient and if exposed to environmental perturbation would lose species, and associated ecosystem services faster than a species rich community. These species-poor plant communities mirror historical apartheid planning that is resistant to change. Based on how biodiversity, functionality, and associated ecosystem services and ecosystem stability are linked, the results of this study suggests how significant environmental injustice persists in the City of Cape Town. [ABSTRACT FROM AUTHOR]