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The three most abundant stable isotopes of Silicon (Si), 28Si, 29Si, and 30Si, all occur in plants. Isotope studies are a potential tool to explore uptake and function of plant Si, and it is a developing field. However, there is a lack of studies from natural environments, and species from the African continent, and all plant parts including reproductive structures. In this study, naturally grown papyrus plants were sampled from the Okavango Delta and divided into five organs, i.e. umbel, culm, scales, rhizome, and roots. Samples were analysed for TN, TOC, BSi, TP concentrations, and for Si isotopes. Each organ of papyrus is represented by two samples, one from juvenile tissue and one mature (apart from the roots where age is difficult to determine). The study confirms that papyrus is a high Si-accumulating species, with BSi ranging from 0.88 % in rhizomes to 6.61 % in roots. High Si precipitation in the roots leads to an enrichment in heavy Si isotopes in the residual mobile Si pool, as light Si isotopes precipitate in phytoliths in the roots, even though in this study phytoliths were identified for all organs except for roots. In papyrus, shoot organs gradually become enriched in heavy Si isotopes along the transpiration stream, with an increase in heavy isotopes from rhizomes to scales, culm, and umbel, same pattern that has been observed for other plants in literature.

1. Humanity is on a deeply unsustainable trajectory. We are exceeding planetary boundaries and unlikely to meet many international sustainable development goals and global environmental targets. Until recently, there was no broadly accepted framework of interventions that could ignite the transformations needed to achieve these desired targets and goals. 2. As a component of the IPBES Global Assessment, we conducted an iterative expert deliberation process with an extensive review of scenarios and pathways to sustainability, including the broader literature on indirect drivers, social change and sustainability transformation. We asked, what are the most important elements of pathways to sustainability? 3. Applying a social-ecological systems lens, we identified eight priority points for intervention (leverage points) and five overarching strategic actions and priority interventions (levers), which appear to be key to societal transformation. The eight leverage points are: (1) Visions of a good life, (2) Total consumption and waste, (3) Latent values of responsibility, (4) Inequalities, (5) Justice and inclusion in conservation, (6) Externalities from trade and other telecouplings, (7) Responsible technology, innovation and investment, and (8) Education and knowledge generation and sharing. The five intertwined levers can be applied across the eight leverage points and more broadly. These include: (A) Incentives and capacity building, (B) Coordination across sectors and jurisdictions, (C) Pre-emptive action, (D) Adaptive decision-making and (E) Environmental law and implementation. The levers and leverage points are all non-substitutable, and each enables others, likely leading to synergistic benefits. 4. Transformative change towards sustainable pathways requires more than a simple scaling-up of sustainability initiatives-it entails addressing these levers and leverage points to change the fabric of legal, political, economic and other social systems. These levers a

We present one year of continuous monitoring of methane emissions at two contrasting sites in the Okavango Delta, a UNESCO World Heritage site located in North-Western Botswana. The wetlands of the Okavango Delta are in pristine condition and can be separated into three categories: permanently flooded, seasonally flooded (3-6 months per year) and occasionally flooded (typically once per decade). We set up two eddy-covariance systems in August 2017, one at Guma Lagoon (18°57'53.01" S; 22°22'16.20" E) at the edge of an extensive papyrus bed in the permanently-flooded section of the delta, and the second one at Nxaraga on the SW edge of Chief’s Island (19°32'53'' S; 23°10'45'' E) in the seasonal floodplain. We also conduct monthly measurements of methane and carbon dioxide fluxes by using a clear dynamic chamber at Nxaraga along transects chosen to span the natural soil moisture gradient (very dry to waterlogged soils). We observed contrasting spatial and temporal patterns of methane emissions between the sites as well as significant differences in emission intensities. Methane hotspots were observed in the Guma Lagoon papyrus swamp whereas fluxes at Nxaraga increased gradually with distance into the floodplain, which correlates with the spatial gradient of soil moisture in the seasonal floodplain. The differences observed at the two measurement sites suggest different controls, with soil moisture likely to be the dominant one at the seasonal floodplain. In contrast, we expect the emissions from the permanent wetland to be driven by a complex set of mechanisms, which could include plant-mediated transport, diffusion at the water-air interface, bubbling and convective flow within the water column.