An ecological metaphor can enable transitions towards regenerative circular economies. Yet, this potential remains latent because its conceptual development, which is a prerequisite for its practical operationalization, is in its incipient phase and largely vague. To strengthen its epistemological underpinning, we propose a forward-looking interdisciplinary research agenda which brings together theories, ontological positions, analytical approaches, and strategies of action from ecological economics, panarchy theory, socio-metabolic research, process ecology, environ network theory, the constructal law, nature-based solutions, complexity economics, doughnut economics, regenerative economics, and ergodicity economics. The agenda facilitates the concentration, consolidation, and acceleration of theoretical and methodological innovation for the generation and accumulation of a diverse yet coherent body of knowledge on the interpretation of the process of regeneration and for illuminating the ways in which regenerative circular economies may function.

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Considering the importance of waste metals for the transition to circular economies, this study follows a bio-inspired approach to evaluate their material and monetary global trade patterns for sustainability and equity. Between 2000 and 2022, the global trade grew by 5 % in trading countries, by 37 % in trade links, by 71 % in material flows, and by 569 % in economic flows. Driven by indirect effects, the average circulation of material and monetary flows ranged between 21.8–34.9 % depending on the demand or supply perspective but showed a declining trend. Due to homogenization, high network redundancy, and low network efficiency the trade remained robust yet outside the "window of vitality" characterizing natural ecosystems. A few, mostly high-income countries dominated the market, consolidating imports of high-value metal waste mostly from low- and middle-income exporters. Policies should address circularity and trade inequities, accounting for environmental and social ramifications throughout the lifecycle of products and materials.@en

The Fourth Assessment Report of IPCC reports that greenhouse gas emissions can be reduced by about 30-50% in 2030 at costs below 100 US$/tCO₂ based on an assessment of both bottom-up and top-down studies. Here, we have looked in more detail into the outcomes of specific models and also analyzed the economic potentials at the sectoral and regional level. At the aggregated level, the findings of the IPCC report are confirmed. However, substantial differences are found at the sectoral level. At the same time, there seems to be no systematic difference in the reduction potential reported by top-down and bottom-up approaches. The largest reduction potential as a response to carbon prices exists in the energy supply sector. Reduction potential in the building sector may carry relatively low costs. Although uncertainties are considerable, the modeling results and the bottom-up analyses all suggest that at the global level around 50% of greenhouse gas emissions may be reduced at carbon price (costs) below 100$/tCO₂-eq-but with a wide range of 30-60%. At a carbon price (costs) less than 20$/tCO₂-eq, still 10-35% of emissions may be abated. The variation of results is higher at low carbon-price levels than at high levels.

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