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The Water-Energy-Food Nexus approach to the governance of natural resources seeks to identify and address the synergies and trade-offs amongst traditionally separated sectors, to capture significant feedbacks that have so far remained insufficiently understood and regulated. One key specificity of the Nexus approach is the need for intersectoral, cross-scale and stakeholder integration, which is particularly challenging due to the lack of policy coordination prevailing in many countries. Yet, some emerging integrated policy processes, such as those aimed at implementing nationally determined contributions (NDCs) under the 2015 Paris Agreement, may offer a sufficient level of integration to mainstream the Nexus approach. This article focuses on the potential of such NDC processes in Brazil. NDC processes in China, the European Union, India and Mexico are used as indicators associated with higher or lower degrees of integration for a more specific analysis of the case of Brazil. The article concludes that the barriers to sectoral integration raised by the dominant position of the agricultural sector in Brazil as regards, among other things, environmental legislation, are unlikely to be overcome by internal action. This represents a threat to achieving the target of zero deforestation in Brazil, considering the cropland-livestock forestry feedbacks involved in the growing demand for agricultural commodities from China. NDCs already provide space for international cooperation, which could be further developed to include measures for linking demand for agricultural commodities from the EU and China, and massive land-use change and deforestation in Brazil. Key policy insights The NDCs from India, China, EU, Mexico and Brazil recognize, to varying extents, the Nexus approach in their climate policies, particularly the link with water uses in agriculture. The NDCs from EU, Mexico and Brazil include some elaborated Nexus issues related to indirect land use-forestry-agriculture. Sectoral integration could be progressively strengthened under the Nexus approach as part of the five-yearly updates of the NDCs. The NDCs from Brazil and China could provide a policy window to integrate indirect land use-forestry-agriculture collaborative measures, for the purposes of tackling the deforestation trade-off resulting from Brazilian exports of soybeans to China. [ABSTRACT FROM AUTHOR]

Enhanced silicate rock weathering (ERW), deployable with croplands, has potential use for atmospheric carbon dioxide (CO 2 ) removal (CDR), which is now necessary to mitigate anthropogenic climate change 1 . ERW also has possible co-benefits for improved food and soil security, and reduced ocean acidification 2-4 . Here we use an integrated performance modelling approach to make an initial techno-economic assessment for 2050, quantifying how CDR potential and costs vary among nations in relation to business-as-usual energy policies and policies consistent with limiting future warming to 2 degrees Celsius 5 . China, India, the USA and Brazil have great potential to help achieve average global CDR goals of 0.5 to 2 gigatonnes of carbon dioxide (CO 2 ) per year with extraction costs of approximately US$80-180 per tonne of CO 2 . These goals and costs are robust, regardless of future energy policies. Deployment within existing croplands offers opportunities to align agriculture and climate policy. However, success will depend upon overcoming political and social inertia to develop regulatory and incentive frameworks. We discuss the challenges and opportunities of ERW deployment, including the potential for excess industrial silicate materials (basalt mine overburden, concrete, and iron and steel slag) to obviate the need for new mining, as well as uncertainties in soil weathering rates and land-ocean transfer of weathered products.