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  Carbon storage in soils

  Soils are a pivotal component in the global carbon cycle, while carbon storage in soils is a natural phenomenon involving organic carbon. Maintaining or increasing soil carbon levels is beneficial for many ecosystem services. Soil carbon is also a soil condition indicator and a key focus of several Sustainable Development Goals. This chapter describes the forms of carbon in soils, the quantification of carbon stocks and storage, the processes underlying the heterogeneous distribution of carbon stocks across the planet and their dynamics, land-use changes and practices that affect soil carbon stocks, as well as the socioeconomic benefits of soil carbon storage.
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  Global option space for organic agriculture is delimited by nitrogen availability

  Organic agriculture is widely accepted as a strategy to reduce the environmental impacts of food production and help achieve global climate and biodiversity targets. However, studies concluding that organic farming could satisfy global food demand have overlooked the key role that nitrogen plays in sustaining crop yields. Using a spatially explicit biophysical optimization model that accounts for crop growth nitrogen requirements, we show that, in the absence of synthetic nitrogen fertilizers, the production gap between organic and conventional agriculture increases as organic agriculture expands globally (with organic producing 36% less food for human consumption than conventional in a fully organic world). Yet, by targeting both food supply (via a redesign of the livestock sector) and demand (by reducing average per capita caloric intake), public policies could support a transition towards organic agriculture in 40–60% of the global agricultural area even under current nitrogen limitations thus helping to achieve important environmental and health benefits.
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  Priority science can accelerate agroforestry as a natural climate solution

  The expansion of agroforestry could provide substantial climate change mitigation (up to 0.31 Pg C yr−1), comparable to other prominent natural climate solutions such as reforestation. Yet, climate-focused agroforestry efforts grapple with ambiguity about which agroforestry actions provide mitigation, uncertainty about the magnitude of that mitigation and inability to reliably track progress. In this Perspective, we define agroforestry as a natural climate solution, discuss current understanding of the controls on farm-scale mitigation potential and highlight recent innovation on emergent, high-resolution remote sensing methods to enable detection, measurement and monitoring. We also assess the status of agroforestry in the context of global climate ambitions, highlighting regions of underappreciated expansion opportunity and identifying priorities for policy and praxis.
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  Regenerative Agriculture: An agronomic perspective

  Agriculture is in crisis. Soil health is collapsing. Biodiversity faces the sixth mass extinction. Crop yields are plateauing. Against this crisis narrative swells a clarion call for Regenerative Agriculture. But what is Regenerative Agriculture, and why is it gaining such prominence? Which problems does it solve, and how? Here we address these questions from an agronomic perspective. The term Regenerative Agriculture has actually been in use for some time, but there has been a resurgence of interest over the past 5 years. It is supported from what are often considered opposite poles of the debate on agriculture and food. Regenerative Agriculture has been promoted strongly by civil society and NGOs as well as by many of the major multi-national food companies. Many practices promoted as regenerative, including crop residue retention, cover cropping and reduced tillage are central to the canon of ‘good agricultural practices’, while others are contested and at best niche (e.g. permaculture, holistic grazing). Worryingly, these practices are generally promoted with little regard to context. Practices most often encouraged (such as no tillage, no pesticides or no external nutrient inputs) are unlikely to lead to the benefits claimed in all places. We argue that the resurgence of interest in Regenerative Agriculture represents a re-framing of what have been considered to be two contrasting approaches to agricultural futures, namely agroecology and sustainable intensification, under the same banner. This is more likely to confuse than to clarify the public debate. More importantly, it draws attention away from more fundamental challenges. We conclude by providing guidance for research agronomists who want to engage with Regenerative Agriculture.