Publications

<p>This document is the Annex of the report on the innovative market and policy instruments to promote the agro-ecological transition strategies (<a href="https://doi.org/10.5281/zenodo.5578065">Galioto et al. 2021</a>) which includes a more detailed description of all the 15 case studies.</p>

[EN] The global soil carbon pool comprises soil organic carbon (SOC), found in almost all soils, and soil inorganic carbon (SIC), in calcareous soils. Despite their agricultural significance, calcareous soils, which exhibit diverse chemical properties and are found in varied environments, have historically been understudied. Using soils obtained from a decade-long, fully factorial field experiment located on temperate, near neutral pH, calcareous soils, this study examined the influence of cover crops (no-cover vs radish) and three levels of tillage intensity: shallow (10¿cm) and deep (20¿cm) non-inversion, and plough (25¿cm inversion) on SOC and SIC stocks. Further, considering recent experimental and observational evidence indicating the interactions of SOC and SIC pools and their likely microbial control, we also investigated how SOC, the soil microbial biomass pool, and SIC are correlated. For SOC stock, there were significant interactions with total SIC and SOC:SIC ratio that differed by tillage intensity. Across the whole soil profile (0¿60¿cm), there was a significantly positive relationship between SOC content and SIC stock that was only present with ploughing. Further, at low SOC:SIC ratios (~0.5¿3.0), while SOC stock was marginally lower under plough, at higher SOC:SIC ratios (~3.1¿10.0), SOC stock was predicted to be up to ~4¿fold greater (4¿kg¿m¿2) with ploughing than the lower intensity tillage treatments. This result highlights a critical SOC-SIC interaction that, depending on tillage intensity, may offset anticipated disturbance-related loss of SOC, and challenges the common perception that tillage consistently reduces SOC. SOC stock was also ~40¿% (0.42¿kg¿m¿2) greater at 0¿10¿cm and ~30¿% (0.2¿kg¿m¿2) greater at 30¿40¿cm under radish cover crop than without. SIC stock differences were correlated with SOC content, tillage intensity and cover cropping. SIC stock was strongly correlated with SOC, with a predicted ~0.3¿1¿kg¿m¿2 increase in SIC stock for ~1¿% increase in SOC. Under radish cover crops and with ploughing, there was ~0.7¿kg¿m¿2 more SIC than under all other conditions. Microbial biomass was positively correlated with SIC stock suggesting a causality that needs experimental testing. Given that reduced tillage is a frequently recommended practice to increase soil carbon storage and given the limited attention that has been paid to the influence of cover cropping on the SIC pool, our results indicate the need for further investigation around the dynamics of SOC and SIC interactions and stabilization processes in calcareous soils and highlights the pitfalls of a one-size-fits-all approach to soil carbon management.

It has been shown that soil management under organic farming can enhance soil organic carbon, thereby mitigating atmospheric greenhouse gas increases, but until now quantitative evaluations based on long term experiments are scarce, especially under Mediterranean conditions. Changes in soil organic carbon (SOC) content were examined in response to organic management with cover crops in a Mediterranean citrus plantation using 21 years of survey data. Soil organic carbon increase was more apparent 5 years after a land management change suggesting that, for citrus plantations on Mediterranean conditions, studies should be longer than five years in duration. Soil organic carbon sequestration rate did not significantly change during the 21 years of observation, with values ranging from -1.10 Mg C ha-1 y-1 to 1.89 Mg C ha-1 y-1. After 21 years, 61 Mg CO2 ha-1 were sequestered in long-lived soil C pools. These findings demonstrate that organic management is an effective strategy to restore or increase SOC content in Mediterranean citrus systems.

Process-based models are useful tools to integrate the effects of detailed agricultural practices, soil characteristics, mass balance, and climate change on soil N2O emissions from soil - plant ecosystems, whereas static, seasonal or annual models often exist to estimate cumulative N2O emissions under data-limited conditions. A study was carried out to compare the capability of four models to estimate seasonal cumulative N2O fluxes from 419 field measurements representing 65 studies across China's croplands. The models were 1) the DAYCENT model, 2) the DNDC model, 3) the linear regression model (YLRM) of Yue et al. (2018), and 4) IPCC Tier 1 emission factors. The DAYCENT and DNDC models estimated crop yields with R2 values of 0.60 and 0.66 respectively, but both models showed significant underestimation for all measurements. The estimated seasonal N2O emissions with R2 of 0.31, 0.30, 0.21 and 0.17 for DAYCENT, DNDC, YLRM, and IPCC, respectively. Based on RMSE, modelling efficiency and bias analysis, YLRM performed well on N2O emission prediction under no fertilization though bias still existed, while IPCC performed well for cotton and rapeseed and DNDC for soybean. The DAYCENT model accurately predicted the emissions with no bias across other crop and fertilization types whereas the DNDC model underestimated seasonal N2O emissions by 0.42 kg N2O-N ha−1 for all observed values. Model evaluation indicated that the DAYCENT and DNDC models simulated temporal patterns of daily N2O emissions effectively, but both models had difficulty in simulating the timing of the N2O fluxes following some events such as fertilization and water regime. According to this evaluation, algorithms for crop production and N2O emission should be improved to increase the accuracy in the prediction of unfertilized fields both for DAYCENT and DNDC. The effects of crop types and management modes such as fertilizations should also be further refined for YLRM.

Significance The climate benefits of cellulosic biofuels have been challenged based on carbon debt, opportunity costs, and indirect land use change, prompting calls for withdrawing support for research and development. Using a quantitative ecosystem modeling approach, which explicitly differentiates primary production, ecosystem carbon balance, and biomass harvest, we show that none of these arguments preclude cellulosic biofuels from realizing greenhouse gas mitigation. Our assessment illustrates how deliberate land use choices support the climate performance of current-day cellulosic ethanol technology and how technological advancements and carbon capture and storage addition could produce several times the climate mitigation potential of competing land-based biological mitigation schemes. These results affirm the climate mitigation logic of biofuels, consistent with their prominent role in many climate stabilization scenarios.

This chapter takes sustainable development as the starting point
\nand focus for analysis. It considers the broad and multifaceted
\nbi-directional interplay between sustainable development, including
\nits focus on eradicating poverty and reducing inequality in their
\nmultidimensional aspects, and climate actions in a 1.5°C warmer world.
\nThese fundamental connections are embedded in the Sustainable
\nDevelopment Goals (SDGs). The chapter also examines synergies
\nand trade-offs of adaptation and mitigation options with sustainable
\ndevelopment and the SDGs and offers insights into possible pathways,
\nespecially climate-resilient development pathways towards a 1.5°C
\nwarmer world.

Significance Most nations recently agreed to hold global average temperature rise to well below 2 °C. We examine how much climate mitigation nature can contribute to this goal with a comprehensive analysis of “natural climate solutions” (NCS): 20 conservation, restoration, and/or improved land management actions that increase carbon storage and/or avoid greenhouse gas emissions across global forests, wetlands, grasslands, and agricultural lands. We show that NCS can provide over one-third of the cost-effective climate mitigation needed between now and 2030 to stabilize warming to below 2 °C. Alongside aggressive fossil fuel emissions reductions, NCS offer a powerful set of options for nations to deliver on the Paris Climate Agreement while improving soil productivity, cleaning our air and water, and maintaining biodiversity.

Abstract As the development of nature‐based solutions (NbS) increases globally, it is important to ensure that projects meet the objective of delivering benefits for biodiversity, alongside tackling societal challenges. However, this is challenging because most NbS projects do not directly monitor ecological outcomes, and those that do often focus on a limited set of metrics. We identify the most informative and feasible above‐ and below‐ground ecological metrics for monitoring the ecological outcomes of NbS. We identify possible biodiversity and soil health metrics using a structured non‐systematic literature review, and rank these using a scoring system to assess their informativeness and feasibility for monitoring. Metrics are categorised into compositional, structural, and functional aspects of biodiversity, and biological, physical and chemical aspects of soil health. We group biodiversity and soil health metrics into Tier 1 (the most informative and feasible metrics), Tier 2 (informative metrics with some limitations in scope or feasibility) and Future metrics (highly informative metrics which are currently less feasible to monitor). Tier 1 metrics collectively address multiple aspects of biodiversity and soil health and are the highest priority for NbS project assessments. For biodiversity, 9 Tier 1, 6 Tier 2 and 15 Future metrics were identified, and for soil health there are 11 Tier 1, 6 Tier 2 and 5 Future metrics. We identify existing standardised methodologies, threshold and reference values for monitoring these metrics, although in many cases, these are not available. Solution . Our study provides practitioners with a framework for selecting optimum metrics for assessing above‐ and below‐ground ecological outcomes of NbS relevant to the location in which they are being implemented. We summarise the relevance of each metric to biodiversity or soil health and provide standardised methodologies for collecting data to support ecological monitoring protocols for NbS projects. The information on each metric is freely available as a searchable online database designed for UK practitioners, but with wider applicability.