ALBERT

Description: Dissolved carbon leaching in and from soils plays an important role in C transport along the terrestrial-aquatic continuum. However, a global overview and analysis of dissolved carbon in soil solutions, covering a wide range of vegetation types and climates, is lacking. We compiled a global database on annual average dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in soil solutions, including potential governing factors, with 762 entries from 351 different sites covering a range of climate zones, land cover types and soil classes. Using this database we develop regression models to calculate topsoil concentrations, and concentrations vs. depth in the subsoil at the global scale. For DIC, the lack of a roportional globally distributed cover inhibits analysis on a global scale. For DOC, annual average concentrations range from 1.7 to 88.3 (median=25.27) mg C/L for topsoils (n=255) and from 0.42 to 372.1 (median=5.50) mg C/L for subsoils (n=285, excluding lab incubations). Highest topsoil values occur in forests of cooler, humid zones. In topsoils, multiple regression showed that precipitation is the most significant factor. Our global topsoil DOC model (R2=0.36) uses precipitation, soil class, climate zone and land cover type as model factors. Our global subsoil model describes DOC concentrations vs. depth for different USDA soil classes (overall R2=0.45). Highest subsoil DOC concentrations are calculated for Histosols.

Description: In this report document, we discuss the approach to a global integrated nitrogen assessment model chain allowing to evaluate the consequences of different socio-economic drivers (scenarios) and N mitigation management in terms of: (i) benefits, including food, feed, fibre (wood) and energy production and (ii) threats, including pollutant and greenhouse gas emissions, affecting the quality of air, soil and water and related climate, human health and biodiversity impacts and (iii) cost-effectiveness. This is done by addressing: •The overall modelling approach, including (i) the type of models that are neededto simulate nitrogen benefits and threats and (ii) the model linkages needed toenable a consistent multi-model approach in response to a consistent set ofscenarios of drivers (population development, income etc.) and N mitigationmeasures.•The modelling practice including (i) the modelling approaches, distinguishingbetween empirical and process-based models, and (ii) the available models thatwould serve an integrated global scale nitrogen assessment, considering thevariety of impacts and scales.•A modelling protocol of the involved models including information on: (i) themodels involved, (ii) basic agreements on base year (2010), spatial extent andresolution, temporal extent and resolution, (iii) scenarios, (iv) model outputsand (v) model linkages.•A database platform for the INMS model inputs and outputs.

Description: Input–output estimates of nitrogen on cropland are essential for improving nitrogen management and better understanding the global nitrogen cycle. Here, we compare 13 nitrogen budget datasets covering 115 countries and regions over 1961–2015. Although most datasets showed similar spatiotemporal patterns, some annual estimates varied widely among them, resulting in large ranges and uncertainty. In 2010, global medians (in TgN yr−1) and associated minimum–maximum ranges were 73 (64–84) for global harvested crop nitrogen; 161 (139–192) for total nitrogen inputs; 86 (68–97) for nitrogen surplus; and 46% (40–53%) for nitrogen use efficiency. Some of the most uncertain nitrogen budget terms by country showed ranges as large as their medians, revealing areas for improvement. A benchmark nitrogen budget dataset, derived from central tendencies of the original datasets, can be used in model comparisons and inform sustainable nitrogen management in food systems.

Description: The human-earth system is confronted with the challenge of providing a range of resources for a growing and more prosperous world population while simultaneously reducing environmental degradation. The Sustainable Development Goals and the Planetary Boundaries define targets to manage this challenge. Many of these are linked to the land system, such as biodiversity, water, food, nutrients and climate, and are strongly interconnected. A key question is how measures can be designed in the context of multi-dimensional sustainability targets to exploit synergies. To address this, a nexus approach is adopted that acknowledges the interconnectedness between the important sub-systems water, land, food, and climate. This study quantifies synergies and trade-offs from ambitious interventions in different components of this Water-Land-Food-Climate nexus at the global scale. For this purpose, a set of six harmonized scenarios is simulated with the MAgPIE and IMAGE models. The multi-model approach improves robustness of the results while shedding light on variations coming from different modelling approaches. Our results show that measures in the food component towards healthy diets with low meat consumption have synergies with all other nexus dimensions: Increased natural land improving terrestrial biodiversity (+4% to +8%), lower greenhouse gas emissions from land (-45% to -58%), reduced irrigation water withdrawals to protect or restore hydrological environmental flows (-3% to -24%), and reductions in nitrogen surpluses (-23% to -35%). Climate mitigation measures in line with the Paris Agreement have trade-offs with the water and food components of the nexus, as they adversely affect irrigation water withdrawals (+5% to +30% in 2050 compared to reference scenario) and food prices (+1% to +20%). The analysis of a scenario combining all measures reveals how certain measures are in conflict while others reinforce each other. This study provides an example of a nexus approach to scenario analysis providing input to the next generation of pathways aiming to achieve multiple dimensions of sustainable development.