Publications

Abstract The Sustainability Nexus Analytics, Informatics, and Data (AID) Programme of the United Nations University (UNU), aims to provide information, data, computational, and analytical tools to support the sustainable management and long-term security of natural resources using a nexus approach. This paper introduces the Soil Health Module of the Sustainability Nexus AID Programme. Healthy soil is crucial for life on Earth, and it is essential for ecosystem services and functioning, access to clean water, socioeconomic structure, biodiversity, and food security for the growing population of the world. Healthy soils contribute to mitigating the effects of climate change and reduce the consequences of extreme events such as flooding and drought. Healthy soils influence the hydrologic cycle by regulating transpiration, water infiltration, and soil water evaporation affecting land–atmosphere interactions. The Soil Health Module of the UNU Sustainability Nexus AID Programme aims to evolve into the ultimate focal point, supporting a diverse array of stakeholders with state-of-the-art data and tools that are essential for soil health monitoring and projection. This paper discusses the importance of adopting a nexus approach for ensuring soil health, explores the AID tools currently at our disposal for quantifying and predicting soil health, and concludes with recommendations for future effort and direction within the Sustainability Nexus AID Programme concerning soil health.

Humankind faces a Triple Challenge: averting dangerous climate change, reversing biodiversity loss, and supporting the wellbeing of a growing population. Action to address each of these issues is inherently dependent on action to address the others. Local, national, and international policy goals on climate change, biological diversity, and human wellbeing have been set. Current implementation measures are insufficient to meet these goals, but the Triple Challenge can still be met if governments, corporations, and other stakeholders take a holistic perspective on management of land and waters. To inform this effort, we identify a set of priority policy responses drawn from recent international assessments that, whilst not being the only potential solutions, can form the core of such a holistic approach. We do this through an iterative process using three methodological approaches: (i) structured literature review; (ii) deliberative expert analysis; and (iii) wider consultation, before synthesizing into this paper. Context-appropriate implementation of responses will be needed to capitalize on potential policy synergies and to ensure that unavoidable trade-offs between management of land and waters for climate mitigation, biodiversity restoration, and human wellbeing outcomes are made explicit. We also set out four approaches to managing trade-offs that can promote fair and just transitions: (1) social and economic policy pivoting towards ‘inclusive wealth’; (2) more integrated policymaking across the three areas; (3) ‘Triple Challenge dialogues’ among state and non-state actors; and (4) a new research portfolio to underpin (1), (2), and (3). Multiple recent global assessments provide a strong scientific basis for action on each of the three aspects of the Triple Challenge – climate, biodiversity, and human wellbeing (with a focus on food and nutrition) – but they do not provide an integrated perspective on how to address them simultaneously.Synthesis of these assessments identifies a portfolio of five core policy responses that deliver across the Triple Challenge: (i) rapidly cutting fossil fuel use; (ii) promoting sustainable, healthy diets; (iii) increasing food productivity and cutting food loss and waste; (iv) implementing nature-based solutions at scale; and (v) strengthening governance and management of land and waters.Even with widespread implementation of that portfolio, trade-offs between climate, biodiversity, and wellbeing outcomes might be unavoidable. Policymakers, researchers, and other actors should explicitly identify such trade-offs, and take steps to ensure management priorities are set through equitable dialogue processes informed by integrated research. Multiple recent global assessments provide a strong scientific basis for action on each of the three aspects of the Triple Challenge – climate, biodiversity, and human wellbeing (with a focus on food and nutrition) – but they do not provide an integrated perspective on how to address them simultaneously. Synthesis of these assessments identifies a portfolio of five core policy responses that deliver across the Triple Challenge: (i) rapidly cutting fossil fuel use; (ii) promoting sustainable, healthy diets; (iii) increasing food productivity and cutting food loss and waste; (iv) implementing nature-based solutions at scale; and (v) strengthening governance and management of land and waters. Even with widespread implementation of that portfolio, trade-offs between climate, biodiversity, and wellbeing outcomes might be unavoidable. Policymakers, researchers, and other actors should explicitly identify such trade-offs, and take steps to ensure management priorities are set through equitable dialogue processes informed by integrated research.

Abstract. In this forum paper we discuss how soil scientists can help to reach the recently adopted UN Sustainable Development Goals (SDGs) in the most effective manner. Soil science, as a land-related discipline, has important links to several of the SDGs, which are demonstrated through the functions of soils and the ecosystem services that are linked to those functions (see graphical abstract in the Supplement). We explore and discuss how soil scientists can rise to the challenge both internally, in terms of our procedures and practices, and externally, in terms of our relations with colleague scientists in other disciplines, diverse groups of stakeholders and the policy arena. To meet these goals we recommend the following steps to be taken by the soil science community as a whole: (i) embrace the UN SDGs, as they provide a platform that allows soil science to demonstrate its relevance for realizing a sustainable society by 2030; (ii) show the specific value of soil science: research should explicitly show how using modern soil information can improve the results of inter- and transdisciplinary studies on SDGs related to food security, water scarcity, climate change, biodiversity loss and health threats; (iii) take leadership in overarching system analysis of ecosystems, as soils and soil scientists have an integrated nature and this places soil scientists in a unique position; (iii) raise awareness of soil organic matter as a key attribute of soils to illustrate its importance for soil functions and ecosystem services; (iv) improve the transfer of knowledge through knowledge brokers with a soil background; (v) start at the basis: educational programmes are needed at all levels, starting in primary schools, and emphasizing practical, down-to-earth examples; (vi) facilitate communication with the policy arena by framing research in terms that resonate with politicians in terms of the policy cycle or by considering drivers, pressures and responses affecting impacts of land use change; and finally (vii) all this is only possible if researchers, with soil scientists in the front lines, look over the hedge towards other disciplines, to the world at large and to the policy arena, reaching over to listen first, as a basis for genuine collaboration.

ABSTRACT Biochar amendment is one of the most promising agricultural approaches to tackle climate change by enhancing soil carbon (C) sequestration. Microbial‐mediated decomposition processes are fundamental for the fate and persistence of sequestered C in soil, but the underlying mechanisms are uncertain. Here, we synthesise 923 observations regarding the effects of biochar addition (over periods ranging from several weeks to several years) on soil C‐degrading enzyme activities from 130 articles across five continents worldwide. Our results showed that biochar addition increased soil ligninase activity targeting complex phenolic macromolecules by 7.1%, but suppressed cellulase activity degrading simpler polysaccharides by 8.3%. These shifts in enzyme activities explained the most variation of changes in soil C sequestration across a wide range of climatic, edaphic and experimental conditions, with biochar‐induced shift in ligninase:cellulase ratio correlating negatively with soil C sequestration. Specifically, short‐term (<1 year) biochar addition significantly reduced cellulase activity by 4.6% and enhanced soil organic C sequestration by 87.5%, whereas no significant responses were observed for ligninase activity and ligninase:cellulase ratio. However, long‐term (≥1 year) biochar addition significantly enhanced ligninase activity by 5.2% and ligninase:cellulase ratio by 36.1%, leading to a smaller increase in soil organic C sequestration (25.1%). These results suggest that shifts in enzyme activities increased ligninase:cellulase ratio with time after biochar addition, limiting long‐term soil C sequestration with biochar addition. Our work provides novel evidence to explain the diminished soil C sequestration with long‐term biochar addition and suggests that earlier studies may have overestimated soil C sequestration with biochar addition by failing to consider the physiological acclimation of soil microorganisms over time.

<p>Selective logging is the practice of extracting selected commercial trees from natural production forests. The intensity of logging correlates with a reduction in biodiversity, wood production and biomass stocks. Less is known about the relationship of logging to soil organic carbon (SOC) and how it changes or recovers over time. Empirical measurements in Borneo provided SOC, soil respiration, aboveground and belowground net primary productivity (NPP) from intact old-growth forest (OGF) as well as from moderately to heavily logged (LOG) forest sites. Soil carbon (C) content and heterotrophic respiration (R<sub>h</sub>) was higher in LOG sites than in OGF sites. Moderately logged forest (logged > 10 years ago) contained more SOC than heavily logged forest (logged approx. 7 years ago). NPP was used to estimate the C input to the soil. All these data were used to test the biochemical model ECOSSE (<strong>E</strong>stimating <strong>C</strong>arbon in <strong>O</strong>rganic <strong>S</strong>oils – <strong>S</strong>equestration and <strong>E</strong>missions) to calculate SOC for the study sites. The model performed well in simulating the soil respiration of OGF and generated acceptable results for LOG sites in the validation process. The results for logged forests showed an increase in R<sub>h</sub> over the first 15 years, with some sites showing either a further increase over the next 15 years or stabilizing at a higher level compared to pre-disturbance conditions for other sites. However, for all modelled cases, a break was observed after 30 years, when R<sub>h</sub> decreased to a lower level (but not as low as for OGF) before reaching a new equilibrium. At the same time, SOC begins to increase. Spatial modelling showed the results for Borneo under logged conditions and the potential of storing C if logging was reduced. Only 22% of Borneo is under old-growth forest; the results show moderate to high C losses if this region is subjected to logging. Overall, the results show the disturbance of SOC and Rh through logging over periods longer than 30 years.</p>