Potential synergies between existing multilateral environmental agreements in the implementation of Land Use, Land Use Change and Forestry activities

There is potential for synergy between the global environmental conventions on climate change, biodiversity and desertification: changes in land management and land use undertaken to reduce net greenhouse gas emissions can simultaneously deliver positive outcomes for conservation of biodiversity, and mitigation of desertification and land degradation. However, while there can be complementarities between the three environmental goals, there are often tradeoffs. Thus, the challenge lies in developing land use policies that promote optimal environmental outcomes, and in implementing these locally to promote sustainable development. The paper considers synergies and tradeoffs in implementing land use measures to address the objectives of the three global environmental conventions, both from an environmental and economic perspective. The intention is to provide environmental scientists and policy makers with a broad overview of these considerations, and the benefits of addressing the conventions simultaneously.Climate change, LULUCF, Biodiversity, Desertification, Sustainable development.

Meta-analysis quantifying the potential of dietary additives and rumen modifiers for methane mitigation in ruminant production systems

Increasingly countries are seeking to reduce emission of greenhouse gases from the agricultural industries, and livestock production in particular, as part of their climate change management. While many reviews update progress in mitigation research, a quantitative assessment of the efficacy and performance-consequences of nutritional strategies to mitigate enteric methane (CH4) emissions from ruminants has been lacking. A meta-analysis was conducted based on 108 refereed papers from recent animal studies (2000-2020) to report effects on CH4 production, CH4 yield and CH4 emission intensity from 8 dietary interventions. The interventions (oils, microalgae, nitrate, ionophores, protozoal control, phytochemicals, essential oils and 3-nitrooxypropanol). Of these, macroalgae and 3-nitrooxypropanol showed greatest efficacy in reducing CH4 yield (g CH4/kg of dry matter intake) at the doses trialled. The confidence intervals derived for the mitigation efficacies could be applied to estimate the potential to reduce national livestock emissions through the implementation of these dietary interventions

Mobilizing Sustainable Bioenergy Supply Chains

Analysis of the five globally significant supply chains conducted by IEA Bioenergy inter-Task teams – boreal and temperate forests, agricultural crop residues, biogas, lignocellulosic crops, and cultivated grasslands and pastures in Brazil – has confirmed that feedstocks produced using logistically efficient production systems can be mobilized to make significant contributions to achieving global targets for bioenergy. However, the very significant challenges identified in this report indicate that changes by all key members of society in public and private institutions and along the whole length of supply chains from feedstock production to energy product consumption are required to mobilize adequate feedstock resources to make a sustainable and significant contribution to climate change mitigation and provide the social and economic services possible. Notably, this report reveals that all globally significant bioenergy development has been underpinned by political backing, which is necessary for passing legislation in the form of mandates, renewable energy portfolios, carbon trading schemes, and the like. The mobilization potential identified in this report will depend on even greater policy support than achieved to date internationally.JRC.F.8-Sustainable Transpor

Restoring Degraded Lands

Land degradation continues to be an enormous challenge to human societies, reducing food security, emitting greenhouse gases and aerosols, driving the loss of biodiversity, polluting water, and undermining a wide range of ecosystem services beyond food supply and water and climate regulation. Climate change will exacerbate several degradation processes. Investment in diverse restoration efforts, including sustainable agricultural and forest land management, as well as land set aside for conservation wherever possible, will generate co-benefits for climate change mitigation and adaptation and morebroadly for human and societal well-being and the economy. This review highlights the magnitude of the degradation problem and some of the key challenges for ecological restoration. There are biophysical as well as societal limits to restoration. Better integrating policies to jointly address poverty, land degradation, and greenhouse gas emissions and removals is fundamental to reducing many existing barriers and contributing to climate-resilient sustainable development

Storage and stability of soil organic carbon down the profiles under native woodland, native pastures and cultivation

Soils are widely recognized as having potential to sequester significant amounts of carbon (C). There is much speculation that deeper soil layers can store significant amounts of C in a relatively stable form and that land use can influence soil organic carbon (SOC) stocks at depth. Our understanding of the potential for subsoils to store C in the long term is however limited here in Australia, as little work has been done to quantify C stocks, and the available studies on C dynamics have been mainly focused in surface soils (30 cm or less), and conducted from a narrow range of management options. The main aim of this research was to examine SOC stocks and stability down texturally contrasted soil layers (up to 0.80 m) under three major land uses, namely native woodland, native pastures and cultivation, in the Northern Tablelands of New South Wales, Australia. Specifically, this study examined the effects of land use on a) the quantity of total SOC stocks down the profiles; b) dissolved organic carbon (DOC) concentrations down the profiles; c) the amounts and composition of dissolved organic matter (DOM) extracted from different litter types; b) quantity and quality of SOC among soil particle size fractions; c) SOC mineralization dynamics including C pools and turnover kinetics; and d) C and nitrogen (N) mineralization dynamics of decomposing plant litter and interactions with initial biochemical composition of litter. Understanding C stocks and organic matter stability in soils taking into account deeper soil layers as affected by land use will identify the most effective land use for carbon sequestration and thereby inform land use decisions in the northern region of NSW Australia. Strong differences in SOC stocks between land uses were only apparent in the surface 20 cm, with native pastures and cultivation which were statistically similar to each other containing on average 9 and 11 t/ha less C than native woodland. Significantly larger SOC stocks in surface soils under native woodland may be partly attributed to more lignin-rich recalcitrant above ground litter inputs compared with the other two land uses. The combined subsoil (20 to 80 cm) layers contained 40 % of the total profile SOC stocks across all land uses, demonstrating that substantial amounts of SOC stocks reside in deeper layers and so the importance of preserving it. The relative proportion of aromatic C in dissolved organic matter (DOM) extracted from litter was highest under native woodland, followed by native pasture then cultivation indicating qualitative differences in DOM fractions which may in turn influence biodegradability of DOM among litter types. DOC represented between 0.01 and 0.1 % of total SOC down the soil profiles and across all land uses showing that the contribution of DOC to C stocks was relatively small. Native woodland soils were associated with consistently wider C:N ratios in the particulate organic matter (POM) fraction throughout the soil profile compared with native pastures and cultivation which differed between each other in the top 50 cm. The result indicated differences in the quality of organic matter inputs (litter) entering the POM fraction with native woodland soils associated with less easily decomposed inputs due to their inherent chemical composition. Consequently, native woodland showed the least decline in particulate organic carbon (POC) with soil depth compared with the other two land uses. The proportion of MOC to the total SOC increased with soil depth indicating that subsurface C was more protected than surface C probably due to mineral association with clayey subsoils. Compared with native pastures and cultivation which were largely similar, native woodland soils contained significantly larger amounts of MOC in all soil depths suggesting that C was more physically protected from microbial attack. SOC mineralization kinetics over 419 days was well described by decomposition of a single pool. Compared with native pastures and cultivation, native woodland had larger amounts of the active C pools in all soil depths which were mainly related to larger amounts of labile substrates mainly DOC and POC down the profiles. The decomposition rate of the active C pool, measured by laboratory incubations, was strongly dependent on soil depth with turnover of 66 and 47 days in surface and subsoils respectively. Shorter turnover of active C pool in subsoils compared with surface soils may be linked to destabilization of active C stores when environmental constraints on decomposition which might inhibit decomposition in the undisturbed profile are removed following incubation under similar conditions in the laboratory. Consequently, it is important that the current C stores remain undisturbed. For all litter types, the active C pool whose decay rate constants ranged from 0.072 d-1 to 0.805 d-1, initially constituted 80 % of the litter mass. The decomposition rate of the slow C pool in litter was strongly and negatively correlated with the initial lignin:N ratio of plant litter suggesting that the interaction between these two litter quality variables had important controls over litter decomposition. Compared with other litter types, above and below ground litter from native woodland had higher initial lignin:N ratio and were associated with more stable slow C pools with longer half lives of 109 and 446 days respectively. The above and below ground litter components had distinct N mineralization patterns during the early stages of incubation as influenced by the initial biochemical composition of plant litter namely C:N ratio, % lignin and % water soluble carbon (WSC). Our results suggest that the biochemically recalcitrant lignin influenced the susceptibility of substrates to microbial attack and thereafter a demand for N by microbial decomposers. However, the subsequent release of N from substrates depended on the C:N ratio. The results of this thesis are relevant to landholders, natural resource managers and policy makers as they inform that native woodland soil has an important role in storing a) larger SOC stocks in surface (20 cm) layers compared with native pastures and cultivation which were generally similar, b) relatively less decomposable C down the soil profiles as larger amounts of C are associated with the mineral fraction, and c) more slowly decomposing organic matter inputs which were characterized by relatively stable slow C pools in litter compared with native pastures and cultivation in the northern region of NSW Australia. Key future research areas arising from this thesis include to: a) investigate land use effects on total SOC stocks in soil profiles using increased intensity of soil sampling in order to represent spatial variation and increase capacity to detect differences in total SOC especially where differences in C might be small such as in non-wooded land uses, b) compare land use effect on DOC storage at various depths during crop/pasture growing season as the living plant biomass may influence DOC concentrations, c) determine the stability of DOC derived from both soils and litter in order to determine its long term dynamics in soils, d) determine the long term stability of soil slow C pool and investigate the mechanisms by which C might be stabilized including the contribution of char C at various depths under the three land uses, e) determine the mechanism by which lignin and N interact to influence decomposability of litter, and f) understand the mechanism of SOC and N stabilization

Bioenergy for climate change mitigation: Scale and sustainability

Many global climate change mitigation pathways presented in IPCC assessment reports rely heavily on the deployment of bioenergy, often used in conjunction with carbon capture and storage. We review the literature on bioenergy use for climate change mitigation, including studies that use top-down integrated assessment models or bottom-up modelling, and studies that do not rely on modelling. We summarize the state of knowledge concerning potential co-benefits and adverse side effects of bioenergy systems and discuss limitations of modelling studies used to analyse consequences of bioenergy expansion. The implications of bioenergy supply on mitigation and other sustainability criteria are context dependent and influenced by feedstock, management regime, climatic region, scale of deployment and how bioenergy alters energy systems and land use. Depending on previous land use, widespread deployment of monoculture plantations may contribute to mitigation but can cause negative impacts across a range of other sustainability criteria. Strategic integration of new biomass supply systems into existing agriculture and forest landscapes may result in less mitigation but can contribute positively to other sustainability objectives. There is considerable variation in evaluations of how sustainability challenges evolve as the scale of bioenergy deployment increases, due to limitations of existing models, and uncertainty over the future context with respect to the many variables that influence alternative uses of biomass and land. Integrative policies, coordinated institutions and improved governance mechanisms to enhance co-benefits and minimize adverse side effects can reduce the risks of large-scale deployment of bioenergy. Further, conservation and efficiency measures for energy, land and biomass can support greater flexibility in achieving climate change mitigation and adaptation

Bioenergy for climate change mitigation: Scale and sustainability

Many global climate change mitigation pathways presented in IPCC assessment reports rely heavily on the deployment of bioenergy, often used in conjunction with carbon capture and storage. We review the literature on bioenergy use for climate change mitigation, including studies that use top-down integrated assessment models or bottom-up modelling, and studies that do not rely on modelling. We summarize the state of knowledge concerning potential co-benefits and adverse side effects of bioenergy systems and discuss limitations of modelling studies used to analyse consequences of bioenergy expansion. The implications of bioenergy supply on mitigation and other sustainability criteria are context dependent and influenced by feedstock, management regime, climatic region, scale of deployment and how bioenergy alters energy systems and land use. Depending on previous land use, widespread deployment of monoculture plantations may contribute to mitigation but can cause negative impacts across a range of other sustainability criteria. Strategic integration of new biomass supply systems into existing agriculture and forest landscapes may result in less mitigation but can contribute positively to other sustainability objectives. There is considerable variation in evaluations of how sustainability challenges evolve as the scale of bioenergy deployment increases, due to limitations of existing models, and uncertainty over the future context with respect to the many variables that influence alternative uses of biomass and land. Integrative policies, coordinated institutions and improved governance mechanisms to enhance co-benefits and minimize adverse side effects can reduce the risks of large-scale deployment of bioenergy. Further, conservation and efficiency measures for energy, land and biomass can support greater flexibility in achieving climate change mitigation and adaptation

Bioenergy for climate change mitigation : scale and sustainability

Funding Information: The authors are grateful for comments from three reviewers and the editor. The views expressed in this article are those of the authors alone.Peer reviewedPublisher PD

Defining national net zero goals is critical for food and land use policy

The identification of agriculture and land use configurations that achieve net zero (NZ) greenhouse gas emissions is critical to inform appropriate land use and food policy, yet national NZ targets lack consistent definitions. Here, 3000 randomised scenarios projecting future agricultural production and compatible land use combinations in Ireland were screened using ten NZ definitions. When aggregating carbon dioxide, methane, and nitrous oxide emissions using various methods, 1–85% of scenarios met NZ criteria. Despite considerable variation, common actions emerged across definitions, including high rates of afforestation, organic soil re-wetting, and cattle destocking. Ambitious technical abatement of agricultural emissions moderated, but could not substitute, these actions. With abatement, 95th percentile milk output varied from 11–91% of 2021 output, but was associated with reductions of up to 98% in suckler-beef production, and a 47–387% increase in forest cover. Achieving NZ will thus require transformation of Ireland’s land sector. Lagging land use change effects require urgent action, but sustaining a just transition will require visioning of future NZ land use combinations supporting a sustainable and resilient food system, alongside an expanding circular bioeconomy. We provide new insight into the sensitivity of such visioning to NZ definitions, pointing to an urgent need for international consensus on the accounting of methane emissions in NZ targets