Abstract Societal activities massively alter the global carbon (C) cycle, thereby driving global climate heating. Socioeconomic material stocks – e.g., in buildings and infrastructures – have been ...identified as a C pool that can potentially store increasing amounts of C, thereby keeping C away from the atmosphere. However, little is known about the size, composition, distribution and development of global socioeconomic C stocks. Based on an established economy-wide C accounting approach from sociometabolic research, we consistently and comprehensively quantified the C contained in eight components of socioeconomic stocks in the period 1900-2015 at the level of nine world regions. We discern inert (aggregates & other gravel) and ‘active’ climate-relevant (i.e., biomass and fossil-fuel based) C pools. We find that global active components of socioeconomic C stocks grew by a factor of 9, from 1.9 (1.5-2.2) Pg of carbon (PgC) to 16.8 (13.7-20.2) PgC. The inert socioeconomic C stock in aggregates & other gravel amounted to 25.2 (6.1-48.0) PgC in 2015, however with high uncertainties. Absolute annual Net Additions to Stock (NAS) of active stock components was 0.49 (0.40-0.59) PgC/yr which equalled 5% of the C emissions from fossil fuel combustion and industrial processes. However, raising NAS of components with biomass feedstock that sequester C from the atmosphere comes with biodiversity and food security trade-offs. This study contributes to a holistic perspective on social and natural C stocks that acknowledges their interactions. The global socioeconomic C stock reached a geologically relevant extent (approximately the size of C in coasts) and should therefore be integrated in the assessments of the global C cycle to acknowledge the Anthropocene.
Short rotation plantations are often considered as holding vast potentials for future global bioenergy supply. In contrast to raising biomass harvests in forests, purpose‐grown biomass does not ...interfere with forest carbon (C) stocks. Provided that agricultural land can be diverted from food and feed production without impairing food security, energy plantations on current agricultural land appear as a beneficial option in terms of renewable, climate‐friendly energy supply. However, instead of supporting energy plantations, land could also be devoted to natural succession. It then acts as a long‐term C sink which also results in C benefits. We here compare the sink strength of natural succession on arable land with the C saving effects of bioenergy from plantations. Using geographically explicit data on global cropland distribution among climate and ecological zones, regionally specific C accumulation rates are calculated with IPCC default methods and values. C savings from bioenergy are given for a range of displacement factors (DFs), acknowledging the varying efficiency of bioenergy routes and technologies in fossil fuel displacement. A uniform spatial pattern is assumed for succession and bioenergy plantations, and the considered timeframes range from 20 to 100 years. For many parameter settings—in particular, longer timeframes and high DFs—bioenergy yields higher cumulative C savings than natural succession. Still, if woody biomass displaces liquid transport fuels or natural gas‐based electricity generation, natural succession is competitive or even superior for timeframes of 20–50 years. This finding has strong implications with climate and environmental policies: Freeing land for natural succession is a worthwhile low‐cost natural climate solution that has many co‐benefits for biodiversity and other ecosystem services. A considerable risk, however, is C stock losses (i.e., emissions) due to disturbances or land conversion at a later time.
How can spare cropland be used more efficiently in terms of climate change mitigation? By growing short rotation coppice for bioenergy or allowing cropland to revert to its natural state. We show that the more beneficial option depends on the timeframe considered, biophysical conditions in the considered region, upstream emissions of fuel supply, and the efficiency of the particular bioenergy route in displacing fossil fuels.
Abstract
Emissions from agricultural activities constitute 11% of global greenhouse gas emissions and are hard to abate. Here, we present and analyze a consistent empirical assessment of global ...emissions from agricultural activities from 1910–2015. Agricultural emissions increased 3.5-fold from 1910–2015, from 1.9 to 6.7 GtCO
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emissions, emissions from enteric fermentation and from livestock products contributed the highest fractions of emissions by gases, processes, and products, respectively. A decomposition analysis quantifies the contribution of major drivers of agricultural emissions dynamics. It reveals that globally and across the entire period, changes in population, agricultural production per capita (‘output’), regional distribution of production (‘regional mix’), and composition of final products (‘product mix’, i.e. a shift towards livestock production) all contributed to increasing agricultural emissions. Conversely, declining emissions per unit of production (‘emissions intensity’), particularly for livestock, partly counterbalanced the emissions increase. Significant variations prevail across regions and time periods. Most notably, the composition of final products counteracted agricultural emissions increase from 1910–1950, but growing livestock production has become an increasingly important driver of emissions growth in more recent periods. This finding unravels that increases in livestock production offset the improvements in emissions intensity of industrial agricultural intensification. Our findings underscore the large potential of reducing livestock production and consumption for mitigating the climate impacts of agriculture.
Global bioenergy potentials have been the subject of extensive research and continued controversy. Due to vast uncertainties regarding future yields, diets and other influencing parameters, estimates ...of future agricultural biomass potentials vary widely. Most scenarios compatible with ambitious climate targets foresee a large expansion of bioenergy, mainly from energy crops that needs to be kept consistent with projections of agriculture and food production. Using the global biomass balance model BioBaM, we here present an assessment of agricultural bioenergy potentials compatible with the Food and Agriculture Organization's (2018) 'Alternative pathways to 2050' projections. Mobilizing biomass at larger scales may be associated with systemic feedbacks causing greenhouse gas (GHG) emissions, e.g. crop residue removal resulting in loss of soil carbon stocks and increased emissions from fertilization. To assess these effects, we derive 'GHG cost supply-curves', i.e. integrated representations of biomass potentials and their systemic GHG costs. Livestock manure is most favourable in terms of GHG costs, as anaerobic digestion yields reductions of GHG emissions from manure management. Global potentials from intensive livestock systems are about 5 EJ/yr. Crop residues can provide up to 20 EJ/yr at moderate GHG costs. For energy crops, we find that the medium range of literature estimates (∼40 to 90 EJ/yr) is only compatible with FAO yield and human diet projections if energy plantations expand into grazing areas (∼4-5 million km2) and grazing land is intensified globally. Direct carbon stock changes associated with perennial energy crops are beneficial for climate mitigation, yet there are-sometimes considerable-'opportunity GHG costs' if one accounts the foregone opportunity of afforestation. Our results indicate that the large potentials of energy crops foreseen in many energy scenarios are not freely and unconditionally available. Disregarding systemic effects in agriculture can result in misjudgement of GHG saving potentials and flawed climate mitigation strategies.
A better understanding of the global carbon cycle as well as of climate change mitigation options such as carbon sequestration requires the quantification of natural and socioeconomic stocks and ...flows of carbon. A so-far under-researched aspect of the global carbon budget is the accumulation of carbon in long-lived products such as buildings and furniture. We present a comprehensive assessment of global socioeconomic carbon stocks and the corresponding in- and outflows during the period 1900-2008. These data allowed calculation of the annual carbon sink in socioeconomic stocks during this period. The study covers the most important socioeconomic carbon fractions, i.e. wood, bitumen, plastic and cereals. Our assessment was mainly based on production and consumption data for plastic, bitumen and wood products and the respective fractions remaining in stocks in any given year. Global socioeconomic carbon stocks were 2.3 GtC in 1900 and increased to 11.5 GtC in 2008. The share of wood in total C stocks fell from 97% in 1900 to 60% in 2008, while the shares of plastic and bitumen increased to 16% and 22%, respectively. The rate of gross carbon sequestration in socioeconomic stocks increased from 17 MtC yr−1 in 1900 to a maximum of 247 MtC yr−1 in 2007, corresponding to 2.2%-3.4% of global fossil-fuel-related carbon emissions. We conclude that while socioeconomic carbon stocks are not negligible, their growth over time is not a major climate change mitigation option and there is an only modest potential to mitigate climate change by the increase of socioeconomic carbon stocks.
Assessing progress towards environmental sustainability requires a robust and systematic knowledge base. Economy-wide material flow accounting (ew-MFA) is an established method to monitor resource ...use across scales and its headline indicators are widely used in policy. However, ew-MFA is currently limited by its empirical focus on annual flows of material and energy, because it neglects the pivotal role of in-use material stocks of manufactured capital. Explicitly integrating in-use stocks enables new insights into a range of Ecological Economics' topics, such as the biophysical assessment of socio-economic systems, the circular economy and stock-flow consistent scenarios.
Herein, we conceptually and practically expand the ew-MFA framework towards jointly addressing material flows, in-use stocks of manufactured capital and waste, using a fully consistent dynamic model of Material Inputs, Stocks and Outputs (MISO-model). We review the stock modelling literature, propose a novel distinction of stock-driven versus inflow-driven approaches and situate the MISO-model as the latter. We then investigate the global dynamics of socio-metabolic flows and in-use stocks from 1900 to 2014, explore model sensitivities and quantify and attribute uncertainty. Two exemplary scenarios are presented. Through these innovations for ew-MFA, we enable a dynamic and comprehensive assessment of resource use, stocks and all wastes in the socio-economic metabolism.
•Use-phase, in-use stock dynamics, waste and recycling crucial next steps for ew-MFA•Review of stock-modelling yields new classification: stock-driven vs. inflow-driven•Dynamic inflow-driven model of Material Inputs, Stocks and Outputs (MISO-model v1)•Global in-use stocks increase 26-fold to 928 Gt ± 5% between 1900 and 2014•Two exemplary scenarios on the importance of stock dynamics are shown
The world population is expected to rise to 9.7 billion by 2050 and to ~11 billion by 2100, and securing its healthy nutrition is a key concern. As global fertile land is limited, the question arises ...whether growth in food consumption associated with increased affluence surmounts increases in land-use efficiency (measured as food supply per cropland area) associated with technological progress. Furthermore, substantial inequalities prevail in the global food system: While overly rich diets represent a serious health issue for many of the world’s most affluent inhabitants and constitute a critical climate-change driver, undernourishment and hunger still threaten a considerable fraction of the world population, mostly in low-income countries. We here analyze trajectories in cropland demand and their main basic drivers food consumption (measured by a food index reflecting the share of animal products in diets) and land-use efficiency, for 123 countries (clustered in four income groups, covering 94% of the world population). We cover the period 1990–2013 and assess if these trajectories are associated with changes in inequality between countries. We find that while all groups of countries converged towards the high level of the per-capita food consumption of high-income countries, differences between income groups remained pronounced. Overall, cropland demand per capita declined over the entire period in all regions except low income countries, resulting in a tendency towards global convergence. However, the trend slowed in the last years. In contrast, land-use efficiency increased in all income groups with a similar trend, hence international inequalites in land-use efficiency remained almost unaltered. Because population and food requirements per capita are expected to grow in all income groups except the richest ones, failure to improve land efficiency sufficiently could lead to a less unequal but at the same time less ecologically sustainable world. Avoiding such outcomes may be possible by reducing the consumption of animal products in the richer countries and raising land-use efficiency in the poorer countries.
To date the concept of the bioeconomy—an economy based primarily on biogenic instead of fossil resources—has largely been associated with visions of “green growth” and the advancement of ...biotechnology and has been framed from within an industrial perspective. However, there is no consensus as to what a bioeconomy should effectively look like, and what type of society it would sustain. In this paper, we identify different types of narratives constructed around this concept and carve out the techno-political implications they convey. We map these narratives on a two-dimensional option space, which allows for a rough classification of narratives and their related imaginaries into four paradigmatic quadrants. We draw the narratives from three different sources: (i) policy documents of national and supra-national authorities; (ii) stakeholder interviews; and (iii) scenarios built in a biophysical modelling exercise. Our analysis shows that there is a considerable gap between official policy papers and visions supported by stakeholders. At least in the case of Austria there is also a gap between the official strategies and the option space identified through biophysical modelling. These gaps testify to the highly political nature of the concept of the bioeconomy and the diverging visions of society arising from it.
Agriculture is an important contributor to greenhouse gas (GHG) emissions. While the development of agricultural GHG emissions on national and global scales is well studied for the last three to six ...decades, little is known about their trajectory and drivers over longer periods. In this article, we address this research gap by calculating and analyzing GHG emissions related to agriculture in Austria from 1830 to 2018. We calculate territorial emissions on an annual basis and include all GHG emissions from the processes directly involved in agricultural production. Based on this time series, we quantify the relative importance of major drivers of changes in GHG emissions across time and agricultural product categories, applying a structural decomposition analysis. We find that agricultural GHG emissions in Austria increased by 69 % over the total study period, from 4.6 Mt. CO2e/yr in 1830 to 7.7 Mt. CO2e/yr in 2018. While emissions increased only moderately from 1830 to 1945 (+22 % overall), with strong fluctuations between 1914 and 1945, they doubled from 1945 to 1985. In the most recent period from 1985 to 2018, emissions fell by one third, with decreases leveling off over time. Our decomposition analysis reveals that increases in agricultural production per capita most importantly contributed to the high growth in GHG emissions from 1945 to 1985. Conversely, decreasing emission intensities of products and a more climate friendly product mix were key drivers in the emissions reduction observed after 1985. We also contribute to the discussion around the global warming potential star (GWP*), by calculating GHG emissions based on this alternative metric, and contextualize our data within total socio-economic GHG emission trends. By providing insights into the historical trends and drivers of agricultural GHG emissions, our findings enhance the understanding of their long-term historical dynamics and adds to the knowledge base for future mitigation efforts.
Feeding 9–10 billion people by 2050 and preventing dangerous climate change are two of the greatest challenges facing humanity. Both challenges must be met while reducing the impact of land ...management on ecosystem services that deliver vital goods and services, and support human health and well‐being. Few studies to date have considered the interactions between these challenges. In this study we briefly outline the challenges, review the supply‐ and demand‐side climate mitigation potential available in the Agriculture, Forestry and Other Land Use AFOLU sector and options for delivering food security. We briefly outline some of the synergies and trade‐offs afforded by mitigation practices, before presenting an assessment of the mitigation potential possible in the AFOLU sector under possible future scenarios in which demand‐side measures codeliver to aid food security. We conclude that while supply‐side mitigation measures, such as changes in land management, might either enhance or negatively impact food security, demand‐side mitigation measures, such as reduced waste or demand for livestock products, should benefit both food security and greenhouse gas (GHG) mitigation. Demand‐side measures offer a greater potential (1.5–15.6 Gt CO2‐eq. yr−1) in meeting both challenges than do supply‐side measures (1.5–4.3 Gt CO2‐eq. yr−1 at carbon prices between 20 and 100 US$ tCO2‐eq. yr−1), but given the enormity of challenges, all options need to be considered. Supply‐side measures should be implemented immediately, focussing on those that allow the production of more agricultural product per unit of input. For demand‐side measures, given the difficulties in their implementation and lag in their effectiveness, policy should be introduced quickly, and should aim to codeliver to other policy agenda, such as improving environmental quality or improving dietary health. These problems facing humanity in the 21st Century are extremely challenging, and policy that addresses multiple objectives is required now more than ever.
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