Global food systems contribute to climate change, the transgression of planetary boundaries and deforestation. An improved understanding of the environmental impacts of different food system futures ...is crucial for forging strategies to sustainably nourish a growing world population. We here quantify the greenhouse gas (GHG) emissions of global food system scenarios within a biophysically feasible “option space” in 2050 comprising all scenarios in which biomass supply – calculated as function of agricultural area and yields – is sufficient to cover biomass demand – derived from human diets and the feed demand of livestock. We assessed the biophysical feasibility of 520 scenarios in a hypothetical no-deforestation world.
For all feasible scenarios, we calculate (in) direct GHG emissions related to agriculture. We also include (possibly negative) GHG emissions from land-use change, including changes in soil organic carbon (SOC) and carbon sinks from vegetation regrowth on land spared from food production. We identify 313 of 520 scenarios as feasible. Agricultural GHG emissions (excluding land use change) of feasible scenarios range from 1.7 to 12.5 Gt CO2e yr−1. When including changes in SOC and vegetation regrowth on spare land, the range is between −10.7 and 12.5 Gt CO2e yr−1. Our results show that diets are the main determinant of GHG emissions, with highest GHG emissions found for scenarios including high meat demand, especially if focused on ruminant meat and milk, and lowest emissions for scenarios with vegan diets. Contrary to frequent claims, our results indicate that diets and the composition and quantity of livestock feed, not crop yields, are the strongest determinants of GHG emissions from food-systems when existing forests are to be protected.
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•We present an option space of 313 global food-system scenarios in 2050.•The scenarios were feasible without deforestation.•The net greenhouse gas emissions range from −10.7 to 12.5 Gt CO2e/yr.•Freed-up land that is left to regrowth shows huge carbon-sink potentials.•Crucial are diets and livestock feed-intake, but not crop-yield gains to cut GHGs.
In recent years, the strategic role certain metals play is seen as central to the geopolitics promulgated by state agents in the North. While a switch to renewable energy and an increase in energy ...efficiency might be instrumental to reducing dependence on fossil energy, it increases dependence on metals. This paper starts from an analysis of the likely availability of metals in the near future and then proceeds to investigate political concerns raised by considering the geological fundamentals of social development at the peripheries of the capitalist world‐system. The inequality of metal stocks, future metal requirements and the ensuing political challenges are investigated, taking copper as an example. The final section is dedicated to the discussion of regulatory challenges in view of multiple constraints on metal extraction. This section also highlights the preconditions of a socially legitimate transition to a renewable energy system in the coming period of socio‐ecological transformation.
Human use of biomass has become a major component of the global biogeochemical cycles of carbon and nitrogen. The use of land for biomass production (e.g. cropland) is among the most important ...pressures on biodiversity. At the same time, biomass is indispensable for humans as food, animal feed, raw material and energy source. In order to support research into these complex issues, we here present a comprehensive assessment of global socioeconomic biomass harvest, use and trade for the year 2000. We developed country-level livestock balances and a consistent set of factors to estimate flows of used biomass not covered by international statistics (e.g. grazed biomass, crop residues) and indirect flows (i.e. biomass destroyed during harvest but not used). We found that current global terrestrial biomass appropriation amounted to 18.7 billion tonnes dry matter per year (Pg/yr) or 16% of global terrestrial NPP of which 6.6 Pg/yr were indirect flows. Only 12% of the economically used plant biomass (12.1 Pg/yr) directly served as human food, while 58% were used as feed for livestock, 20% as raw material and 10% as fuelwood. There are considerable regional variations in biomass supply and use. Distinguishing 11 world regions, we found that extraction of used biomass ranged from 0.3 to 2.8 t/ha/yr, per-capita values varied between 1.2 and 11.7 t/cap/yr (dry matter). Aggregate global biomass trade amounted to 7.5% of all extracted biomass. An analysis of these regional patterns revealed that the level of biomass use per capita is determined by historically evolved patterns of land use and population density rather than by affluence or economic development status. Regions with low population density have the highest level of per-capita biomass use, high-density regions the lowest. Livestock, consuming 30–75% of all harvested biomass, is another important factor explaining regional variations in biomass use. Global biomass demand is expected to grow during the next decades; the article discusses some options and possible limitations related to such a scenario.
There is a growing recognition that the interrelations between agriculture, food, bioenergy, and climate change have to be better understood in order to derive more realistic estimates of future ...bioenergy potentials. This article estimates global bioenergy potentials in the year 2050, following a “food first” approach. It presents integrated food, livestock, agriculture, and bioenergy scenarios for the year 2050 based on a consistent representation of FAO projections of future agricultural development in a global biomass balance model. The model discerns 11 regions, 10 crop aggregates, 2 livestock aggregates, and 10 food aggregates. It incorporates detailed accounts of land use, global net primary production (NPP) and its human appropriation as well as socioeconomic biomass flow balances for the year 2000 that are modified according to a set of scenario assumptions to derive the biomass potential for 2050. We calculate the amount of biomass required to feed humans and livestock, considering losses between biomass supply and provision of final products. Based on this biomass balance as well as on global land-use data, we evaluate the potential to grow bioenergy crops and estimate the residue potentials from cropland (forestry is outside the scope of this study). We assess the sensitivity of the biomass potential to assumptions on diets, agricultural yields, cropland expansion and climate change. We use the dynamic global vegetation model LPJmL to evaluate possible impacts of changes in temperature, precipitation, and elevated CO2 on agricultural yields. We find that the gross (primary) bioenergy potential ranges from 64 to 161 EJ y−1, depending on climate impact, yields and diet, while the dependency on cropland expansion is weak. We conclude that food requirements for a growing world population, in particular feed required for livestock, strongly influence bioenergy potentials, and that integrated approaches are needed to optimize food and bioenergy supply.
► We analyze the sensitivity of bioenergy potentials to diets, yields and climate change. ► Global bioenergy potentials in 2050 excluding forestry are 64-161 EJ y-1. ► Food and livestock feed requirements strongly influence bioenergy potentials. ► Food crop yields affect the area available for energy crops. ► Climate-change impacts on bioenergy potentials may be substantial but are highly uncertain.
•We present the diagnostic biophysical land-system and GHG emission model BioBaM-GHG 2.0.•BioBaM is designed for evaluating the feasibility and associated GHG emissions of large numbers of agro-food ...system and land-use scenarios at various scales.•We present model algorithms, data structures and the software environment.•As illustrative example, we analyse scenarios for the expansion of agro-ecological measures in the European Union.•As second example, we present an assessment of global potentials for afforestation as climate mitigation measure.
Close to 40% of Earth's land area is used for agriculture to provide humankind with plant- and animal-based food, fibers or bioenergy. Future trends in agricultural land use, livestock husbandry and associated environmental pressures are determined by developments in the food sector, agricultural productivity, technology, and many other influencing factors. Scenario analysis helps to understand their complex interaction and obtain quantitative insight. We here present an in-depth description of the agricultural land use model BioBaM-GHG 2.0 (“BioBaM”), designed for evaluating large numbers of agricultural and livestock production scenarios assembled on the basis of exogenous assumptions on food systems, crop yields and other factors. BioBaM determines the feasibility of specific parameter combinations and the corresponding greenhouse gas (GHG) emissions from agricultural activities, livestock husbandry, land-use change and other activities. We provide a description of the software environment, the model's data structures, input and output variables and model algorithms. To illustrate the model's capabilities and the scope of model applications, we describe two exemplary studies performed with BioBaM: We assess implications of agro-ecological innovations and the feasibility of their widespread application in order to illustrate their implications in terms of agricultural self-sufficiency and GHG emissions. This first case study aligns a small number of individual scenarios with qualitative storylines. We also showcase a ”biophysical option space approach”, which represents a comprehensive sensitivity analysis regarding the multidimensional uncertainties inherent to main influencing parameters, i.e. projections for diets and yields; assumptions on cropland use for bioenergy, and regarding grassland intensification. The global potential of forest regeneration for climate change mitigation serves as an example for this second approach. The option space comprises 90 scenarios and encompasses the full range of literature estimates on GHG mitigation from afforestation in 2050 (0.5 – 7 Gt CO2/yr). It further shows that the potential is zero under certain diet-yield-combinations. Assuming zero energy crop cultivation and global convergence to a healthy reference diet, the sequestration potential of afforestation rises to 10 Gt CO2/yr in 2050. These exemplary applications illustrate how option spaces developed with BioBaM can complement scenario-based assessments that usually focus on small numbers of individual scenarios: Option spaces shift attention to a wider scope of conceivable futures and thus support a comprehensive view on systemic relations and dependencies, whereas analyses with few scenarios allow apprehension of much more detailed scenario narratives and qualifications.
Achieving a global forest transition, that is a shift from deforestation to reforestation, is important for climate-change mitigation. Forest transitions are enabled by socioecological processes, ...including land displacement, agricultural intensification and woodfuel substitution for other energy, but their respective contributions remain poorly understood. Here, by means of a scenario approach we quantify the importance of enabling conditions of the forest transition in Austria between 1830 and 1910 and their overall emissions implications, including the forest carbon sink potential in the hypothetical absence of wood use. We combine historical databases on land use, biomass production and energy use and an empirical dynamic forest growth model to develop five hypothetical counterfactual scenarios. The scenarios assume food and energy consumption in the absence of woodfuel substitution, food imports and three variations of agricultural intensification and assess effects on forest change and carbon balances. We find that the absence of any of the enabling conditions would have completely depleted forest biomass by 1910. Livestock efficiency gains and woodfuel substitution, two rarely discussed drivers of forest change, were equally important as yield increase and land displacement. The cumulative forest sink potential in the absence of any wood extraction throughout the period was found to be about twice the forest carbon stock in 1830. All counterfactual scenarios led to increasing overall emissions, “no woodfuel substitution” being closest to the historical trend. Our work lays the ground for a new typology of forest transitions according to the socioecological processes that enable them.
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•How did changes in energy and biomass use enable the Austrian forest transition?•We quantify forest change and emissions in 5 counterfactual scenarios for 1830–1910.•Suppressing any enabling factor resulted in forest depletion and more emissions.•Livestock and energy change were equally important as imports and yield increase.•Forest change is embedded in socio-ecological dynamics relevant for mitigation.
Sedentary extensive small ruminant farming systems are highly important for the preservation of High Nature Value (HNV) farmland. Both the abandonment of grazing and overgrazing have led to ...environmental degradation in many Mediterranean regions. On the Greek island of Samothrace, decades of overgrazing by sheep and goats has caused severe degradation of local ecosystems. The present study highlights the importance of regional contexts for national and EU agricultural policies in regard to sustainable development of sedentary extensive livestock systems. By utilizing the conceptual framework of socio-ecological systems research, we analyze the interdependencies of environmental, economic and social factors on a local island level. Results show that between 1929 and 2016, the livestock and land-use system of Samothrace transformed from a diverse system towards a simplified system, solely used for small ruminant production. Total livestock units increased from 2200 in 1929 to 7850 in 2002, declining to 5100 thereafter. The metabolic analysis conducted for the years 1993–2016 shows that 80–90% of the feed demand of small ruminants was covered by grazing, exceeding available grazing resources for at least a decade. The regional implementation of CAP (Common Agricultural Policy) continues to support excessively high animal numbers, while farmers are highly dependent on subsidies and find themselves in an economic deadlock.
Wood biomass forms the basis for a variety of products and it represents an important source of technical energy. Woodfuels and forests play an important role for climate change mitigation, by their ...ability to replace fossil fuel and sequester atmospheric carbon. At the same time, wood extraction is an important driver for deforestation. However, large uncertainties relate to the amount and spatio-temporal pattern of wood use. We here present a comprehensive assessment of wood biomass flows in 11 world regions from 1990 to 2010. We found that global total biomass appropriation (TBA) amounts to 1.81GtC/year in 1990 and 1.94GtC/year in 2010 (+7%). In 2010, TBA represents 4% of the global forest net primary production. Only 54% of TBA enters socioeconomic systems while 46% remain in forests or represent waste flows. About 56% of economically used wood biomass enters the energy sector. There are considerable regional variations in wood biomass flows among world regions, owing to differences in population, affluence, and area. Global demand for wood is expected to increase in the near future, putting additional pressure to forest ecosystems. We discuss the potential of cascading use of wood as a means to reduce impacts related to resource use.
•We present a comprehensive assessment of wood biomass flows in 11 world regions.•We discuss the potential for cascading use of wood as a means to reduce impacts.•There are significant uncertainties on global used extraction of wood.•There is a massive regional variation in the patterns of wood biomass flows.•In the last 20years, the trends of global wood used extraction remains stable.
•Science and policy usually neglect that forest transitions have hidden emissions.•These may stem from agricultural intensification, woodfuel substitution or land displacement.•Combined with full GHG ...accounts and politics, they inform effective and just mitigation policy.
Achieving a global forest transition, that is, a shift from net deforestation to reforestation, is essential for climate change mitigation. However, both land-based climate change mitigation policy and research on forest transitions neglect key processes that relieve pressure from forests, but cause emissions elsewhere (‘hidden emissions’). Here, we identify three major causes of hidden emissions of forest transitions, that is, emissions from agricultural intensification, from woodfuel substitution, and from land displacement. Taken together, these emissions may compromise the climate change mitigation effect of national forest transitions. We propose to link analyses of hidden emissions of forest transitions with quantifications of full socio-ecological greenhouse-gas accounts and analyses of their politics. Such an integration allows for drawing lessons for effective and just climate change mitigation policies.
Wildfires and land use play a central role in the long‐term carbon (C) dynamics of forested ecosystems of the United States. Understanding their linkages with changes in biomass, resource use, and ...consumption in the context of climate change mitigation is crucial. We reconstruct a long‐term C balance of forests in the contiguous U.S. using historical reports, satellite data, and other sources at multiple scales (national scale 1926–2017, regional level 1941–2017) to disentangle the drivers of biomass C stock change. The balance includes removals of forest biomass by fire, by extraction of woody biomass, by forest grazing, and by biomass stock change, their sum representing the net ecosystem productivity (NEP). Nationally, the total forest NEP increased for most of the 20th century, while fire, harvest and grazing reduced total forest stocks on average by 14%, 51%, and 6%, respectively, resulting in a net increase in C stock density of nearly 40%. Recovery from past land‐use, plus reductions in wildfires and forest grazing coincide with consistent forest regrowth in the eastern U.S. but associated C stock increases were offset by increased wood harvest. C stock changes across the western U.S. fluctuated, with fire, harvest, and other disturbances (e.g., insects, droughts) reducing stocks on average by 14%, 81%, and 7%, respectively, resulting in a net growth in C stock density of 14%. Although wildfire activities increased in recent decades, harvest was the key driver in the forest C balance in all regions for most of the observed timeframe.
Plain Language Summary
We estimate past forest fires in four regions of the contiguous United States from 1926 to 2017 using historical statistics and satellite data. We compare the biomass removed from forests by wildfires, wood harvest, and forest grazing to identify which of these indicators had the strongest impact on forest biomass. Fire suppression and biomass recovery from past harvest in the twentieth century led to biomass regrowth. Forest regrowth was stronger in the East of the United States than in the West. Recently, wildfires have increased in the West. Higher tree mortality, drought, windthrow, and insects counteracted forest growth in the West. We conclude that fire suppression contributed to forest regrowth in the past, but harvest had the strongest impact in all regions. We show that the connection between wildfires, harvest, and grazing is an important factor for biomass change in forests and needs to be investigated over long time periods.
Key Points
We present a new data set, reconstructing biomass removals by fire, harvest, and grazing in U.S. forests on a regional scale from 1941 to 2017
Harvest and fire were the most intensive removals of biomass over the 20th century. Regional trends diverge from national trends
In the context of natural climate solutions, long‐term and regional dynamics of interconnected drivers of forest biomass change need to be considered
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