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Hidden Emissions of Forest Transitions: GHG effects of socio-metabolic processes reducing pressures on forests

Periodic Reporting for period 3 - HEFT (Hidden Emissions of Forest Transitions: GHG effects of socio-metabolic processes reducingpressures on forests)

Reporting period: 2021-04-01 to 2022-09-30

Forests are major carbon pools, thus forest expansion and thickening are expected to contribute significantly to mitigating global climate change. In the past, national-scale forest transitions, i.e. shifts from net deforestation to reforestation, have generally occurred in contexts of industrialization, coinciding with significant changes in resource use. Processes enabling forest transitions but causing additional emissions may impede the climate change mitigation effect of reforestation. However, the systemic links between forest transitions, their underlying socio-metabolic processes and associated greenhouse gas (GHG) emissions have been neither systematically explored nor quantified.
HEFT introduces the idea of “hidden emissions of forest transitions”, i.e. the GHG emissions from processes that reduce pressure on forests and enable reforestation. Hidden emissions may stem from processes such as substitution of fuelwood by modern energy sources, intensification of agriculture, and land displacement. Adopting an interdisciplinary socio-ecological perspective, HEFT quantifies the sinks of forest transitions and contrasts them with the socio-metabolic emissions resulting from processes enabling them.
Forest transitions are analyzed at local, national and supranational scales: in Europe since c. 1850, in North America since c. 1880, and in Southeast Asia since 1980. A global-scale assessment complements the regional case studies. We integrate sources and analytical methods from environmental and social sciences as well as the humanities to analyze context-specific trajectories and general interlinkages of forest transitions and resource use in various socio-political contexts, and understand their GHG implication. The sound understanding of the links between forest change and resource use is used to identify the least GHG-intensive trajectories and to draw lessons for land-based climate-change mitigation policies that are both physically effective and socio-politically viable.
Firstly, the project has laid the conceptual and methodological grounds to investigate hidden emissions of forest transitions. Conceptual publications highlight novel ways forward to address the links between forest transitions and different types of resource use to quantify their hidden emissions and inform ecologically sustainable and socially just forest recovery processes. At the methodological level, advances have been made to quantify the long-term carbon sinks in forest transitions in relation to changes in resource use. We developed the CRAFT model that simulates forest carbon stock change, relying on a time- and space-specific function of net primary production (NPP) and biomass stocks in forests. Going beyond existing models, CRAFT simulates the effect of biomass extraction on biomass stock change, while enabling to detect changes in tree growth conditions. This model can now be used in combination with empirical work on long-term changes in agriculture, biomass trade, and energy use, to develop counterfactual scenarios, quantifying the effects on forest carbon change of individual forest relief processes.
Secondly, HEFT has compiled a large body of empirical evidence for analyzing forest transitions, changes in resource use and associated GHG fluxes in local, national and regional case studies as well as at the global scale. Data sources include historical and recent statistics on forest and agricultural change from databases, publications and archives. In addition, qualitative information on the socio-political context of forest transitions has been collected in systematic literature queries and through expert interviews. We have empirically investigated local and national case studies in Europe from the 19th through 21st centuries, Southeast Asia, late 20th century to present, and North America, late 19th century to present.
Thirdly, major quantitative and qualitative efforts are under way to analyze trajectories of forest transitions and their connections to resource use and socio-political dynamics which are already yielding important insights. We identified the reduction of agricultural practices in forests (e.g. forest grazing in temperate regions and shifting cultivation in the tropics) as important factor accompanying forest transitions. Combining quantitative methods of environmental accounting with qualitative methods from political ecology and environmental history, we investigate similarities and differences of these processes across case studies, focusing on both their biophysical and their socio-political dimensions. In addition, counterfactual scenario approaches are applied as a means of analysis to quantitatively assess and compare the relative contributions of changes in specific trends of resource use to forest change, as well as their emissions impacts. We are also working towards coarse typologies to systematically describe forest transitions according to their major biophysical drivers.
Fourthly, we are starting to identify climate-change mitigation potentials of forest transitions based on our findings. In particular, we explore potentials of agroforestry to integrate the aims of biomass provision and carbon sequestration, focusing on Southeast Asia and Europe. In addition, we investigate the option space of biomass provision under specific assumptions of forest conservation and emissions.
Progress beyond the state of the art has been made in the following areas:
• Conceptual introduction of the idea “hidden emissions of forest transitions”, linking forest change to changes in societal resource use and addressing the GHG effect of forest relief processes
• Quantitative assessments of long-term changes (up to 170 years) in forest C stocks in biomass and soils in several national and subnational case studies (United States, France, Austria, Lao PDR)
• Model development to dynamically quantify forest C stocks based on information on area and harvest, applying a time and space-specific relationship of biomass stocks and NPP (CRAFT model)
• Identification of land sparing as a major element of forest transitions across case studies, and analysis of the socio-political dimensions of this process
Expected results until the end of the project
• Identification of forest transitions trajectories according to their major biophysical drivers in global and cross-country comparisons
• Information on the specific links of forest relief processes and forest change in a number of national and regional case studies
• Quantification of the GHG impact of forest relief processes across case studies in North America, Europe, Southeast Asia and at the global scale
• Analyses of changes in fire regimes for selected case studies
• A global assessment of biomass C stocks from 1950 to present
• Reflexion on forest definitions adopted in historical forest inventories and their impact on quantitative assessments of forest change
• Analysis of the interrelation of tree cover and C stocks in the tropics
• Comparative analyses of socio-political contexts of forest transitions
• Assessment of the impact of international trade on forest change
• Investigation of the option space for biomass provision under constrained forest change and GHG emissions
• Exploration of least GHG-intensive forest transitions pathways
Biomass C density in global production forests, according to FRA