Embodied HANPP of feed and animal products: Tracing pressure on ecosystems along trilateral livestock supply chains 1986-2013.

The global livestock system puts increasing pressures on ecosystems. Studies analyzing the ecological impacts of livestock supply chains often explain this pressure by the increasing demand for animal products. Food regime theory proposes a more nuanced perspective: it explains livestock-related pressures on ecosystems by systemic changes along the supply chains of feed and animal products, notably the liberalization of agricultural trade. This study proposes a framework supporting empirical analyses of such claims by differentiating several steps of livestock supply chains. We reconstructed "trilateral" livestock supply chains linking feed production, livestock farming, and final consumption, based on the global flows of 161 feed and 13 animal products between 222 countries from 1986 to 2013. We used the embodied Human Appropriation of Net Primary Production (eHANPP) indicator to quantify pressures on ecosystems linked to these trilateral livestock supply chains. We find that livestock induced 65 % of agriculture's pressure on ecosystems, mostly through cattle grazing. Between 1986 and 2013, the fraction of livestock-related eHANPP that was traded internationally doubled from 7.1 % to 15.6 %. eHANPP related to the trade of feed was mostly linked to soybean imported for pig meat production, whereas eHANPP associated to traded animal products was mostly linked to cattle meat. eHANPP of traded animal products was lower but increased faster than eHANPP of feed trade. eHANPP was highest at the feed production level in South and North America, and at the consumption level in Eastern Asia. In Northern Asia and Eastern Europe, eHANPP was lowest at the animal products production level. In Western Europe, the eHANPP was equal at the animal products production and consumption levels. Our findings suggest that options to reduce livestock's pressures on ecosystems exist at all levels of the supply chain, especially by reducing the production and consumption in high-consuming countries and regulating international supply chains.

Altered growth conditions more than reforestation counteracted forest biomass carbon emissions 1990-2020.

Understanding the carbon (C) balance in global forest is key for climate-change mitigation. However, land use and environmental drivers affecting global forest C fluxes remain poorly quantified. Here we show, following a counterfactual modelling approach based on global Forest Resource Assessments, that in 1990-2020 deforestation is the main driver of forest C emissions, partly counteracted by increased forest growth rates under altered conditions: In the hypothetical absence of changes in forest (i) area, (ii) harvest or (iii) burnt area, global forest biomass would reverse from an actual cumulative net C source of c. 0.74 GtC to a net C sink of 26.9, 4.9 and 0.63 GtC, respectively. In contrast, (iv) without growth rate changes, cumulative emissions would be 7.4 GtC, i.e., 10 times higher. Because this sink function may be discontinued in the future due to climate-change, ending deforestation and lowering wood harvest emerge here as key climate-change mitigation strategies.

Quantifying and attributing land use-induced carbon emissions to biomass consumption: A critical assessment of existing approaches.

Biomass production generates land use impacts in the form of emissions from Forestry and Other Land Use (FOLU), i.e. due to changes in ecosystem carbon stocks. Recently, consumption-based accounting (CBA) approaches have emerged as alternatives to conventional production-based accounts, quantifying FOLU emissions associated with biomass consumption, for example, of particular territories. However, the quantification and allocation of FOLU emissions to individual biomass products, a fundamental part of CBA approaches, is a complex endeavour. Existing studies make diverging methodological choices, which are rarely critically discussed. In this study, we provide a structured overview of existing CBA approaches to estimating FOLU emissions. We cluster the literature in a two-by-two grid, distinguishing the primary element under investigation (impacts of changing consumption patterns in a region vs. impacts of consumption on production landscapes) and the analytical lens (prospective vs retrospective). Further, we identify three distinct dimensions which characterise the way in which different studies allocate FOLU emissions to biomass products: the choice of reference system and the spatial and temporal scales. Finally, we identify three frontiers that require future attention: (1) overcoming structural biases which underestimate FOLU emissions from territories that experienced deforestation in the distant past, (2) explicitly tackling the interdependence of proximate causes and ultimate drivers of land use change, and (3) assessing uncertainties and understanding the effects of land management. In this way, we enable a critical assessment of appropriate methods, support a nuanced interpretation of results from particular approaches as well as enhance the informative value of CBA approaches related to FOLU emissions. Our analysis contributes to discussions on sustainable land use practices with respect to biomass consumption and has implications for informing international climate policy in scenarios where consumption-based approaches are adopted in practice.

Modeling and empirical validation of long-term carbon sequestration in forests (France, 1850-2015).

The development of appropriate tools to quantify long-term carbon (C) budgets following forest transitions, that is, shifts from deforestation to afforestation, and to identify their drivers are key issues for forging sustainable land-based climate-change mitigation strategies. Here, we develop a new modeling approach, CRAFT (CaRbon Accumulation in ForesTs) based on widely available input data to study the C dynamics in French forests at the regional scale from 1850 to 2015. The model is composed of two interconnected modules which integrate biomass stocks and flows (Module 1) with litter and soil organic C (Module 2) and build upon previously established coupled climate-vegetation models. Our model allows to develop a comprehensive understanding of forest C dynamics by systematically depicting the integrated impact of environmental changes and land use. Model outputs were compared to empirical data of C stocks in forest biomass and soils, available for recent decades from inventories, and to a long-term simulation using a bookkeeping model. The CRAFT model reliably simulates the C dynamics during France's forest transition and reproduces C-fluxes and stocks reported in the forest and soil inventories, in contrast to a widely used bookkeeping model which strictly only depicts C-fluxes due to wood extraction. Model results show that like in several other industrialized countries, a sharp increase in forest biomass and SOC stocks resulted from forest area expansion and, especially after 1960, from tree growth resulting in vegetation thickening (on average 7.8 Mt C/year over the whole period). The difference between the bookkeeping model, 0.3 Mt C/year in 1850 and 21 Mt C/year in 2015, can be attributed to environmental and land management changes. The CRAFT model opens new grounds for better quantifying long-term forest C dynamics and investigating the relative effects of land use, land management, and environmental change.