Global consequences of afforestation and bioenergy cultivation on ecosystem service indicators

Abstract

Abstract. Land management for carbon storage is discussed as being indispensable for climate change mitigation because of its large potential to remove carbon dioxide from the atmosphere, and to avoid further emissions from deforestation. However, the acceptance and feasibility of land-based mitigation projects depends on potential side effects on other important ecosystem functions and their services. Here, we use projections of future land use and land cover for different land-based mitigation options from two land-use models (IMAGE and MAgPIE) and evaluate their effects with a global dynamic vegetation model (LPJ-GUESS). In the landuse models, carbon removal was achieved either via growth of bioenergy crops combined with carbon capture and storage, via avoided deforestation and afforestation, or via a combination of both. We compare these scenarios to a reference scenario without land-based mitigation and analyse the LPJ-GUESS simulations with the aim of assessing synergies and trade-offs across a range of ecosystem service indicators: carbon storage, surface albedo, evapotranspiration, water runoff, crop production, nitrogen loss, and emissions of biogenic volatile organic compounds.In our mitigation simulations cumulative carbon storage by year 2099 ranged between 55 and 89 GtC. Other ecosystem service indicators were influenced heterogeneously both positively and negatively, with large variability across regions and land-use scenarios. Avoided deforestation and afforestation led to an increase in evapotranspiration and enhanced emissions of biogenic volatile organic compounds, and to a decrease in albedo, runoff, and nitrogen loss. Crop production could also decrease in the afforestation scenarios as a result of reduced crop area, especially for MAgPIE land-use patterns, if assumed increases in crop yields cannot be realized. Bioenergy-based climate change mitigation was projected to affect less area globally than in the forest expansion scenarios, and resulted in less pronounced changes in most ecosystem service indicators than forest-based mitigation, but included a possible decrease in nitrogen loss, crop production, and biogenic volatile organic compounds emissions.

Large uncertainty in carbon uptake potential of land‐based climate‐change mitigation efforts

“…In this study, we only address the uncertainty in land‐based mitigation arising from potential C uptake for a prescribed available area. However, the establishment of negative emissions from land management could also be hindered by unacceptable social or ecological side‐effects (Kartha & Dooley, ; Krause et al., ; Smith, Davis, et al., ), biophysical and biogeochemical climate impacts beyond C (Boysen, Lucht, & Gerten, ; Krause et al., ; Smith, Davis, et al., ), irreversible effects of overshooting CO 2 concentrations (Kartha & Dooley, ; Tokarska & Zickfeld, ), or simply because CCS turns out to be technologically infeasible at commercial scale. There is also strong evidence that the timescales for shifts in farming systems to be realized may be of the order of several decades, substantially delaying the onset of negative emissions from BECCS (Alexander, Moran, Rounsevell, & Smith, ; Brown et al., submitted).…”

“…They were derived to match assumed crop yields in the LUMs. A historic hindcast (1901–1969/1901–1994) was calculated based on initial (1970/1995) fertilizer rates from the LUMs and relative changes in the Land‐Use Harmonization data set (http://luh.umd.edu/index.shtml, see also Krause et al., ). The implementation of the LU data into the DGVMs (e.g., mapping to DGVM vegetation types and defining rules by which managed land expands over natural vegetation), land masks, and additional required input variables (e.g., soil characteristics) were left to the responsibility of the individual DGVM groups.…”

“…However, the land demand/availability of these approaches is highly uncertain (Boysen, Lucht, & Gerten, ; Popp et al., ), and their potential to remove significant amounts of C from the atmosphere is regarded as controversial (Fuss et al., ). In addition, conflicts with other LU, associated supply of ecosystem services, and maintenance/enhancement of biodiversity are highly likely (Krause et al., ; Smith, Davis, et al., ; Williamson, ). Considering typical time frames of decades involved in the planning and establishment of climate mitigation projects, the quantification of their uncertainties in terms of achievable CDR is important to inform policy makers about practicality and risks.…”

Impacts of future agricultural change on ecosystem service indicators

“…However, we also see low simulated carbon sequestration under constant land use compared to the models in Nishina et al (2015), even when excluding models that did not simulate nitrogen limitation. Other important differences between the runs in Krause et al (2017) and ours include our use of different climate forcings and associated photosynthesis scaling parameters.…”

“…A substantial body of research has been built up using such models to examine how future land-use change will affect individual ecosystem services such as carbon sequestration (Brovkin et al, 2013;Lawrence et al, 2018), biodiversity (Jantz et al, 2015;Hof et al, 2018;Di Marco et al, 2019), and water availability and flood risk (Davie et al, 2013;Elliott et al, 2014;Asadieh and Krakauer, 2017). Much less work has been undertaken to evaluate 30 the future of a suite of ecosystem services in an integrated way (Krause et al, 2017;Molotoks et al, 2018). However, such analyses provide critically important evidence for balancing the many competing demands on the land system while achieving climate and societal targets such as those laid out in the Paris Agreement and Sustainable Development goals (Eitelberg et al, 2016;Benton et al, 2018;Verhagen et al, 2018).…”