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Agri-food systems (AFS) and their value chains are currently under pressure to minimize environmental degradation and secure a more sustainable future. Sustainability transitions are needed to shift from well-established, yet vulnerable systems to more sustainable systems. Agent-based modeling (ABM) as a method to study complex systems is now widely used in transition modeling. We performed a systematic review to analyze the potential of ABM to yield insights into sustainability transitions in AFS. Specifically, we investigated the understanding that agent-based models can support better understanding of sustainability transitions in AFS. We identified potential in participatory modeling methods as well as combining agent-based models with complementary methods. The assessment of the sustainability dimensions was quite balanced between economic and environmental dimensions, but the social dimension was underrepresented. Here, we identify the main features to further advance ABM of sustainability transitions in AFS.

In recent sustainability assessments, transdisciplinary approaches have been used to bridge contested normative views among many societal actors, policymakers and researchers. Transdisciplinary research is mainly based on three premises: (1) various perspectives need to be incorporated and discussed to empower actors, (2) the collaboration and co-creation of knowledge between academic and societal actors allows to better grasp the complexity of a real-world problem, and (3) a mutual learning process arises which could increase the legitimacy of decisions and their implementation in practice. Despite many examples of transdisciplinary projects, few assessments have been done that question whether such a project fulfils the premises of transdisciplinary research. Therefore, we report on a reflexive assessment of an initiative set up to foster the transformation of the Flemish agri-food system towards sustainability. The case study involved both scientific and societal actors with different views, making it possible to implement a transdisciplinary process, evaluate the expectations and give suggestions for future processes. Evaluation criteria are linked to context, process and outcomes. Analysis of the qualitative and quantitative data indicates that the initiative did empower the transformation towards sustainability. Furthermore, results show that, in this case, a transdisciplinary approach can fulfil its premises. However, some critical factors are identified, such as the importance of the context specificity and a flexible, adaptive and iterative process.

AbstractLengthening of the growing season at high latitudes, observed by satellites with the Normalized Difference Vegetation Index (NDVI), has been ascribed to climate warming. To test this assumption, and to verify whether changes in vegetation greenness are quantitative or qualitative, we experimentally warmed patches of High Arctic tundra with infrared heating in Northeast Greenland. By analyzing digital images of the vegetation, changes in cover were distinguished from changes in senescence. During the season, experimental warming significantly increased green cover, for example, at the time of peak cover, the total green cover was enhanced from 59.1 to 67.3%. The dominant wavelength (hue) reflected by our tundra plots shifted from yellow-green to yellow. Experimental warming with 2.5°C delayed this hue-shift by 15 d. The results demonstrate that higher summer temperatures do not only promote plant growth at these latitudes but also retard and/or postpone the senescence process, contrary to indications from previous research that late-season phenology in the High Arctic is governed by photoperiod.

AbstractTundra ecosystems constitute large stocks of carbon and might therefore, if climate warming releases CO2, induce positive feedback and amplify temperature increase. We studied the effect of a 2.5°C temperature increment, induced by controlled infrared irradiation, on various components of the carbon balance of a High Arctic tundra ecosystem at Zackenberg in Northeast Greenland (74°N, 21°W) over the 1999 growing season. Gross photosynthesis (Pgross), belowground respiration (Rsoil), and canopy respiration (Rcanopy) were regularly determined with closed dynamic CO2exchange systems, and the whole-growing season C-balance was reconstructed by relating these components to potentially controlling factors (green cover, soil moisture, radiation, soil and canopy temperature, and thawing depth). Thawing depth and green cover increased in heated plots, while soil moisture was not significantly affected. Pgrossincreased 24.2%, owing to both a green cover and a physiological influence of warming. Belowground respiration was enhanced 33.3%, mainly through direct warming impact and in spite of lower Q10in the heated plots; the factors controlling Rsoilwere day of the year and soil moisture. Rcanopydid not differ significantly between treatments, although green cover was higher in the heated plots. This tundra ecosystem acted as a relatively small net sink both under current (0.86 mol CO2m−2) and heated (1.24 mol CO2m−2) conditions. Nevertheless, turnover increased, which was best explained by a combination of direct and indirect temperature effects, and delayed senescence.