Choice of metrics matters—Future scenarios on milk and beef production in Norway using an LCA approach.

· Climate change, biodiversity, and land use ratio were assessed for future domestic milk and beef production scenarios in Norway. · The choice of GWP metrics and time frame are highly affecting the results. · Traditional GWP 100 metrics favor the HighY scenario with high milk yield. · The GWP* metrics favor the LowY scenario with low milk yield and no suckler cows. · The LowY scenario increased land use efficiency and lowered biodiversity loss. The consumption of dairy and beef products is expected to increase globally in the future, and at the same time, food must be produced in a more sustainable way, including reduced greenhouse gas (GHG) emissions, avoided feed-food competition, and reduced biodiversity loss. The purpose of the study was to a) provide an overall life cycle assessment (LCA) of these impacts for various future milk and beef production systems in Norway and b) determine how the choice of metrics for climate change affects the results. System boundaries were from cradle to farm gate and the temporal boundary was 2017 with future scenarios for 2040. The actual production and consumption in Norway in 2017 was used as a baseline (BL), and the sustainability of future Norwegian domestic production of milk and beef was assessed through three scenarios for 2040: 1) a trend yield scenario (TrendY) based on an expected increase in milk yield following the present trend, 2) a high yield scenario (HighY) with higher increase in the milk yield per cow per year than the trend, and 3) a low yield scenario (LowY) where the milk yield per cow per year was adjusted for covering the domestic demand for beef solely from dual-purpose production and no domestic specialized beef production. The beef production per dual-purpose cow was kept constant and the remaining domestic demand in scenario 1 and 2 were covered by specialized beef production. Climate change was assessed using both a GWP 100 and a GWP* approach. The HighY scenario had the lowest impact on climate change using GWP 100 , but when taking the different behaviors of short- and long-term climate pollutants into account (GWP*), the ranking of the future scenarios changed and favored LowY. The potential biodiversity loss was lower for the LowY scenario because the proportion of concentrates in the dairy cow ration was decreased due to lower milk yield. Similarly, the feed-food competition was lower (land use ratio < 1) for the LowY. The results of our study suggest that the choice of metric for GWP and time frame highly affects the results and conclusions and strategies for climate smart and sustainable livestock production should therefore be made with caution. [Display omitted] [ABSTRACT FROM AUTHOR]