Water footprint of beef cattle and sheep produced in New Zealand: water scarcity and eutrophication impacts

Blue water losses associated with evapotranspiration from irrigated pasture comprised the greatest proportion of the total water scarcity footprint, despite the small areas of farmland irrigated. The weighted average EP of beef cattle was 51.1 g PO4-eq/kg LW, and the weighted average EP of sheep was 26.1 g PO4-eq/kg LW. The NZ weighted average EP for beef cattle was lower than the 105 g PO4-eq/kg LW reported for European Union suckler beef cattle. On-farm nitrate leaching and phosphorus runoff dominated the EP. From an international marketing perspective, beef cattle and sheep produced in NZ have a potential advantage by having low water scarcity footprints compared to some non-NZ pastoral farming systems due to their production efficiencies and low annual water-stress levels. The impact of NZ pastoral farming on freshwater availability can potentially be reduced by practices that decrease water use, increase feed conversion efficiencies, increase the use of non-irrigated feed supplements, and reduce irrigation. The indicator EP was chosen to enable comparisons with non-NZ studies, but gaseous emissions of nitrogen compounds contributed 33-40% of the total, and their contribution to water pollution is uncertain. This study highlighted the need for a harmonised methodology and as well as to consider specific local contextual information when interpreting the absolute and relative implications of EP results, for example by developing NZ-catchment-specific characterisation factors for aquatic eutrophication in future studies.