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

Abstract

Abstract There is increasing recognition of the tension between livestock production and freshwater availability. Changes in freshwater availability can be generated by both freshwater consumptive and freshwater degradative use. Agriculture is a major water user, and beef cattle and sheep farming is an important agricultural activity in New Zealand (NZ). This study assessed potential environmental impacts associated with water use in beef cattle and sheep farming in NZ, following a water footprint method compliant with life cycle assessment principles with a focus on the water scarcity footprint and eutrophication potential (EP) impacts. The life cycle required for the production of beef cattle and sheep was analysed cradle-to-farm-gate, excluding animal transport or processing. Survey data from Beef and Lamb New Zealand for the year 2009/10 were used to cover a range of beef cattle and sheep farm types throughout NZ (426 farms averaged in seven farm classes), and water scarcity footprint and EP weighted averages were calculated for beef cattle and sheep. The normalised NZ weighted average water scarcity footprint of beef cattle of 0.37 L H2O-eq/kg LW was lower than the published normalised values for the water scarcity footprint of beef cattle produced in Australia (3.3–221 L H2O-eq/kg LW) and in the UK. Also, the NZ weighted average water scarcity footprint of sheep of 0.26 L H2O-eq/kg meat (assuming that 40% LW was converted into meat) was lower than the water scarcity footprint of sheep meat reported for the UK (8.4–23.1 L H2O/kg meat). 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.