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In the United States (U.S.) the West is enduring a severe drought unseen since 800 C.E. (Williams et al., 2022), triggering blue water (aquifers and surface water) shortages and a cascade of regulations from diverting water from agriculture (Parks and Moriarty, 2021) to restricting household water use (Becker, 2022). Alarms over water utilization have renewed public concerns over agriculture’s water footprint. With beef requiring 80-260% more water than other meat sources (Mekonnen and Hoekstra, 2010) the expostulation for the consumption of beef by both public and scientific sectors continues to increase. However, over the last 30 years agricultural industries have made significant advances in crop yields, crop irrigation practices, and cattle efficiencies (Capper, 2011; USDA-ERS, 2022). Despite these advances there is a scientific and consumer disconnect between industry advances and beef cattle’s water use. Without this understanding it becomes increasingly difficult to accurately assess how beef production is contributing to water scarcity and how and where the beef industry needs to improve. Although several beef cattle water models exist, their scope is limited to comparing current production practices rather than comparing temporal changes. In 2011, utilizing life cycle inventories for 6 different beef production systems in the U.S., a farm to gate life cycle assessment (LCA) determined beefs’ water intensity to range from 3.3 to 221 L H2O/kg live weight (Ridoutt et al., 2012). In 2019, using the process based Integrated Farm Systems Model, Rotz et al. (2019) determined U.S. beef cattle water intensity to be 2,034 L/ kg hot carcass weight (HCW). The issues with comparing models and determining changes in water use over time was illustrated in Menendez and Tedeschi (2020), where the researchers stated that broad water values used in literature, inconsistent units, and vast regional differences prevent the direct comparison between models. Therefore, in order to compare beef cattle’s water use over time an “apples to apples” methodology is needed. The objective of the present study sought to incorporate the most recent USDA and university extension values on crop yield, crop irrigation, animal performance, and feedlot ration data into the original Beckett and Oltjen model in order to make direct comparisons of beef cattle’s water use and intensity from 1991 to 2019.
The present study was based on the static model designed by Beckett and Oltjen (1993) depicting beef cattle production in the United States constructed in Excel™. All production schemes within the model were represented on an individual U.S. state basis. The water accounted for in the model was limited to blue water (surface and groundwater). Natural participation (green water) that fell on crops or pasture was not included in this model. As in the original Beckett and Oltjen model, individual states were grouped into regions for presentation purposes. To make direct comparisons to Beckett and Oltjen, regions were identical to that of the 1993 model. These regions were originally assembled with expertise from feedlot nutritionists and extension specialist to represent homogenous feeder groupings. Numbers of cattle, crop production, and irrigation data were used from USDA census and survey data. On 1 January 2019, a total of 31.7- million beef cows and 5.8-million replacement heifers were in U.S. breeding herds, and 26- million animals were fed annually. In total, the U.S. beef cattle herd (feedlot and cull cows) produced 7.7-billion kg of boneless beef, an increase of 10% since 1991. The Sensitivity Analysis Model was used to assess the sensitivity of key parameters (i.e., m3 blue water per ton of feed commodities) consistent throughout livestock water footprint publications (Hoekstra and Mekonnen, 2012; Menendez and Tedeschi, 2020). We increased and then decreased the parameter by 10% and noted the overall change in water intensity for beef production. The value of 10% was selected to enable direct comparisons between the current model and the 1993 Beckett and Oltjen model.
From 1991 to 2019 U.S. beef cattle’s blue water intensity decreased by 37.6% from 3,682 L/ kg of beef to 2,275 L/ kg of beef with total water use for the entire beef cattle herd decreasing by 29%. The decrease in blue water was principally due to decreased irrigation water intensity on pasture and crops, the shift to incorporating byproducts and coproducts into feedlot rations, and the changes in cattle size and beef produced per animal. Despite the decrease in water intensity and water use, water will continue to be a concern for beef cattle production, particularly in the west where surface and ground water are rapidly depleting. With the water scarcity issues in the western United States cattle production may be forced to move to areas with greater blue and green water availability. In future work to account for the movement of cattle, water models will need to further account for trans-spatial movement of cattle. In conclusion, although the industry has heavily focused on greenhouse gas mitigation there needs to be continuous attention on water use and water mitigation.
Efficiencies in farming and livestock production are directly linked to both a decrease in water intensity and absolute water use. Despite the decrease in water intensity and water use, water will continue to be a concern for beef cattle production, particularly in the west where surface and ground water are rapidly depleting. With the water scarcity issues in the western United States cattle production may be forced to move to areas with greater blue and green water availability. In future work to account for the movement of cattle, water models will need to further account for trans-spatial movement of cattle. In conclusion, although the industry has heavily focused on greenhouse gas mitigation there needs to be continuous attention on water use and water mitigation.