Building Resilience to Reduce Carbon, Nitrogen and Water Footprints of the Dairy Industry.

Milk production is the third largest agricultural industry in the United States, with California, New York, Wisconsin and Idaho being the top four dairy-producing states. Predicted climate change involves a 2°C increase in average temperatures, with variable precipitation and increased frequency of extreme weather. Therefore, it is important that resilience is built into dairy production systems to mitigate and adapt to climate change. We need to identify and adopt sustainable mitigation practices that reduce the overall carbon, nitrogen and water footprints of the dairy industry. These practices should target reducing enteric methane production, improving N use efficiency in cattle, reducing herd size through herd management and improved animal health, reducing ammonia and greenhouse gas emissions from animal housing and manure storage, and enhancing N utilization and decreasing ammonia and greenhouse gas losses from fertilizer and manure applications in feed and forage production. Additionally, as climate change alters the amount and seasonal distribution of water, it will be necessary to have a good understanding of water uses on dairy farms in order to target conservation practices. There is considerable variation among dairies, which is presumably caused by differences in cleaning practices and the amounts of water used for cooling cows, milk and equipment. All mitigation practices need to be evaluated through socioeconomic analyses, and potential barriers to their adoption examined for successful technology transfer. More research is required to provide tools to manage feed, cattle and water on the farm to build system resilience to climate variability and to mitigate climate change via reductions in carbon, nitrogen and water footprints.