Rotational grazing can mitigate ecosystem service trade-offs between livestock production and water quality in semi-arid rangelands.
Mitigating ecosystem service (ES) trade-offs is a key management goal in locations where stakeholders value different and potentially conflicting ecosystem services (ESs). However, studies are not often designed to examine how local management actions address ES trade-offs, and therefore do not provide options that can alleviate conflict. In semi-arid rangelands, we examined the potential for managers to mitigate trade-offs between livestock production and water quality. To move away from solutions that offer cattle removal as a singular management strategy, we examined how cattle presence, plus two elements of rotational grazing-the length of time cattle spend on rangeland (i.e. duration), and the season grazed (i.e. timing), affected stream Escherichia coli (E. coli concentrations). We also modelled how grazing duration and timing affected the ability to meet regulatory benchmarks for water quality throughout a grazing season. Grazing duration controlled the length of time E. coli concentrations were high in streams. In short- and medium-duration systems, E. coli concentrations were high for shorter periods of time than in long-duration systems, resulting in fewer violations of national and state water quality standards. Stream E. coli concentrations showed a consistent seasonal pattern, starting low in spring, peaking in summer and declining towards fall. Thus, grazing during spring or fall, rather than in summer, reduced the number of days that E. coli levels exceeded water quality standards. Our results suggest that reducing the grazing duration and shifting its timing are complementary strategies that can mitigate the trade-offs between livestock grazing and water quality without fencing-off riparian areas or removing cattle from pastures with streams. Synthesis and applications. In this study, we found grazing duration and timing can be used as tools to mitigate ecosystem service (ES) trade-offs between cattle production and water quality in rangeland streams. Shorter grazing durations reduced the number of days E. coli levels were above regulatory limits, as did grazing that occurred either early or late in the season. These results support the idea that rotational grazing can be an effective strategy to manage water quality in semi-arid rangelands. They also highlight the need for more grazing studies that incorporate gradients of duration and timing into study designs.