Mitigating ecosystem service tradeoffs in rangelands by using grazing duration and timing to manage water quality

1. Mitigating ecosystem service (ES) tradeoffs 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 tradeoffs, and therefore
do not provide options that can alleviate conflict. 2. In semi-arid
rangelands, we examined the potential for managers to mitigate tradeoffs
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 modeled how grazing duration and timing affected
the ability to meet regulatory benchmarks for water quality throughout a
grazing season. 3. 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. 4. 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. 5. Our results suggest that reducing the grazing
duration and shifting its timing are complementary strategies that can
mitigate the tradeoffs between livestock grazing and water quality without
fencing-off riparian areas or removing cattle from pastures with streams.
6. Synthesis and applications. In this study, we found grazing duration
and timing can be used as tools to mitigate ES tradeoffs 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.