Adaptive rangeland management benefits grassland birds utilizing opposing vegetation structure in the shortgrass steppe

Abstract

Rangelands are temporally and spatially complex socioecological systems on which the predominant land use is livestock production. In North America, rangelands also contain approximately 80% of remaining habitat for grassland birds, a guild of species that has experienced precipitous declines since the 1970s. While livestock grazing management may benefit certain grassland bird species by generating the vegetation structure and density they prefer, these outcomes are poorly understood for avian species breeding in the shortgrass steppe. We evaluated how two grazing management systems, continuous, season‐long grazing and adaptive, rest‐rotational grazing, affected grassland bird abundance from 2013 to 2017 in Colorado's shortgrass steppe. We examined grazing impacts in conjunction with ecological sites, which constitute unique soil and plant communities. When grazing management was evaluated in conjunction with spatial variation in ecological sites, we found three of our five focal bird species responded to grazing management. McCown's Longspur abundance decreased in pastures rested from grazing the previous year. The effect of grazing on Horned Lark and Grasshopper Sparrow depended on ecological site: Horned Lark density was highest in pastures that were intensively grazed and Grasshopper Sparrow density was highest in pastures that were rested the previous year in the least productive ecological site. In addition, densities of all species varied across ecological sites. Our results suggest consideration of soil and vegetation characteristics can inform how adaptive management is applied on a landscape to benefit the full suite of breeding grassland birds, including species that have seemingly contrasting habitat needs. For example, a manager could target adaptive drought mitigation practices, such as resting pastures for 1 yr to generate grassbanks, in less productive soils to benefit grassland birds that prefer taller/denser vegetation structure, or could apply intensive, short‐duration grazing on less productive soils to benefit species preferring shorter/sparser vegetation. A single year of intensive, short‐duration grazing (i.e., one component of our rotational treatment) across the landscape, however, might not create sufficient habitat for species that prefer short/sparse vegetation in our system (e.g., McCown's Longspur). Ultimately, our study indicates how cattle production on rangelands can congruently support grassland bird populations in the shortgrass steppe.

Adaptive management plans rooted in quantitative ecological predictions of ecosystem processes: putting monitoring data to practical use

“…The effect of grazing has previously been investigated in adaptive management schemes. For example, Davis et al (2020) predicted the effect of different grazing regimes on bird population sizes.…”

“…If ecosystems are at least partly controllable (i.e., management actions may have positive effects on biodiversity), then a possible societal response to environmental pressures on biodiversity is to manage ecosystems in order to achieve specified conservation goals. However, due to complicated ecosystem dynamics with considerable time lags, the effects of management actions on biodiversity are often uncertain, and it has been recommended to implement adaptive management plans where our uncertainties regarding the ecological processes are taken into account (Williams et al 2009, Westgate et al 2013, Abrahms et al 2017, Fernández-Giménez et al 2019, Davis et al 2020.…”

“…Typically, the application of the adaptive management approach relies on data from targeted experimental studies to fit relevant predictive ecological models. For example, Davis et al (2020) investigated the effect of grazing management on bird populations in 20 pastures and found significant effects of grazing management, as well as effects of soil and vegetation characteristics, on the bird populations. Such targeted experimental studies are extremely valuable, but they are also relatively expensive and time-consuming endeavours, and here it is suggested to use existing data from ecological monitoring programmes, which often are sampled at relatively large spatial and temporal scales, as the basis for making the predictive ecological models that are needed for applying adaptive management at a local site.…”

Managing for the middle: rancher care ethics under uncertainty on Western Great Plains rangelands

“…Rangeland scientists and conservation biologists have described the correlation between heterogeneous vegetation structure and composition of habitat and biodiversity (Tews et al 2004;Knopf and Samson 1997;Davis et al 2019) and to the importance of prairie dogs as keystone species (Sierra-Corona et al 2015) and fire and heavy grazing as key ecological processes in the Western Great Plains (Skagen et al 2018;Derner et al 2009). In contrast to Bement's model (1969) of optimum stocking, the heterogeneity-based paradigm of rangeland ecology (Fig.…”

“…Grazing experiments have demonstrated that patch burn grazing, and grazing on prairie dog colonies, can have limited negative impact on cattle weight gains in the experimental setting (Derner et al 2006), but ranchers often argue that these management practices have negative financial consequences at the ranch scale (one grazing experiments rarely reach, see Sayre 2017). This complexity explains why ranchers may resist the heterogeneity management Knopf and Sampson (1997) and Davis et al (2019). For maximum biodiversity conservation (Fuhlendorf and Engle 2001) and drought resilience (Derner and Augustine 2016;Agrawal 2008), large ungulate grazing would interact with climate, fire and small mammal grazing to create a large spectrum of rangeland structure, thus supporting a suite of grassland bird species.…”