Diversity across the Landscape
Many grassland wildlife species require specific habitats to thrive, and management recommendations often focus on single species. An example of the complexity associated with managing for multiple species is evident from a study of grassland bird habitat needed by the Horned Lark (Eremophila alpestris) and Grasshopper Sparrow (Ammodramus savannarum) across seven grasslands in five states (Figure 1). These two grassland birds require contrasting habitats, so at first glance a manager would be challenged to mange for them collectively. Yet, these species have co-existed for thousands of years suggesting the importance of heterogeneity. With diversity across the landscape, all species have suitable habitat at some place in the landscape, even though not all space is suitable at a given point in time, and allows all species to persist over an entire area.
Most existing grazing management promotes uniform livestock distribution and forage utilization (left), which reduces diversity of native plant communities and wildlife species. A heterogeneous landscape (right) is critical to the conservation of biodiversity. Photos Samuel D. Fuhlendorf.
Figure 1. Role of habitat structure for two prairie bird species on
seven grasslands (Wiens 1973). These two grassland birds require
contrasting habitats, so managing for Horned Larks manages against
Grasshopper Sparrows and vice versa.
Some wildlife species require a diversity of habitats in different seasons and for different life stages. Managing for uniform distribution of livestock deprives these habitat specialists of the diverse requirements across a landscape that they need to thrive. For example, Lesser Prairie-Chickens (Tympanuchus pallidicinctus), which have declined in range and population by >90% over the last several decades, require diverse habitats (Table 1). Plant communities that are optimum for leking or foraging may not be optimum for nesting success of Lesser Prairie-Chicken. Therefore, if all rangeland is managed to produce uniformity, this species, along with many others will not be present.
Table 1. Habitat Requirements for Lesser Prairie-Chicken (adapted from Taylor and Guthery 1980)
|Habitat||Importance of Disturbance|
|Nesting||Minimal (lightly to ungrazed)|
|Brood Rearing||Minimal to Some (uneven grazing patterns)|
|Foraging||Some (recovering heavily grazed)|
|Leking (booming grounds)||Substantial (fire-grazing)|