Water Is Life: Importance and Management of Riparian Areas for Rangeland Wildlife

Abstract

Water scarcity and climatic variability shape human settlement patterns and wildlife distribution and abundance on arid and semi-arid rangelands. Riparian areas–the transition between water and land–are rare but disproportionately important habitats covering just a fraction of the land surface (commonly < 2% in the western U.S.). Riparian areas provide critical habitat for fish and other aquatic species, while also supporting the vast majority (70–80%) of terrestrial wildlife during some portion of their life cycle. Diverse riparian types serve as vital sources of water and late summer productivity as surrounding uplands dry during seasonal drought. The health and function of rangeland riparian systems are closely tied to hydrology, geomorphology, and ecology. Riparian areas have attracted intense human use resulting in their widespread degradation. Conservation actions, including improved livestock grazing management and restoration, can help maintain and enhance riparian resilience to drought, wildfire, and flooding. This chapter provides readers with an introduction to the importance of riparian areas in rangelands, their nature and ecology, functions for wildlife, and prevailing management and restoration approaches.

1 Introduction

On the range, water is life. Water scarcity and climatic variability are defining features of arid and semi-arid rangelands that shape human settlement patterns and wildlife distribution and abundance (Donnelly et al. 2018, Chap. 3). Riparian areas are the transition zones between water and land and are a critically important anomaly on rangelands. Relative to the broader landscape context, riparian areas are reservoirs of moisture and productivity lying in stark contrast with drier uplands. Commonly occupying only < 2% of the land base today in the western U.S., riparian areas provide disproportionately important resources to wildlife and people (Thomas et al. 1979; Patten 1998; McKinstry et al. 2004). Due to their outsized value and myriad threats, many riparian systems have been degraded or reduced in size over the last two hundred years. Yet, due to the persistence of water and associated plant communities that drive recovery after disturbance, riparian areas are inherently resilient. With active restoration, the potential land that could support riparian conditions may be several times larger than the current footprint (Wheaton et al. 2019a; Macfarlane et al. 2018).

Knowledge of riparian ecology, management, and restoration is increasingly vital for rangeland managers challenged with sustaining productive grazing lands, wildlife populations, clean water, and recreation in the face of growing water demands and climate change (Seavy et al. 2009; Perry et al. 2011). In this chapter, we introduce the importance of managing riparian areas in rangeland ecosystems to motivate and inform conservation and stewardship of these critical habitats. This is not a how-to guide for management but rather an introduction to the subject matter to increase awareness and summarize current knowledge of key riparian concepts, properties, risks, opportunities, and related science. Specifically, we describe what rangeland riparian areas are and why they matter, their nature and ecology, functions for wildlife, and prevailing management and restoration approaches.

2 What Are Riparian Areas and Why Are They Important?

Riparian is an adjective typically defined as “relating to or living or located on the bank of a natural watercourse” (Merriam-Webster 2021), although in an ecological sense, riparian more broadly encompasses diverse ecosystems characterized by the preponderance of water. Riparian areas are habitats that occur along river and stream corridors, meadows and bogs, seeps and springs, wetlands and lakes (Fig. 7.1, NRC 2002). All riparian areas share unique soil and vegetation characteristics that are strongly influenced by free or unbound water in the soil which make them distinct from upland areas. Water availability and source, disturbance regimes, and site conditions, such as geology, soils, and topography, are among the key factors influencing riparian types and plant communities. Biology—especially in the form of vegetation and North American beaver (Castor canadensis)—also interacts with physical conditions to shape riparian form and function (Castro and Thorne 2019; Wheaton et al. 2019a). From a hydrologic standpoint, riparian systems are the interface between open water bodies (channels and ponds) and land connected through surface or subsurface flow (Wilcox et al. 2017). Hydrology can be characterized by flow type: standing water (lentic) or flowing water (lotic), and flow duration: year-round (perennial), seasonal (intermittent), or precipitation-dependent (ephemeral). Perhaps more than any other ecosystem, the structure and function of riparian areas are influenced by interactions between watercourses and the surrounding lands requiring a holistic watershed perspective for management (Gregory et al. 1991).

Fig. 7.1

Types of riparian areas embedded within rangeland watersheds. Riparian areas are rare but diverse ecosystems that occur along river and stream corridors, meadows and bogs, springs and seeps, wetlands, and lakes

Riparian areas perform many functions with on- and off-site effects that yield important ecosystem services to society (NRC 2002). Broad categories of functions include: (1) water and sediment transport and storage, (2) carbon and nutrient cycling, and (3) habitat and food web maintenance. For example, healthy riparian areas play a crucial role in proper watershed function hel** capture, store, and slowly release water thereby attenuating floods and supporting base flows during dry seasons (Elmore 1992). Riparian areas also serve as ‘kidneys’ of the landscape, supporting vegetation buffers that improve water quality by trap** sediment, cycling nutrients and chemicals, and filtering pollutants from the watershed (Hook 2003; Mayer et al. 2006; Swanson et al. 2017). Finally, riparian areas function as habitat, providing food, cover, water, refugia, and movement corridors for rangeland wildlife.

Particularly in arid ecosystems, riparian areas are hotspots of biodiversity supporting 70–80% of vertebrate species during some stage of their life cycle (Thomas et al. 1979; Brinson et al. 1981; Naiman et al. 1993; Knopf 1985). Wildlife use of riparian systems is disproportionate to its availability (Thomas et al. 1979; McKinstry et al. 2004). This is best documented for migratory birds (Knopf et al. 1988) where species richness in riparian habitats can be 10–14 times higher than adjacent uplands (Stevens et al. 1977; Hehnke and Stone 1979). Over half of all bird species are completely dependent upon riparian areas in the desert southwest (Johnson and Jones 1977). Of course, riparian habitats are essential to fish and other aquatic and semi-aquatic species in water-limited rangelands (Saunders and Fausch 2007). Perhaps less appreciated is how important seasonal floodplain habitats are for many species of fish (Opperman et al. 2017). Numerous species of mammals (small and large), amphibians and reptiles, and invertebrates, including pollinators, depend on healthy riparian habitats at some point during the year. For example, on rangelands of southeastern Oregon, 288 of 363 terrestrial species (80%) are directly dependent upon riparian areas or use them more than other habitats (Thomas et al. 1979).

Euro-American fur trap** and homesteading patterns also highlight the historical importance of riparian areas to people and working lands across western North America. In the early 1800’s, abundant beaver in western waterways attracted fur trappers and fueled Euro-American expansion (Dolin 2011; Goldfarb 2018). Later in the century, homesteading pioneers sought out water and associated riparian areas to allow agriculture in an environment where soils and climate make land less arable. While most rangelands in the Intermountain West are publicly owned, 50–90% of riparian areas are privately-owned (Donnelly et al. 2018). In grasslands of the Great Plains, the proportion of privately-owned riparian areas is even higher. For over two centuries, riparian systems have helped supply reliable water that is the lifeblood of commerce and rural communities, supporting irrigation of crops, livestock grazing, development, mining, recreation, and other activities.

Riparian areas contribute to overall rangeland resilience and resistance to sudden change during drought, wildfire, and flooding, providing a buffer against increasing climate variability and extreme weather events (Seavy et al. 2009). Management and restoration of degraded riparian areas improves drought resilience by boosting soil moisture storage and floodplain vegetation productivity (Silverman et al. 2018; Fesenmeyer et al. 2018). Fully functioning riparian areas are better able to resist wildfire damage (Fairfax and Whittle 2020), providing refugia for wildlife and livestock in burned landscapes in an era of increasing fire size and frequency, and better preparing watersheds for extreme floods (Perry et al. 2011). Restoring riparian areas is key to increasing resilience and maintaining the capacity of these systems to provide ecosystem services in the face of climate change and long-term drought (Seavy et al. 2009; Capon et al. 2013; Williams et al. 2022).

3 Reading the Riparian Landscape

Riparian areas are an expression of watershed-scale processes because they are located in relatively low spots on the landscape where water and sediment collect (Wilcox et al. 2017). Geology, hydrology, and biology interact as primary drivers of riparian form and function (Castro and Thorne 2019). While some riparian types are primarily groundwater-driven (e.g., springs), surface water flow and sediment movement within watersheds are particularly important in sha** the condition and extent of most riparian areas (NRC 2002). Diverse vegetation communities arise from variation in water availability, flow and disturbance regimes, soils, and climate. A mosaic of habitats can exist ranging from persistently saturated wetlands, to ephemerally inundated floodplains, to meadows supported mainly by high water tables and wetted only during periods of runoff. Given the high degree of connectivity (vertically and laterally) of riparian systems to both adjacent water bodies and surrounding uplands that feed and define them, a holistic geomorphic perspective is helpful when assessing function, condition, and potential.

On rangelands, the bulk of riparian areas are associated with fluvial systems, such as streams and rivers. Best viewed as riverscapes, stream and riverine landscapes are composed of floodplains and channels that together comprise the valley bottom (Fig. 7.2, Ward 1998; Wheaton et al. 2019a). The valley bottom reflects the maximum possible extent that could be occupied by riparian vegetation. Valley bottoms may consist of one or more of these building blocks: active channels and active floodplains (i.e., areas experiencing flooding thereby capable of supporting riparian vegetation), and inactive floodplains (i.e., disconnected areas that could plausibly flood and support riparian vegetation if conditions improved). Not all riverscapes have all building blocks and the valley setting helps determine what is natural and expected. For example, a steep confined gorge may only have a single active channel. In contrast, some riverscapes in lower gradient settings (e.g., wet meadows) have only active floodplains and no natural channels. Sometimes riverscapes are separated from hillslopes by other geomorphic features like terraces (i.e., valley bottoms from a relic or historic flow regime), moraines (i.e., accumulated debris from past glacial activity), or fans from tributaries (e.g., alluvial fans). Assessing riverscapes to identify the valley bottom building blocks and other related geomorphic features helps set appropriate expectations for the intrinsic potential of riparian areas in fluvial systems (Fyrirs and Brierley 2013; Wheaton et al. 2015).

Fig. 7.2

Planform and cross-sectional views showing geomorphology of a hypothetical riverscape in an intact (a) and degraded scenario (b). Reading the riverscape valley bottom is important as it reflects the maximum potential extent of riparian vegetation. Intact riverscapes (a) support a higher water table and more riparian vegetation, while incised or channelized riverscapes (b) result in a lower water table with less riparian potential. The valley bottom includes the area that could plausibly flood in the contemporary flow regime and is made up of the active channel(s), active floodplain, and/or inactive floodplain. Restoration to improve connectivity of inactive floodplains may be required in degraded systems to fully realize riparian potential. Figure adapted by Adrea Wheaton from Wheaton et al. (2019b) and licensed under a Creative Commons Attribution 3.0 United States License

Rangeland managers are often tasked with assessing riparian condition, a challenging responsibility given the diverse and dynamic nature of these systems. However, hydrologic, soil/geomorphic, and biological attributes and processes provide clues to riparian area condition and function (Dickard et al. 2015; Wheaton et al. 2019a; Gonzalez and Smith 2020). In general, properly functioning riparian areas are dynamic environments that have adequate space and other characteristics to accommodate water runoff, dissipate energy, and adjust to change (Fig. 7.2a). They can expand and contract within the confines of their natural valley bottom in response to disturbances like floods and droughts (Whited et al. 2007). They also support the kinds and amounts of vegetation needed to stabilize soils, capture sediment, and slow and attenuate surface and subsurface flows. Properly functioning ecological processes in riparian areas, like beaver dam activity, vegetation recruitment, and wood accumulation, provide structural elements that increase habitat complexity and build resilience (Silverman et al. 2018; Wheaton et al. 2019a).

A variety of impairments occurring at watershed to site-specific scales can reduce riparian condition. Watershed land cover changes due to catastrophic wildfire, improper grazing, woodland expansion, development, or other factors impact watershed hydrologic function and can lead to riparian degradation. Intensive land uses located within valley bottoms like roads and associated infrastructure, water diversion, and cultivated agriculture can directly limit riparian functions and potential extent (i.e., the area capable of supporting riparian vegetation). Channel incision—downcutting of channel bed elevation through erosion—is a widespread symptom of degradation in rangeland watersheds resulting in predictable changes in riparian condition (Cluer and Thorne 2013; Dickard et al. 2015; Gonzalez and Smith 2020). Incision reduces the potential for riparian vegetation within valley bottoms by lowering the water table and disconnecting channels from active floodplains (Fig. 7.2b). Learning to recognize impairments and the degree of incision are critical to informing management actions and appropriate expectations for riparian areas (Skidmore and Wheaton 2022).

4 Ecology of Riparian Areas

4.1 Vegetation

A defining attribute of riparian ecology is the distinct vegetation arising from increased water availability. In rangelands, this riparian vegetation often forms a green strip adjacent to drier uplands during annual summer droughts. Vegetation is indicative of hydrologic function in riparian areas (Table 7.1, Lichvar et al. 2012, 2016; USACE 2018). Hydrophytic, or water-loving, vegetation includes plants specifically adapted to grow in low oxygen (i.e., anaerobic) environments. Specific plant species occur along a gradient of wetted conditions, such as, obligate species in water or saturated soils, facultative wetland species in frequently wet soils, or facultative species in soils that fluctuate between wet and dry (USACE 2018). Other vegetation less capable of withstanding anaerobic conditions are facultative upland and upland species that typically occur in drier environments and can be used to identify non-wetland areas (USACE 2018). Common herbaceous riparian plants include graminoids such as sedges (Carex spp.), rushes (Juncaceae spp.), and wet-adapted grasses (Poaceae spp.). Typical woody riparian species include a diversity of willows (Salix spp.), cottonwoods (Populus spp.), and alders and birches (Betulaceae spp.). Riparian plant composition is highly variable and a product of climate, hydrologic regime, soils and geomorphology, land use, species distribution, and other factors (NRC 2002; Hough-Snee et al. 2014). Healthy riparian plant communities exist in a wide variety of forms ranging from relatively simple and stable herbaceous mats consisting of just a few species, to dynamic and diverse woody-dominated riparian shrublands and forests.

Table 7.1 Vegetation provides clues to hydrologic function in riparian areas

Vegetation plays a critical role in the structure and function of riparian systems as well as the broader rangeland water cycle (Wilcox et al. 2017). Above ground, plants provide surface roughness to redistribute flow patterns and facilitate deposition and soil building (Manners et al. 2013). Many riparian plants have adaptations to withstand stream or overland flows, such as cordlike rhizomes, fibrous root masses, coarse leaves, and strong flexible crowns (Winward 2000). Structurally forced changes in flow patterns produce physically diverse and complex habitats and enhance resilience to disturbance (Corenblit et al. 2007; Wheaton et al. 2019a). For example, in-stream wood accumulation affects water velocities and depths, sediment erosion and deposition, and provides organic material essential to support diverse aquatic species (Wheaton et al. 2015). Below ground, riparian plants tend to have very dense root systems (Manning et al. 1989) that bind soil particles, provide stability, and slow runoff. Healthy plant roots create macropores and soil organic matter that improve infiltration of surface runoff and water-holding capacity of soils, increasing residence time of water. Riparian vegetation creates unique microclimates that affect water temperatures and humidity. Forested riparian areas support large wood accumulation important to stream processes and aquatic habitat.

Riparian vegetation can be prone to damage owing to disproportionate use by livestock, free-roaming horses, wildlife, and people. While erosion and deposition are natural processes in riparian systems, degradation of vegetation can result in predictable changes affecting form and function (Cluer and Thorne 2013). If hydrophytic vegetation is damaged, the resulting loss of structure often leads to reductions in riparian stability. Improper grazing and trailing by livestock, free-roaming horses, and big game can reduce plant health and vigor, leaving riparian areas more vulnerable to accelerated erosion. Stream systems may incise, and wet meadows may develop channels which cause the water table to drop, drying out the soil and converting the riparian area to more upland vegetation with less robust root structure (Wyman et al. 2006). Careful management of grazing animals in riparian areas is required to support a variety of functions and values.

4.2 Beavers: Ecosystem Engineers

The North American beaver is a keystone riparian species with a unique role in sha** the form, function, and ecology of many riverscapes. Often referred to as an ecosystem engineer, beaver have a profound influence on riparian environments, producing diverse habitats required by many other wildlife species. Modifications occur through foraging primarily on woody plants and activities associated with dam building including construction of ponds, lodges, canals, tunnels, and burrows. These activities trigger a cascade of effects altering riparian function and diversity, aquatic food webs, geomorphology, hydrology, and biogeochemical cycling (see reviews in: Brazier et al. 2020; Wohl 2021). The functional role of beaver in riparian areas has been increasingly recognized as an integral part of stream evolution, riparian ecology, and conservation (Stoffyn-Egli and Willison 2011; Pollock et al. 2014; Castro and Thorne 2019; Jordan and Fairfax 2022).

Prior to Euro-American arrival, an estimated 60–400 million beaver occupied North America (Seton 1929). Beaver dam activity created some 25–250 million ponds (Pollock et al. 2003) with a total surface area of approximately 230,000 square miles, equivalent to the land area of Arizona and Nevada combined (Butler and Malanson 2005; Goldfarb 2018). Highly prized for their fur, beaver trap** began in the late 1500s, and by the early 1800s they were harvested to near extinction (Dolin 2011). With the removal of these industrious rodents, unmaintained dams often breached leading to the draining of hundreds of millions of ponds and wetlands (Ott 2003; Goldfarb 2018). While the arrival in the late 1800s of irrigated agriculture, timber harvest, overgrazing, and mining impacted western watersheds, legacy effects of the loss of beaver and their dam-building activities are often underestimated and forgotten (Wohl 2021). In the early 1900s, the important role of beaver in sha** riverscapes started to be recognized with conservation and relocation efforts occurring over the next century. Populations are now estimated between 6 and 12 million and, although still far less than their historic abundance, beavers have re-colonized much of their former range across North America (Naiman et al. 1988).

Beaver basically require water and vegetation to make a living, occupying diverse riparian ecosystems from boreal forest to deserts (Brazier et al. 2020; Larsen et al. 2021). Beaver are herbivores, consuming herbaceous plants and cambium (i.e., the inner bark of woody plants). Their diet varies greatly across different environments and seasons. In colder climates, for example, herbaceous plants may comprise a majority of their diet, especially in the summer. In lotic systems, during winter they often switch to more woody species that are harvested and stored in deep water caches that can be accessed below ice from underwater entrances to their lodges (Milligan and Humphries 2010). As central place foragers, beaver select vegetation based on size and palatability depending on availability and distance from their lodge or pond (Mahoney and Stella 2020). Highly preferred plant species, such as aspen and willow, have coevolved with beaver and regenerate, often with increased vigor, after they have been cut (Runyon et al. 2014). Beaver may greatly reduce preferred riparian vegetation within their home range forcing them to move to new areas to access forage while the depleted stand regenerates, acting much like coppice foresters seeking to stimulate plant growth by cutting back plants (Hall 1970). As a result, beaver create a shifting mosaic of riparian habitat types within riverscapes that support varying structural diversity, plant composition and richness, and seed or sprout production (Mahoney and Stella 2020).

While beaver can be awkward on land, they are powerful swimmers that prefer water deep enough to evade predators. In some systems, water is sufficiently deep to provide this protection, rendering dam building unnecessary. In shallower streams common across rangelands, however, beaver typically build dams to slow down and deepen water to escape predation and allow for more extensive harvest and transport of wood and vegetation within the refuge of water. Beaver often incorporate larger woody material into dams and lodges, along with smaller branches that are consumed or stored in the bottom of the ponded area. The influx of woody material and the creation of dams and canals enhance hydraulic and geomorphic complexity (e.g., sediment sorting) producing physically diverse habitats. Slower ponded areas with accumulated fine sediment can create anaerobic conditions that alter biogeochemical cycles (Naiman et al. 1988; Murray et al. 2021). Diversity in hydraulics, physical habitats, substrate, and riparian structure, creates more complex habitat often supporting a higher diversity of stream fauna (Burchsted et al. 2010; Bouwes et al. 2016).

Beaver dam activity is an important ecological process influencing stream evolution creating multithreaded, complex reach types (i.e., “stage 0” in Cluer and Thorne 2013). Furthermore, structural changes caused by beaver dam activity can accelerate recovery of incised riverscapes by facilitating widening, aggradation (i.e., deposition of material by current), and floodplain reconnection (Fig. 7.3, Pollock et al. 2014). By increasing both aggradation and water depth, beaver dams enhance frequency and duration of floodplain inundation even during baseflows. Higher water surfaces increase water table elevations and create greater hydraulic gradients resulting in elevated exchange of surface and groundwater (Majerova et al. 2015). Thus, dams increase vertical and lateral hydrologic connectivity allowing water to be stored during high flow events (Westbrook et al. 2020). Stored water is more slowly released over the descending limb of the annual hydrograph resulting in improved drought resilience (Fesenmeyer et al. 2018; Silverman et al. 2018). In a similar but compressed time frame, beaver dams and dam complexes help attenuate high flows (Westbrook et al. 2020) and reduce unit stream power, dissipating energy by spreading flow onto adjacent floodplains reducing the likelihood of channel incision (Pollock et al. 2014). Greater inundation and soil moisture not only increase vegetation recruitment and vigor but also improve riparian resistance to fire and drought (Fairfax and Whittle 2020). Thus, beaver confer resiliency to riverscapes that can help them withstand multiple disturbances that are likely to become more intense with climate change.

Fig. 7.3

Beaver dam activity accelerates stream evolution from an incised (a) to anastomosing riverscape (f) (from Pollock et al. 2014). This series illustrates the typical progression: a beaver build dams in an incised channel that has been disconnected from the active floodplain, b high stream power results in beaver dams failing by end cutting, forcing water to erode the bank leading to channel widening, c inset floodplains begin to form in the widened trench and a widened channel facilitates sediment capture, d sediment captured behind the dams also aggrades the channel and facilitates riparian vegetation establishment, e dams raise the surface water reconnecting the stream to the formerly active floodplain, and f beaver dam activity creates well-connected and vegetated riparian area across the valley bottom

4.3 Riparian Functions for Wildlife

Biotic and abiotic factors combine in riparian areas to create habitat for aquatic and terrestrial wildlife found nowhere else on rangelands. The disproportionate diversity and abundance of life in riparian systems stems from their ability to provide water, food, cover, refuge, and migration corridors needed to fulfill annual life cycle requirements (Fig. 7.4). Greater availability of water in riparian areas than uplands gives rise to higher productivity of vegetation and insects, and a more dependable source for water consumption, which becomes increasingly important during seasonal summer drought. Diverse vegetation communities provide breeding, nesting, rearing, loafing, feeding, and escape cover needed by most terrestrial rangeland wildlife at some point in the year (Thomas et al. 1979). Habitat connectivity is also provided by riparian corridors and wetlands interspersed across rangeland watersheds, facilitating movement, dispersal, and migration.

Fig. 7.4

Examples of riparian functions for wildlife. Riparian areas provide critical habitat needed by most rangeland wildlife to fulfill annual life cycle requirements, such as a breeding cover for amphibians, b nesting and brood-rearing cover for birds, c water, forage, and calving cover for big game, and d refugia from wildfire. Photo credits a–d: Jeremy Maestas, Richard Van Vleck, Nathan Seward, Joseph Wheaton

Reliance on riparian areas by migratory birds is well documented (Johnson et al. 1977; Knopf et al. 1988). Each year in the spring, millions of neotropical songbirds return to breed in western riparian areas after wintering in Mexico, and Central and South America. Over 80% of migrant birds breed in riparian areas in some locations (Knopf 1985). Riparian vegetation and insects supply necessary food and cover for nesting, rearing, and fledging. Landbird abundance and richness are closely tied to structural heterogeneity of riparian vegetation (Anderson and Ohmart 1977; Rich 2002; Brand et al. 2008; Cubley et al. 2020). Given this connection, assessment of breeding bird presence and abundance can serve as an indicator of riparian health and plant structural complexity (Rich 2002). Following the breeding season, riparian areas provide valuable stopover habitats for neotropical birds during the fall migration south. Waterfowl, shorebirds, and waterbirds all rely on wetland, meadow, and playa riparian habitats in rangelands for breeding and stopovers supporting spring and fall migrations (Donnelly et al. 2019; Haukos and Smith 1994).

Riparian areas are important in meeting seasonal habitat needs for imperiled resident birds and can influence landscape carrying capacity (Donnelly et al. 2018). Sage-grouse (Centrocercus urophasianus), known for their dependency on sagebrush steppe, “follow the green line” as uplands dry out in the summer to reach riparian areas and other mesic habitats (i.e., areas with adequate moisture for plant growth), such as high elevation habitats and irrigated fields, that provide abundant forbs and insects to feed growing chicks (Chap. 10). Mesic resource abundance and drought resilience influences the distribution and abundance of sage-grouse where other life requisites have been met (Donnelly et al. 2016, 2018). Columbian sharp-tailed grouse (Tympanuchus phasianellus columbianus) utilize riparian zones as well for winter food and cover, foraging on the buds of woody vegetation (Giesen and Connelly 1993). Numerous other more common landbirds including non-migratory songbirds, quail, and raptors also use riparian habitats in various seasons.

A host of aquatic and semi-aquatic species would not exist in rangelands without riparian ecosystems. Aquatic and riparian zones are intricately linked through exchange of invertebrate prey, plant material, and water affecting food webs and habitat quantity and quality. Riparian vegetation supports terrestrial invertebrate inputs to streams that can constitute half of the food resources for fish like salmonids (Baxter et al. 2005; Saunders and Fausch 2007). Riparian leaf fall and woody debris also retain and support aquatic food webs and provide for added aquatic habitat complexity for a diversity of aquatic species and various life stages (Gregory et al. 1991). Conversely, emergence of aquatic insects also feed terrestrial wildlife including bats, birds, reptiles, and amphibians. Wetlands, beaver ponds, and floodplains support unique amphibians year-round (Munger et al. 1998; Arkle and Pilliod 2015). Healthy and hydrologically functioning riparian areas ensure habitat connectivity that allows water-reliant species to disperse and migrate. Although much less well known, rangeland springs are home to many species of springsnails (Pyrgulopsis spp.), one of the most abundant and diverse groups of endemic organisms in the region (Hershler et al. 2014), and a diversity of other aquatic biota (Sada et al. 2001).

Small and large mammals rely on riparian areas for water, foraging, cover, movement, and migration corridors. Riparian areas provide productive foraging habitat for bats (Holloway and Barclay 2000), and riparian woodlands supply roost sites in otherwise treeless rangelands (Williams et al. 2006; Trubitt et al. 2018). Mule deer (Odocoileus hemionus) and elk (Cervus canadensis) frequent riparian zones, especially during summer months after fawning and calving (McCorquodale 1986; Morano et al. 2019). In the Great Basin, where mule deer habitat selection is largely driven by forage availability and water, deer select habitats closer to riparian areas especially in areas that are hotter and drier (Morano et al. 2019). In late summer, riparian areas provide productive and nutritious forage, shade, and water for all grazing animals, wild and domestic.

Riparian ecosystems play a crucial role in reducing wildlife vulnerability to climate change, providing refugia and adaptation opportunities (Seavy et al. 2009; Capon et al. 2013). Riparian vegetation provides shade and microclimates that give thermal refuge to animals adjusting to warmer air or water temperatures. Beaver dam activity produces fire-resistant riparian corridors that provide important refugia during wildfire, especially for species unable to physically escape the spread of flames (Fairfax and Whittle 2020). Well-connected riverscapes provide opportunities for water-dependent species to move to more hospitable parts of the watershed as climate conditions dictate.

5 Management and Restoration

Proper stewardship of riparian resources through a holistic watershed approach helps ensure maintenance of vital ecosystem services and goods for society. While there are many conservation actions land managers can take, promotion of ecological, hydrologic, and geomorphic processes underpins all successful approaches (NRC 2002; Goodwin et al. 1997). At the most fundamental level, water availability sets the stage for riparian ecology, so protection and restoration of hydrology is of paramount importance. Livestock grazing is a nearly ubiquitous land use on rangelands that has direct and indirect effects on riparian function, from influencing watershed hydrology to direct changes to riparian vegetation (Kauffman and Krueger 1984; Elmore 1992; Belsky et al. 1999; Wilcox et al. 2017). Widespread channel incision in riparian areas reflects a legacy of degradation that may be unrelated to current management (Chambers and Miller 2004) but often requires active intervention to reverse (Zeedyk and Clothier 2009). In this section, we highlight a few of the prevailing concepts and strategies for riparian management, protection, and restoration.

5.1 Grazing Management

Negative effects of overgrazing in riparian areas are well documented (Kauffman and Krueger 1984; Belsky et al. 1999). Less well understood are the complex relationships between contemporary grazing and legacy effects of historical riparian degradation due to other factors, such as the fur trap** era of the 1800s (Ott 2003), unregulated grazing during the late 1800s to early 1900s prior to reserving National Forests or the Taylor Grazing Act of 1934, water diversion and development during most of the 1900s, and more recently invasive species, climate change, and wild and free-roaming horses. “Passive” restoration through establishment of riparian exclosures that remove livestock grazing can result in riparian improvement but may not be sufficient to fully restore valley bottoms that have sustained drastic geomorphic alteration. In part, this is because the protection is usually limited to an already diminished remnant riparian area. Furthermore, livestock exclusion is often not feasible or desirable on western working lands where most riparian areas are in private ownership and support grazing operations. Fortunately, much has been learned in recent decades about compatible strategies for managing grazing to maintain and promote riparian functions and values (Text box 7.1; Platts 1991; Elmore 1992; Wyman et al. 2006; Swanson et al. 2015).

Text Box 7.1: Riparian recovery through improved grazing

On Susie Creek, Nevada, riparian conditions improved dramatically following changes in grazing strategies by the Maggie Creek Ranch and Bureau of Land Management (BLM) (Swanson et al. 2015; Charnley 2019). This photo series chronicles recovery following a switch from decades of growing-season-long cattle grazing (a) to a combination of spring and/or fall grazing, hot season grazing and periods of rest from grazing over 28 years (b–f). In 1992, the riparian area in this wide gully (formed by incision in about 1910) was fenced into a riparian pasture and no longer grazed throughout the growing season every year. Subsequently, riparian plants expanded, slowed water forces, captured sediment, and stabilized streambanks resulting in a vegetated floodplain and elevated water table (b). With willows available, beavers accelerated the process of rehydrating the gully, creating expansive areas of ponded water and wetland vegetation (c). Beaver activity led to conversion of the willow community to other types of riparian plant communities, including a short-lived cattail marsh (d). A functional and well vegetated floodplain within the old gully continues to evolve (e–f). Riparian recovery improved resilience to flooding (including a rain on snow event in 2017), wildfire, and drought (Fesenmeyer et al. 2018). In the severe drought of 2020, abundant green riparian vegetation thrived with below ground summer water storage and, in the fall, water came to the surface in more locations. In this high-sediment watershed, aggradation in the widened gully is raising the water table across the valley bottom and providing critical green forage and water for wildlife and livestock, especially during summer and fall. The BLM and ranchers continue to fine tune and adjust management based on observed changes in weather/flows, vegetation, sediment deposition, and management effects in this dynamic riparian area. The Susie Creek story is just one of many examples of the outcomes possible following collaborative, private-public efforts to improve grazing management (also see: https://www.youtube.com/watch?v=kSctr0aQOso and https://iwjv.org/new-video-changing-a-landscape-to-a-lifescape/) Photos by: Carol Evans, retired fisheries biologist, Elko District, Bureau of Land Management (1988–2016).

Similar to wildlife reliance on riparian resources, livestock on the range often depend on these systems to complete their life cycle. Livestock need water daily and riparian areas can be a primary source to meet those requirements. When upland plants dry out in hot summers or dry seasons, riparian areas remain green providing more nutritious forage which further attracts livestock to valley bottoms. Overgrazing can occur when plants are stressed by repeated defoliation without adequate time for recovery, or when trampling damages soils, which weakens riparian plant roots, destabilizes streambanks, and lowers the water table. Addressing overgrazing often involves changes in stocking rate (or the number of grazing animals in a given area for a specific time period) and/or livestock distribution (i.e., where animals are allowed to graze) and timing (i.e., when animals are allowed to graze). Stocking rate reductions often have to be severe to effect change in riparian conditions, which may be impractical in working landscapes. This is because riparian valley bottoms are typically only a small fraction of larger grazing pastures where stocking rates are set, and livestock tend to stay concentrated near water regardless of how many animals are present. Therefore, manipulation of livestock distribution and timing are often important strategies in minimizing overgrazing in rangeland riparian areas.

Riparian area grazing management is more likely to be successful if it enables control of, and variation in, periods of grazing and recovery, livestock distribution, and intensity of use (Swanson et al. 2015). Effective grazing strategies prevent repeated or excess damage to valley bottom soils and plants when they are most susceptible to grazing-related stresses (Wyman et al. 2006). Grazing management should be designed to balance grazing periods with opportunities for plant growth and recovery, and/or providing retention of adequate leaf area on individual plants post-grazing (Swanson et al. 2015). Rotation or variation in timing of grazing prevents stress in the same season year after year so plants can successfully complete all phases of their annual life cycle. By actively managing livestock, grazing impacts can be controlled to ensure plant growth or regrowth before, during or after grazing. Grazing management actions and monitoring are most effective when they embrace the interdependence of public and private lands.

Grazing managers have access to a wide variety of strategies for riparian-focused management to accomplish objectives and allow recovery (Table 7.2). A fundamental choice driving management actions, grazing criteria, and methods for short-term or implementation monitoring is whether to build management around: (a) schedules of grazing and recovery, or (b) limiting utilization levels within the growing season (Boyd and Svejcar 2004, 2012). To ensure appropriate management and enable sufficient flexibility to adapt management as riparian areas change, a plan should be written around a set of core principles that inform selection of locally targeted grazing use indicators. Such principles allow for flexibility and success in each pasture. Grazing use indicators and criteria should fit the chosen treatments and strategies to achieve resource objectives (University of Idaho Stubble Height Study Team 2004). Table 7.2 couples a suite of effective strategies with relevant implementation monitoring indicators. Rationale for how and why strategies work is described in Swanson et al. (2015), and recommendations for monitoring long-term effectiveness and short-term implementation is provided in Burton et al. (2011), Dickard et al. (2015), Swanson et al. (2018), and Gonzalez and Smith (2020).

Fencing is an important tool for facilitating many of the strategies described in Table 7.2, but establishing physical fences creates additional costs and liabilities for land managers (Knight et al. 2011) and impacts wildlife behavior and movements (Jakes et al. 2018) so new fences should be carefully planned. Alternatives to physical fencing, such as herding and stockmanship techniques (Cote 2019) or manipulating water/salt/supplement placement, may also be appropriate to effectively implement riparian grazing strategies (Table 7.2). Virtual fencing is an increasingly viable technology for achieving riparian improvements while minimizing risks associated with traditional fencing (Campbell et al. 2018; Ranches et al. 2021; Boyd et al. 2022). For example, virtual fencing could be used to allow only part of a stream, part of a large wetland, or each one of a series of springs in a spring complex to be accessed by livestock at any one time, thereby decreasing the duration of grazing and increasing recovery time. While a variety of techniques can be used to manage livestock, riparian functions may continue to be impaired in some instances by wild and free-roaming horses or grazing wildlife unless animal populations are maintained at an appropriate management level (USDI 2010).

Table 7.2. Riparian grazing management strategies that often support riparian functions and recovery

5.2 Protection and Restoration

5.2.1 Riparian Planting

Where riparian plant communities have been lost or severely reduced, changes in management alone may be insufficient to recover them so revegetation is required. Re-establishment of riparian vegetation, often referred to as buffers, can improve water quality and shading, habitat for fish and wildlife, and overall riparian function. Matching the appropriate plant species to site conditions is key to success. Hydrology is a primary determinant of vegetation composition and unique species are adapted to varying degrees of inundation and soil moisture (Hoag et al. 2008). All too often, riparian planting is done in degraded riparian areas without first addressing the hydrology, geomorphology, or grazing management needed to sustain riparian vegetation, leading to chronically low success rates. Realistic planting zones, based on the elevational and lateral relationships of vegetation to surface and subsurface water, should be used to guide planting plans (Hoag et al. 2001). Consideration of species composition and structural diversity is also important in meeting life history needs of wildlife, especially birds (Gardner et al. 1999). A common misperception is that all riparian areas support woody vegetation, but many systems naturally do not because of water source, gradient, soils, climate, or other factors. Site-specific conditions, along with local reference areas, should be used to guide species selection and placement (Hoag et al. 2001). Techniques for revegetation include use of live cuttings from certain woody species (e.g., willows, cottonwoods), transplanting of bare root or container stock plants, and seeding (Gardner et al. 1999). Degraded riparian areas can be havens for invasive species (Stohlgren et al. 1998), such as reed canarygrass (Phalaris arundinacea), salt cedar (Tamarix spp.), and many others, so planting efforts typically require measures to control competition and follow-up management of weed infestations. Long-term success of revegetation hinges on compatible grazing management, invasive species control, and promotion of essential riparian processes (e.g., hydrology, disturbance regime) needed to support and recruit new native vegetation through time (Stromberg 2001).

5.2.2 Floodplain Reconnection

Levees, dams, roads, constructed channels, channel incision, and other impairments have greatly reduced the proportion of active floodplain within valley bottoms of many riverscapes (Tockner and Stanford 2002; Skidmore and Wheaton 2022). Thus, a common restoration strategy is to reconnect former floodplains. Multiple restoration approaches are used to achieve this goal, such as channel reconstruction and remeandering (e.g., Natural Channel Design, Rosgen 2011), levee and riprap breaching or removal, floodplain lowering, dam and barrier removal, road decommissioning, and increased instream flows/flood regimes from dam releases. These approaches to floodplain reconnection, typically applied in larger streams and rivers, require engineering design and expertise, heavy equipment operators, and special permits especially where infrastructure vulnerability is high. While important, these approaches are expensive (Bernhardt et al. 2007) and may not be practical to address the scale of degradation of riverscapes, particularly across vast rangelands. Alternative approaches that rely on grading, but are still cost effective and process-based, include the “geomorphic grade line” approach to achieving Stage 0 (Powers et al. 2018). Approaches and techniques selected to enlarge or reconnect floodplains depend on stream size and type, hydrology, accessibility, risks, budgets, and timelines for recovery.

Smaller headwater streams of rangeland watersheds are often overlooked for restoration opportunities but represent the vast majority of riverscape miles across much of the West. Here, low-tech processed-based restoration approaches (Wheaton et al. 2019a, b; Zeedyk and Clothier 2009) can be effective, cost-efficient, and scalable solutions to achieve floodplain reconnection (Text Box 7.2). For example, simple hand-built structures (e.g., post-assisted log structures, beaver dam analogues) can be used to mimic and promote important processes of wood accumulation and beaver dam activity that increase connectivity with active floodplains (Pollock et al. 2014; Wheaton et al. 2019a, b).

Text Box 7.2 Low-tech process-based restoration

Bridge Creek, Oregon, was historically subject to intensive grazing, timber harvest in the upper watershed, and beaver trap**. Large storm events in the early 1900s led to massive valley fills, followed quickly by channel incision resulting in a lowered water table and loss of riparian vegetation. Much of the creek became a highly simplified channel disconnected from its floodplain, representative of incised streams commonly found in rangelands. Early management to reverse degradation included removal of livestock grazing, allowing some willow recovery along the channel margins. Beaver reoccupied the creek with increasing vegetation. Sediment aggraded quickly behind beaver dams, but because of the force of high flows in the incised trench and the small woody material available, the dams were short-lived.

In a watershed-scale experiment, Bouwes et al. (2016) piloted low-tech process-based restoration using beaver dam analogues (BDAs) to improve aggradation, beaver dam longevity, and floodplain connectivity. Researchers installed 121 BDAs in Bridge Creek and compared hydrologic, geomorphic, and ecological responses to a control watershed [see sample treatment reach (a) and reference reach (b)]. Within 4 years, the BDAs accelerated beaver dam activity nearly eightfold. The increase in dam density and stability captured sediment, raised the stream bed, and reconnected the channel with its floodplain leading to higher groundwater storage, surface water temperature diversity (Weber et al. 2017), and increased fish habitat quantity and complexity. Importantly, these changes produced population-level benefits for threatened steelhead (Oncorhynchus mykiss), representing a rare example in the scientific literature documenting a positive fish population response following restoration.

5.2.3 Wet Meadow Protection and Restoration

Wet meadows can be particularly vulnerable to loss and degradation due to channel incision, improper grazing and animal trailing, roads, intentional drainage, land use conversion, and altered watershed hydrology. A variety of strategies are used to protect functional meadows that remain and restore those that have been impacted. Given the preponderance of wet meadows in private ownership (Donnelly et al. 2018), conservation easements can be an important tool used to keep wet meadows intact, preventing loss of wetland and meadow habitats to other land uses (e.g., tillage agriculture, development, water diversion). Incentive-based easement programs, such as those administered by the U.S. Department of Agriculture Natural Resources Conservation Service, offer compensation to landowners who voluntarily agree to protect wet meadows and forego certain activities. Easements have been used to protect critical rangeland wildlife habitats across the West, such as playas and prairie potholes for waterfowl, meadows for sage-grouse, and mule deer migration corridors (Doherty et al. 2013; Copeland et al. 2014; NRCS 2015).

Channel incision is a widespread impairment affecting meadow function that has been the focus of restoration in the western U.S. for over a century (Kraebel and Pillsbury 1934; Ramstead et al. 2012). Early in the gully erosion process, simple low-tech restoration methods can be effectively used to stop headcut advancement and reconnect meadows to floodplain surfaces (Text Box 7.3, Zeedyk and Clothier 2009; Maestas et al. 2018). As the incision trench deepens, more intensive restoration involving heavy equipment and earthwork is often conducted, such as, pond-and-plug techniques where gullies are partially filled and water returned to the historic meadow elevation (Rosgen 1997; Zeedyk and Vrooman 2017; Rodriguez et al. 2017). Alternatively, process-based restoration approaches (e.g., geomorphic grade line or low-tech) have been used in systems where it is possible to leverage natural processes of erosion and deposition to help aid in rebuilding healthy, connected floodplains (Powers et al. 2018; Wheaton et al. 2019a). Roads in valley bottoms can cause or exacerbate incision so relocating them to uplands outside or along the margin of the valley bottom or creating hardened crossings may be part of restoration planning (Zeedyk 2006). Restoration success is linked to grazing strategies that promote wetland and meadow vegetation, and practices like riparian pasture fencing, offsite water, and drift fencing may be needed to discourage livestock and wild ungulates from congregating and trailing in meadow bottoms (Wyman et al. 2006; Maestas et al. 2018).

Text Box 7.3 Treating channel incision in springs and meadows

Channel incision in headwater meadows and springs lowers the water table, drying out riparian and wetland vegetation. Many gullies begin at knickpoints, or headcuts, where enough flow concentrates to erode a pour-over hole and creating an abrupt change in elevation (a). Surface water runoff shifts from sheetflow above the headcut to concentrated flow below which accelerates runoff and erosion resulting in gully formation. Once started, headcuts migrate up valley until a hard point is reached. If headcuts are caught early, simple low-tech treatments can be implemented to protect and restore meadows and springs (Zeedyk and Clothier 2009). Hand-built structures made of natural materials installed at headcuts protect plant roots from further erosion while structures placed in downstream gullies slow flow, trap sediment, and raise water tables (b). These techniques have been used in a variety of rangeland settings, such as the desert southwest and Colorado’s Gunnison Basin where diverse partners are working to improve riparian resiliency and brood habitat for imperiled Gunnison sage-grouse (Centrocercus minimus, TNC 2017; Maestas et al. 2018; Silverman et al. 2018). Photo credits a–b: Shawn Conner, Jeremy Maestas.

5.2.4 Spring Development and Protection

Springs are interspersed throughout rangelands and play an important role in providing reliable water for livestock and habitat for wildlife, but they are prone also to degradation due to animal congregation, trampling, and improper grazing. Spring development to capture flow for stock water can also contribute to loss of riparian vegetation around springs. However, spring developments remain an essential practice to facilitate grazing management strategies to improve livestock distribution and overall rangeland health, including riparian goals. Thoughtful planning of water developments can protect ecological values while providing sufficient drinking water for livestock to enable effective grazing strategies such as grazing within a shorter duration and moving for recovery (Swanson et al. 2015). Gurrieri (2020) provides a review of considerations and sample designs for modern spring developments.

An overarching goal of spring developments should be to provide the needed livestock drinking water while returning as much as possible to the system and protecting riparian soils and vegetation. Removal of water from a spring impacts riparian hydrology and vegetation, so ideally livestock water should be sourced from the most productive and resilient sites possible. Where available, streams may be better alternatives for sourcing water than more fragile spring systems. Consulting a hydrologist about source flow rates and the amount needed to sustain the system is recommended. There are a variety of techniques that can be used in project design to minimize negative impacts on springs during development. For example, installing and maintaining a float valve on a trough allows the water to be automatically turned off when the trough is full and a shut-off valve allows trough water to be withdrawn from that area so all livestock move to the next trough and use area, leaving unneeded water in the spring system. Splitters can also be used to ensure that only a portion of water is diverted from the system. Adding pipelines and locating the trough away from the source concentrates trampling away from riparian soils and vegetation. Outdated, unused, or poorly maintained livestock water developments are abundant across western rangelands, but rehabilitation efforts can improve site conditions if the water source is intact or can be restored. Fencing spring sources (either using exclosures or pastures ) on new and old developments can help protect them from damage by grazing animals. Wildlife-friendly fence designs (Paige 2015), including virtual fencing where feasible (Campbell et al. 2018), should be considered to allow continued spring use by dependent wildlife. Long term maintenance is essential and should be included in project planning.

6 Summary

Historically, the importance of riparian areas and their connection to uplands has been overlooked or minimized in rangeland ecology and management. Wildlife biologists were among the first to raise awareness of the disproportionate value of riparian areas in sustaining biodiversity (Johnson and Jones 1977; Thomas et al. 1979). Habitat supplied by riparian areas, in the form of food, cover, water, refugia, and corridors, helps support unique aquatic and semi-aquatic species, as well as most terrestrial species found in rangelands. In recent decades, a growing body of science has shown how vital these ecosystems are for supplying a wide variety of goods and services, ranging from water quality and flood control to wildfire and drought resilience (NRC 2002; McKinstry et al. 2004; Silverman et al. 2018; Fairfax and Whittle 2020). Today, riparian ecology is rightfully recognized as an integral component of holistic rangeland management and is among the top resource issues being addressed by agencies and landowners across private and public rangelands (BLM 2021; NRCS 2021).

Enhancing the resilience of riparian areas will only become more essential for climate change mitigation and adaptation (Seavy et al. 2009; Capon et al. 2013; Reed et al. 2020). Increasing climate variability and extreme weather events make inhabiting already harsh rangeland environments more difficult for wildlife and people. Healthy riparian systems provide natural infrastructure to buffer against climate change effects and meet growing water demands. Because many western riparian areas have been degraded for so long (e.g., more than two centuries in some cases), a shifting baseline of riparian expectations under-represents what is possible (Wheaton et al. 2019a). With a current knowledge of ecology, hydrology, and geomorphology, rangeland conservationists are better equipped to implement management and restoration strategies necessary to realize the full riparian potential. Building riparian resiliency serves as a unifying goal to reduce vulnerability of rangeland wildlife and human communities in a changing world.