Consumptive Biological Uses
Consumptive biological uses such as improper grazing practices, logging, fuel wood collection, and deforestation have the potential to affect SGCN and their habitats throughout New Mexico. Where multiple consumptive biological uses occur (e.g. national forests), concerns persist regarding the ability to maintain habitats in the condition, connectivity, and quantity necessary to sustain viable and resilient populations of resident SGCN. Whether or not national forests can host a variety of land uses without heightened resource conflicts is a serious question.
Domestic animal grazing is an extensive land use activity across the New Mexico land surface (See Chapter 3, New Mexico's Biodiversity). Thus, it has significant association with factors that widely influence condition of wildlife habitat. Discussion here and elsewhere in the CWCS acknowledges this pattern while also recognizing that livestock operations are a permissible and important part of the New Mexico culture and economy.
Improper grazing practices have influenced vegetation communities and fish and wildlife habitat throughout New Mexico. Improper grazing practices are those practices that reduce long-term plant and animal productivity (Wilson and MacLeod 1991), and include both domestic livestock and wildlife. Major changes in vegetation composition in New Mexico and the southwest have been linked to improper livestock grazing that occurred in the late 1800s when livestock numbers peaked (Leopold 1924, Cottam and Stewart 1940, Cooper 1960, Buffington and Herbel 1965, Humphrey 1987, Grover and Musick 1990, Archer 1994, Fleischner 1994, Pieper 1994). Preferred forage plants such as cool-season grasses declined, while weedy and unpalatable plants and shrubs increased (Wooton 1908, Bohrer 1975, Bahre and Shelton 1993). Improper grazing practices and climatic fluctuations were recognized as major triggers of soil erosion, flooding, and arroyo cutting in the southwest (Cooperrider and Hendricks 1937, Cottam and Stewart 1940, Smith 1953, Hastings and Turner 1965, Cooke and Reeves 1976, Branson 1985, Humphrey 1987, Bahre 1991, Webb and Betancourt 1992, Felger and Wilson 1995). These acts reduced and/or eliminated fine herbaceous fuels which practically eliminated high-frequency, low-intensity wildfires across New Mexico and the southwest (Savage and Swetnam 1990, Swetnam 1990, Swetnam and Baisan 1996). All of these acts perpetuated further landscape degradation. By the 1930's, Congress recognized that western rangelands were being degraded, and approved the Taylor Grazing Act of 1934. This act regulated grazing on the public lands through the use of permits. The Taylor Grazing Act provided a way to regulate the occupancy and use of the public land, preserve the land from destruction or unnecessary injury, and provide for orderly use, improvement, and development. The Federal Land Policy and Management Act of 1976 and the Public Rangelands Improvement Act of 1978 further guide the management of livestock grazing on public lands and are designed to speed restoration of public rangelands while improving the delivery of services to public land users.
Outcomes of improper grazing practices on wildlife include increased competition for limited water, forage, and space, alteration of vegetative composition and structure, impacts on stream hydrology and water quality, and reduced soil permeability and potential to support plants due to soil compaction (Armour et al. 1994, Fleischner 1994, The Wildlife Society 1996, Belsky and Blumenthal 1997). More informed grazing practices have been implemented on many private and public land tracts in recent years, but recovery of vegetation may take many years and is not possible on some sites.
It is important to remember that the impact of livestock grazing on rangeland wildlife is largely dependent on the grazing management practices used (Holechek et al. 2004). Broad generalizations on the impact of livestock grazing on rangeland wildlife are typically incorrect because different grazing practices are unique and wildlife species have different habitat requirements. Grazing management variables that affect wildlife habitat include stocking rates, stocking density, the age and physiological condition of cattle, grazing season, forage selection, and cattle distribution. In addition, factors such as range condition, soil type, temperature, and precipitation also greatly influence the relationships between grazing and habitat quality for rangeland wildlife (Holechek et al. 2004). Grazing plans, therefore, need to be site-specific and consider the habitat needs of the wildlife species of interest.
Over the last couple of decades, there has been considerable research on interactions between rangeland wildlife and livestock, including comprehensive reviews by Holechek et al. (1982), Kie et al. (1994), Krausman (1996), Sarr (2002), and Holechek et al. (2004). Unfortunately, many of these scientific studies have been observational, anecdotal, based on unreplicated experiments, compromised by lack of true controls, employed weak methodologies, and used inaccurate or overly broad quantification of grazing intensity such as heavy vs. light or no grazing (Holechek et al. 2004, Lucas et al. 2004).
Holechek et al. (1982), Kirby et al. (1992), Launchbaugh et al. (1996), and Holechek et al. (2001) indicate that judicious grazing practices can have positive affects on wildlife and be a beneficial management tool. These include: 1) increase in vegetation composition diversity and improve forage availability and quality for early to mid-successional wildlife species, 2) creating patchy habitat with high structural diversity for feeding, nesting, and hiding, 3) opening up areas of dense vegetation to improve foraging areas for a variety of wildlife, 4) removal of rank, coarse grass that will encourage re-growth and improve abundances of high quality forages for wild ungulates, 5) stimulating browse production by reducing grass biomass, and 6) improving nutritional quality of browse by stimulating plant re-growth. There are a few examples in the literature which suggest that many wildlife species are tolerant of moderate grazing and many appear to benefit from light to conservative grazing. Smith et al. (1996) found that lightly grazed climax rangelands and conservatively grazed late seral rangelands had similar songbird and total bird populations. Smith et al. (1996) concluded that wildlife diversity was higher on the conservatively grazed late seral than the lightly grazed climax rangeland. Similarly, Nelson et al. (1997) reported that wildlife observations were greater on moderately grazed mid seral Chihuahuan Desert rangelands compared to conservatively grazed late seral rangelands. In a study comparing wildlife observations for grassland (late seral), shrub-grass (mid seral), and shrubland (early seral) communities in the Chihuahuan Desert of New Mexico, Nelson et al. (1999) found observations for birds and mammals were higher in shrub-grass than in grassland or shrubland. Studies in southeastern Arizona by Bock et al. (1984) support the hypothesis that conservatively to moderately grazed areas in mid or late seral condition supported greater diversity of wildlife than ungrazed areas in climax condition. However, these studies did not investigate livestock grazing intensity on wildlife population dynamics, or habitat requirements.
There has also been research directed towards evaluating managed livestock grazing systems on targeted wildlife species, especially with upland gamebirds and large mammals. For example, Montezuma quail (Cyrtonyx montezumae) are sensitive to livestock grazing and require adequate residual bunchgrass cover following the growing season for nest and escape habitat. Research suggests that Montezuma quail require a minimum of 7.8 in (20 cm) height of bunchgrasses and at least 50% herbaceous cover (Bristow and Ockenfels 2003). Grazing practices that employ light to moderate grazing can benefit Montezuma quail by increasing availability of food plants (Brown 1982, Bristow and Ockenfels 2000). Other studies on scaled quail (Callipepla squamata) indicated that they can be benefited by conservative to moderate grazing (on non-degraded rangelands) which improves their mobility by opening dense grass stands (Campbell et al. 1973, Saiwana et al. 1998). Livestock grazing can be used to enhance forage for elk (Cervus elaphus) and manage their distribution by increasing availability and nutritional value of preferred grasses in early growth stages (Holechek et al. 2004).
Scientific studies that clearly demonstrate a cause and effect relationship with grazing as the primary factor endangering a specific species are rare (Holechek et al. 2004). This is largely because studies that are specifically designed to detect these relationships are difficult to conduct in natural environments. Although there is certainly strong circumstantial evidence that heavy grazing can be a major factor resulting in the decline of several endangered rangeland wildlife species, carefully controlled studies are needed to better examine and understand the relationships between controlled grazing (i.e. light, conservative, and moderate grazing intensity) and endangered species (Sarr 2002, Holechek et al. 2004, Lucas et al. 2004).
Extraction of timber products is an important economic pursuit, but can have adverse effects on wildlife if not implemented wisely and responsibly. Over the last century, species composition and structure of New Mexico's forests have been altered by the combined effects of commercial logging, fire suppression, and improper grazing practices (US Forest Service 1993, Covington and Moore 1994). Logging practices in New Mexico and the Southwest have gone through differing management phases. In the late 1800s and early 1900s relatively indiscriminate cutting practices occurred (deBuys 1985), followed by selective logging in the mid-1900s, and even-aged timber stand management during the 1960s through 1980s (Bogan et al. 1998). Extensive road networks were developed within the forests to allow easy timber removal (Allen 1989).
Earlier logging practices tended to remove larger, older trees. More recently, logging techniques have moved toward more selective, uneven-aged silvicultural practices. Timber harvests from public forests have declined in recent years (Bogan et al. 1998). Some emphasis has been placed on federal endangered species habitat and ecosystem management. This has come about primarily through legal actions advanced under the Endangered Species Act, National Forest Management Act, and National Environmental Policy Act. Relatively recent Forest Service Region 3 directives require the maintenance of at least some old-growth forests for SGCN, such as the northern goshawk (Accipiter gentilis) and Mexican spotted owl (Strix occidentalis lucida). Fuel reduction is a focus of current forest management efforts, with millions of dollars directed at thinning understory trees and the reintroduction of prescribed fires to reduce the potential for widespread catastrophic wildfires (Bogan et al. 1998). Indications are that 50% of the allocated monies will be expended on protecting human structures and neighborhoods in the wildland urban interface areas.
Fuel Wood Collection
Fuel wood collection has reduced the abundance of large diameter snags and dead-and-down logs. Large diameter snags function as important nesting structures for cavity-nesting birds (Thomas et al. 1979, Hejl 1994) and as roost sites for bat species (Bogan et al. 1998). Dead-and-down logs provide important wildlife habitat and ecosystem functions. Legal and illegal roads created for access to fuel wood can further fragment forests and woodlands and adversely affect important habitats, such as wetlands and meadows, by transporting non-native organisms and draining wetlands. Fuel wood collection may also introduce disturbances from noise, off-road vehicle use, or accidental fire ignition.