Non-consumptive recreational activities, military exercises, and the international border are just a few of the ways that human activities can disrupt wildlife and alter their habitat. Although seemingly innocuous, even low- or no-impact activities can negatively affect wildlife by altering behaviors. Responses are varied depending on the sensitivity of the species and the duration, timing, and intensity of disturbance, and may include increased alertness, heightened stress-hormone levels and, in some cases, a decrease in survival and/or reproduction or even abandonment of an area (Bötsch et al. 2017).
It can be hard to accept that the recreational activities we are so passionate about, such as hiking, biking, horseback riding, off-road vehicle use, camping, and water sports, may negatively impact wildlife. However, the disturbance created and footprint left behind can degrade habitat, alter wildlife behavior, and even cause direct mortality. Simple practices like staying on designated roads and trails and following Leave No Trace guidelines can reduce this potential.
The attraction of Arizona’s unique waterways consistently results in some of the highest densities of recreational boating in the country. Additionally, boaters have access to some high-quality wildlife riparian, reservoir, and riverine areas. These outstanding recreational opportunities introduce additional challenges for species that depend on aquatic and riparian habitats. Motorized watercraft discharge chemicals that reduce water quality, while both motorized and non-motorized watercraft are potential vectors for aquatic invasive species transportation and introduction. Both water-based and terrestrial recreation within riparian areas, especially during bird nesting and breeding season, can affect foraging behavior, cause repeated flushing of birds, and lead to nest abandonment for raptors, some species of waterfowl, and other riparian birds. (Boyle et al. 1985; Knight and Cole 1995).
Off-Highway Vehicle (OHV) Use
Off-highway vehicle use is an increasingly popular recreational activity in Arizona. A 2020 University of Arizona study found that an estimated 24.4% of adult Arizonans engage in OHV use annually (Duval et al. 2020). A similar study conducted by Arizona State University in 2016-2017 found that residents and visitors spend approximately $1.8 billion dollars on OHV recreation in Arizona annually. While the socioeconomic importance of OHV recreation cannot be underestimated, it is also important to consider the impacts this activity has on the landscape and wildlife.
Paved, high-use roadways can fragment habitat, damage vegetation, increase erosion, and reduce connectivity. However, rural dirt roads and non-motorized trails can also result in similar negative impacts to wildlife and their habitats. OHV use can have a variety of direct and indirect effects on wildlife, with negative effects at the individual and population level. For example, high noise levels and increased human presence can trigger stress responses and lead to altered behavior or habitat use. In Arizona, the density of dirt roads was found to negatively influence space use by kit foxes (Jones et al. 2017). Direct mortality can result from vehicle-animal collisions, and animal injuries such as inner ear bleeding and hearing loss have been documented (Ouren et al. 2007). Indirect effects include collapsed burrows, degraded forage resources, or abandonment of key habitat or resources (Ouren et al. 2007), all of which can negatively affect population viability.
Popular off-roading areas like sand dunes and desert washes are important habitat for many reptile species including SGCN like the Yuman Desert, Mohave, and Mohawk Dunes fringe-toed lizards, flat-tailed horned lizard, Sonoran desert tortoise, and Mohave shovel-nosed snake. These areas are also home to more common small mammals like the banner-tailed, desert, and Merriam’s kangaroo rats and the Arizona and desert pocket mice. Negative effects to these species can also have consequences for their natural predators. The high level of traffic and noise, degraded vegetation, and the fragmentation caused by increased road and trail densities are therefore serious management concerns.
In higher-elevation areas that receive more moisture, heavy off-road vehicle traffic can result in soil compaction, erosion, increased sedimentation, and altered hydrological patterns. Ground disturbance can also promote invasion of non-native plant species. While the movement of some species is relatively unimpeded by gravel roads or dirt routes, other wildlife, such as some small mammals and amphibians, may perceive this as a barrier to movement (Ouren et al. 2007).
Staying on designated roads and trails or in special-use areas, and limiting travel near or through riparian areas and meadows, can reduce impacts to species and habitats. However, the best outcomes overall may result from improved communication and cooperation between OHV groups, land management agencies, and natural resource managers. A greater understanding of the issues and mutual respect could lead to improved recreational opportunities and less damage to important wildlife habitat.
Arizona’s military facilities span large areas, especially in the southern portion of the state. Military activities include research, development, testing, and evaluation of weapon and space systems, subsystems, and components. Other regular activities include live bombing, air defense missile firing, mechanized brigade training exercises, battalion-size or smaller training exercises, landings and training courses, maintenance of fighter wing capabilities, and other general military training exercises. While many of these activities pose a threat to wildlife due to disturbance and habitat degradation, the facilities work to limit negative impacts through Integrated Natural Resources Management Plans that outline the significant natural resources on the landscape and define goals and objectives to ensure compatible use between the military mission and natural resource management. Military lands such as Barry M. Goldwater, Yuma Proving Ground, Fort Huachuca, and Luke Air Force Base offer high quality habitat and refuge for species such as the federally endangered Sonoran pronghorn, the Sonoran desert tortoise, and the rare flat-tailed horned lizard, all species that have lost important portions of their historical ranges to development.
For decades, AZGFD has worked closely with our partners at the Department of Defense (DOD) to help manage, monitor, and protect wildlife and habitats at several military installations around the state. Meanwhile, the Sentinel Landscapes Partnership is a national program that brings together federal agencies, state and local governments, non-governmental organizations, and private landowners in an effort to advance sustainable land use while protecting defense facilities from incompatible development of adjacent lands. The partnership connects private landowners with voluntary state and federal assistance programs to maintain and enhance natural and working lands. In 2015, more than 62,000 acres surrounding Fort Huachuca were designated as a sentinel landscape with the goals of addressing water conservation issues, improving agricultural viability, restoring wildlife habitat, and protecting the military mission.
Arizona shares more than 350 miles of border with Mexico. Many wildlife species must move across this border on a daily, seasonal, or annual basis to obtain necessary resources such as food, cover, and water. AZGFD works closely with Mexican authorities and other partners through various committees, teams, and workgroups to ensure the continued conservation of many borderland species. However, the volume of illegal immigration, drug smuggling, and law enforcement activity along the border has increased dramatically in recent years, resulting in negative impacts to borderland habitats. The border wall creates an impenetrable barrier to wildlife movement that may have significant impacts on several rare and imperiled species including the Mexican wolf, jaguar, ocelot, Sonoran pronghorn, as well as more common species like mountain lion and black bear (Flesch et al. 2009).
Dispersed camping, altered fire regimes, decreased water quality from pollutants, unauthorized roads and trails, illegal dumping and littering, increased poaching, and illegal collecting of wildlife also threaten plant and animal life in this region. In addition, although law enforcement activities are necessary, they often create a damaging network of two-track routes across the desert landscape (Whitbeck and Fehmi 2016). Significant increases in the human population along the Arizona-Mexico border result in changes to land use, dewatering of aquatic systems, and increased pollution (Updike et al. 2013). Cumulative effects from these stressors are resulting in habitat loss and fragmentation, introduction and spread of invasive species, increases in wildlife disease, and increased wildlife mortality.
While it is difficult to attribute changes in wildlife behavior, distribution, and habitat use to a specific cause, it is apparent that certain species are highly sensitive to the human disturbances discussed here. Factors such as colonial behavior, unique breeding patterns, limited distribution, or narrow habitat requirements increase vulnerability to these stressors (Boyle and Samson 1985).