Lower Sonoran Desertscrub
Lower Sonoran desertscrub is the most arid habitat found in Arizona. The vegetation community is dominated by drought-tolerant, low, open stands of creosote bush and white bursage. Winter annuals make up the bulk of the remainder of the vegetation and their blooms can be surprisingly colorful in wet years. Columnar cacti, ocotillo, and cholla, although present, are less abundant than in the neighboring Upland Sonoran desertscrub. Larger trees, such as ironwood, palo verde, and mesquite are largely confined to washes and other drainages (Brown et al. 2017).
The basin and range landscape is typically comprises of broad, relatively flat valleys separated by scattered, small mountain ranges (Dimmitt 2015). These xeric mountain ranges provide habitat for desert bighorn sheep and Sonoran desert tortoises. Stabilized and active dunes are present throughout this habitat which support a variety of dune and sand-specialist species of plants and animals such as ajo lilies, desert sandfood, flat-tailed and Goode’s horned lizards, Yuman desert and Mojave fringe-toed lizards, and sidewinders. LeConte’s thrasher, round-tailed ground squirrel, desert kangaroo rat, and kit fox are also present in this habitat type (Turner 1994).
The lower reaches of the Colorado and Gila rivers flow through this dry desert region providing a variety of important aquatic and riparian habitats for many fish and wildlife species. Additionally, these riparian areas provide water for agricultural and municipal uses. At least 21% of this habitat type has been lost due to development and agriculture. Approximately 45% of lower Sonoran desertscrub is federal land, including Barry M. Goldwater Range, Yuma Proving Ground, and Cabeza Prieta and KOFA National Wildlife Refuges. Because of this ownership, opportunities may exist to protect and restore large tracts of land in this region.
Significant Habitat Features
The following describes habitat features or microhabitats that are unique to this habitat type and are of particular importance to certain species:
Riparian areas, such as the Gila, Bill Williams, and Colorado Rivers, are important for wildlife and support the only cottonwood and willow forest in lower Sonoran desertscrub. This riparian forest and associated marshlands provide critically important habitat for a variety of species, including Yuma Ridgway’s rail, California black rail, southwestern willow flycatcher, western yellow-billed cuckoo, and northern Mexican gartersnake. Additionally, these river systems provide some of the only perennial water found in these hyper-arid areas.
Stabilized and active dune systems are unique to lower Sonoran desertscrub habitat in Arizona. These sandy areas provide habitat for a variety of sand-specialized species such as several desert fringe-toed lizard species, flat-tailed horned lizards, Mojave and resplendent shovel-nosed snakes, sidewinders, and desert kangaroo rats. A variety of dune and sand specialist plants can also be found in these areas, including ajo lily, scaly-stemmed sand plant, sandfood, Gander’s cryptantha, tansy spectaclepod, desert twinbugs, saw-toothed ditaxis, galleta grass, Emoryi’s indigobush, Schott’s wire-lettuce, and fanleaf crinklemat (Felger et al. 2003).
Ephemeral washes and pools are important breeding habitats for a variety of desert anurans, including Sonoran green toad, Sinaloan narrow-mouthed toad, lowland burrowing treefrog, and Sonoran desert toad (Brennen and Holycross 2009). Washes, despite their ephemeral nature, support higher densities of mesquite and ironwood compared to the surrounding plains. These linear woodlands serve as nesting sites for birds, provide browse and cover for ungulates, and act as movement corridors for a variety of wildlife species.
Bedrock tinajas are small rain-filled pools that develop in bedrock depressions created by wind and water erosion found in the Cabeza Prieta, Gila, Kofa, and Tinajas Altas mountains. These features collect water during rare periods of rain and are vital sources of water for desert bighorn sheep and other montane species.
Bajadas are the coalescence of alluvial fans along a mountain front where fine sediment is deposited at the end of dry washes and other drainages. Because of this soil composition, these slopes can host a greater diversity of vegetation and more complex vertical structure compared to surrounding areas.
Saguaro cacti are a keystone species in the Sonoran desert, providing a variety of resources for desert fauna. Saguaros provide nectar, pollen, and fruit for two species of SGCN nectivorous bats, as well as a host of other pollinator species that occur across much of southern Arizona. Saguaros also provide cavities for nesting avian species such as cactus ferruginous pygmy owl and western screech owl. Invasive buffelgrass — which outcompetes native flora and provides fuel for wildfire — is a major threat to these iconic keystone species.
The following list represents SGCN in this habitat type that AZGFD actively manages or are watching closely due to some level of concern:
Sonoran Green Toad, Sinaloan Narrow-mouthed Toad, Lowland Burrowing Treefrog, Sonoran Desert Toad
Costa's Hummingbird, LeConte's Thrasher, Bendire's Thrasher, Verdin, Western Screech-Owl, Bald Eagle, Golden Eagle, Loggerhead Shrike, California Black Rail, Southwestern Willow Flycatcher, Ridgway's Rail, Western Yellow-billed Cuckoo
Phoenix (Squaw Peak) Talussnail, Eastern Desertsnail
Sonoran Pronghorn, Harris's Antelope Squirrel, Antelope Jackrabbit, California Leaf-nosed Bat, Lesser Long-nosed Bat, Mexican Free-tailed Bat, Western Red Bat, Greater Western Mastiff Bat, Pocketed Free-tailed Bat
Goode's Horned Lizard, Flat-tailed Horned Lizard, Yuman Desert Fringe-toed Lizard, Mohave Fringe-toed Lizard, Mohawk Dunes Fringe-toed Lizard, Sonoran Collared Lizard, Speckled Rattlesnake, Sonoran Coralsnake, Three-lined Boa, Sonoran Desert Tortoise, Arizona Mud Turtle, Gila Monster
Sensitive Plant Species
The following list represents plant species that are known to occur in this habitat type:scaly sandplant, sandfood
Additional Influential Species
The following are other wildlife species, native and non-native, that can have particular influence in this habitat type. Influential species can affect SGCN and their habitats directly and indirectly, for example altering predator/prey interactions, overgrazing, outcompeting natives, creating microhabitats, and others.
Black-tailed Gnatcatcher, Lesser Nighthawk, Gambel's Quail, Mourning Dove, White-winged Dove
Stinknet, Giant Salvinia, Tamarisk, Sahara Mustard
Desert Bighorn Sheep, Mule Deer, Desert Cottontail, Pallid Bat, Western Yellow Bat, Cave Myotis, Canyon Bat
Desert Iguana, Sidewinder, Common Chuckwalla, Resplendent Shovel-nosed Snake, Mohave Rattlesnake
The following describes the primary threats facing this habitat type, adapted from Salafsky et al. (2008). First-level threats (i.e. Agriculture, Climate Change) represent broad categories while second-level threats reflect more specific stressors to the system. For detailed information on threats to this habitat type and conservation actions being taken, see Chapter 8: Threats and Conservation Actions.
2. Biological Resource Use
3. Climate Change and Severe Weather
4. Residential and Commercial Development
5. Disease, Pathogens, and Parasites
6. Energy Production and Mining
7. Human Intrusions and Disturbance
8. Invasive and Other Problematic Species
9. Natural System Modifications
11. Transportation and Service Corridors
The following describes specific conservation actions that can be taken to reduce or eliminate threats to this habitat type, adapted from Salafsky et al. (2008). Level 1 conservation actions (i.e. Land and Water Protection) represent broad categories of potential actions, while the Level 2 conservation actions (i.e. Resource and habitat protection) are more specific.
1. Land and Water Protection
- Identify wildlife corridors essential to the movement of species between high-quality habitat blocks. (Threats 4.1, 4.2)
- Engage communities to incorporate natural resource values and open spaces into long-term planning. Acquire land and water rights, pursue conservation agreements and easements, especially in critical wildlife corridors. (Threats 4.1, 4.3, 6.2, 6.3, 7.1)
- Continue maintenance of wildlife waters to mitigate drought and the effects of temperature extremes. (Threats 3.2, 3.3)
2. Land and Water Management
- Implement projects focused on improving the quality of altered systems creating suitable habitat and/or habitat features for wildlife. Actively seek opportunities to partner with Arizona agricultural producers, private landowners, and land management agencies on a variety of habitat enhancements that benefit both livestock and wildlife. (Threats 1.1, 1.3, 3.1, 4.1, 4.2, 4.3, 6.2, 6.3, 7.1, 7.2, 9.1)
- Continue disease monitoring efforts for impacted species. Avoid inadvertent spread of disease by following the proper disinfectant protocols. (Threat 5)
- Conduct monitoring and targeted removal efforts to limit establishment and spread of invasive species, especially in COAs or other important wildlife areas. Continue removal activities for trespass livestock, burros, and feral horses on managed lands. (Threats 1.3, 8.1, 9.1)
4. Education and Awareness
- Engage communities to incorporate natural resource values and open spaces into long-term planning. (Threats 1.1, 1.3, 4.1, 4.2, 4.3, 6.3, 7.1, 10.1, 10.2, 10.3, 10.4, 11.1)
- Conduct emerging disease education and outreach to user groups who potentially come into contact with affected species. Provide education on methods for avoiding the spread of diseases, pathogens, and parasites into novel populations of wildlife (i.e. bats and white-nose syndrome). (Threat 5)
- Provide extensive educational outreach through public events, social media messaging, billboards, and partnering with AZ State Parks, OHV dealers, OHV rental companies as well as off-road clubs and organizations. Educate new outdoor enthusiasts on safe, ethical practices and proper behavior in natural settings and in proximity to wildlife. (Threats 4.3, 7.1, 11.1)
- Work with developers, federal permitting agencies, the Arizona Corporation Commission (ACC), and state and local governments to raise awareness of impacts to wildlife and habitat from renewable and nonrenewable energy development. (Threats 6.3, 11.2)
- Develop outreach programs for the public on impacts to wildlife, agriculture, and recreation from introduced species. Incorporate citizen science programs to identify distribution of invasives (such as iMapInvasives.org). (Threat 8.1)
5. Law and Policy
- Conduct statewide law enforcement patrols targeting illegal OHV use as well as targeted saturation patrols in areas identified as critical habitat that are being adversely impacted by OHV and other recreational activities. (Threat 7.1)
- Inform federal and state agencies of critical need for wildlife movement across the international border with Mexico, and help design any necessary border barriers to allow wildlife movement. (Threat 7.2)
- Conduct statewide law enforcement patrols targeting illegal take of wildlife, especially during scheduled hunts. (Threat 2.1)
6. Livelihood, Economic and Other Incentives
- Collaborate with the development and renewable energy industries to incorporate BMPs and other measures to reduce impacts to wildlife and habitats. Identify ways for incentivizing incorporation of recommendations. (Threats 4.1, 4.2, 6.3)
- Work with local governments to incorporate wildlife protections and habitat connectivity into general plans. (Threats 4.1, 4.2, 6.3)
- Share information and discuss the benefits of participating in species recovery programs such as Safe Harbor Agreements, Habitat Conservation Plans, Candidate Conservation Agreements with Assurances, and Candidate Conservation Agreements with interested landowners. (Threats 1.1, 3.1, 1.3, 7.1)
7. External Capacity Building
- Collaborate with partners across different geographies (e.g., statewide, regional, national and international) to develop and implement management plans, conservation agreements, recovery actions, research, management recommendations, and to determine the effectiveness of specific management efforts for long-term conservation of SCGN wildlife. (Threats 3.1, 3.2, 3.3, 3.4, 5, 8.1)
Conservation in the Context of Climate Change
The following describes some of the conservation strategies that may mitigate the effects of a changing climate for this habitat type. Strategies have been adapted from guidelines by the Association of Fish and Wildlife Agencies (AFWA 2009).
Encourage and facilitate strategic planning for the renewable energy industry.
Identify and improve the connectivity of natural landscapes to better link wildlife populations and allow for range shifts.
Identify populations that could benefit from assisted migrations and/or translocation.
Implement long-term monitoring protocols for vulnerable species and habitats to inform adaptive management.
Establish new wild and/or captive populations of climate-vulnerable SGCN.
Maintain existing and identify new wildlife waters for drought mitigation.
Monitor and mitigate for introduced/invasive species.
Other Conservation Actions
The following describe other routine or on-going conservation actions AZGFD regularly performs in this habitat type:
- Conduct surveys and monitor populations of SGCN as specified in work plans and job statements.
- Implement conservation actions to promote populations of SGCN species.
- Collect specimens or samples for taxonomic analysis, genetics, research, and/or disease testing.
- Fund or work with partners to conduct conservation-related species research.
- Manage recreational activities and OHV use of desertscrub habitat to minimize negative impacts to habitat and associated species.
Conservation Opportunity Areas (COAs)
The following represents identified COAs where conservation efforts would benefit wildlife and their habitats.
- Bouse Dunes
- Colorado River Nature Center Wildlife Area
- Desert Mountains Complex
- Estrella Maricopa Corridor
- Harquahala Plain
- King Valley
- Lower Salt and Gila Rivers
- Mittry Lake Wildlife Area
- Palomas Plain
- Phoenix Area Snails
- Ranegras Plain
- Vekol Valley
- Yuma Desert
The following is a list of the organizations and agencies that AZGFD regularly partners with on conservation efforts in this habitat type:
- Department of Defense Yuma Proving Ground
- Department of Defense - Barry M. Goldwater Range
- DOD U.S. Marine Corps
- DOD Air Force
- USFWS Kofa National Wildlife Refuge
- USFWS Cabeza Prieta National Wildlife Refuge
- USFWS Imperial National Wildlife Refuge
- USFWS Cibola National Wildlife Refuge
- USFWS Arizona Ecological Services
- Sonoran Desert National Monument
- US Bureau of Reclamation
- Bureau of Land Management
- Gila River Indian Community
- Ak-Chin Indian Community
- Colorado River Indian Tribes
- Arizona-Sonora Desert Museum
- Arizona Center for Nature Conservation-Phoenix Zoo
- Desert Botanical Garden
- Lower Colorado River Multi-Species Conservation Program
- Yuma Crossing National Heritage Area
- Maricopa County Parks
- Pinal County Open Space and Trails
- Pima County Office of Conservation and Sustainability
- City of Phoenix Parks and Recreation
- City of Glendale Parks and Recreation
- Audubon Arizona
- AZ Department of Transportation
- US Army Corps of Engineers
- City of Buckeye
- City of Avondale
- Town of Marana
- US Geological Survey
- Gila Bend
- Natural Resources Conservation Service
- Maricopa County Flood Control District
- Arizona State University
- University of Arizona
- Sonoran Joint Venture
- Arizona Field Ornithologists
- Arizona Monarch Collaborative
- Southwest Monarch Study
- Gila Watershed Partnership
Important Conservation Resources
The following are relevant conservation agreements, plans, and other documents or particular interest regarding wildlife in this habitat type:
- Flat-tailed Horned Lizard Rangewide Management Strategy
- Sonoran Pronghorn Recovery Plan
- Lower Colorado River Multi-Species Conservation Program
- Candidate Conservation Agreement for Sonoran Desert Tortoise
- Western Burrowing Owl Clearance Protocol
- MOU Between BLM and USFWS for Conservation of Migratory Birds
- Pima County Multi-Species Conservation Plan
- Lesser Long-nosed Bat Status Assessment
- Arizona Partners in Flight Bird Conservation Plan
- Arizona Bat Conservation Strategic Plan
- Western Monarch Butterfly Conservation Plan