Sonoran Desert Conservation References

Welcome to FRIENDS OF THE SONORAN DESERT’S compilation of current peer-reviewed literature on Sonoran Desert conservation. FSD created this reference list for the conservation community and general public, to help protect the Sonoran Desert. Please share it widely.

Main headings and subheadings are alphabetized. Within headings, papers are listed by date, with the most recent citations listed first. To access the complete reference, either click on the underlined DOI number or copy and paste the title of the paper into your browser. In some cases, the journal will require payment for access to the complete reference, but abstracts should be available without charge.

We will update the reference list twice a year. Although there is no fee to use this resource, a donation to help us maintain it would be much appreciated.

Artificial Barriers: Walls, Fences, Canals, Roads and Artificial Lighting at Night

Canals, Fences, Roads, Walls

McInturff, A., W. Xu, C.E. Wilkinson, et al. 2020. Fence ecology: Frameworks for understanding the ecological effects of fences. BioScience [advance online] https://doi.org/10.1093/biosci/biaa103

KEY FINDING: Review article. The ecological effects of fences are reviewed. Fence densities in the western U.S. are estimated, and ecological winners and losers produced by fences are discussed. Research trends suggest that fence effects have been underestimated.

Dean, W.R., C.L. Seymour, G.S. Joseph, et al. 2019. A review of the impacts of roads on wildlife in semi-arid regions. Diversity 11: Article 81. https://doi.org/10.3390/d11050081

KEY FINDING: Review article. Impacts of roads on biodiversity in semi-arid regions include mortality or injury through collision, interference of road noise with vocal communication, and interference of artificial light along roads with navigation.

Jakes, A.F., P.F. Jones, L.C. Paige, et al. 2018. A fence runs through it: A call for greater attention to the influence of fences on wildlife and ecosystems. Biological Conservation 277:310-318. https://doi.org/10.1016/j.biocon.2018.09.026

KEY FINDING: Review article. To better manage fence effects on wildlife and ecosystems, examination of all aspects of fence ecology is required. Global prevalence of fencing, fence function and design, and pros and cons of fencing relative to wildlife conservation are reviewed.

Fowler, N., T. Keitt, O. Schmidt, et al. 2018. Border wall: Bad for biodiversity. Frontiers in Ecology and the Environment 16:137-138.

KEY FINDING: Construction of a wall on the U.S. Mexico border will fragment, degrade and/or destroy habitats, creating a huge negative impact on wild species and ecosystems.

Peters, R. W., J. Ripple, C. Wolf, et al. 2018. Nature divided, scientists united: US–Mexico border wall threatens biodiversity and binational conservation. BioScience 68:740-743. https://doi.org/10.1093/biosci/biy063

KEY FINDING: Review article. The border wall bypasses environmental laws, harms wildlife populations by eliminating, degrading, and fragmenting habitats, and devalues conservation investment and scientific research. Signed by over 2500 scientists in a call for action.

Herrmann, H.W., K.M. Pozarowski, A. Ochoa, et al. 2017. An interstate highway affects gene flow in a top reptilian predator (Crotalus atrox) of the Sonoran Desert. Conservation Genetics 18:911-924. https://doi.org/10.1007/s10592-017-0936-8

KEY FINDING: Interstate I-10 has reduced gene flow in a population of the western diamond-backed rattlesnake in southern Arizona.

Ogden, L.E. 2017. Border walls and biodiversity: new barriers, new horizons. BioScience 67:498–505. https://doi.org/10.1093/biosci/bix044

KEY FINDING: Review article. Border barriers and the multitude of problems they cause for wildlife are identified and discussed.

Hamdan, A., and J.C. Stromberg. 2016. Changes in riparian plant communities due to a canal barrier traversing ephemeral stream channels in the Sonoran Desert. Journal of Arid Environments 125:1-7. https://doi.org/10.1016/j.jaridenv.2015.09.013

KEY FINDING: Riparian vegetation of ephemeral streams has changed over 35 years in response to construction of the CAP, a canal system that traverses hundreds of ephemeral streams in the Sonoran Desert. CAP has created wet areas that support dense vegetation.

Trouwborst, A., F. Fleurke, and J. Dubrulle. 2016. Border fences and their impacts on large carnivores, large herbivores and biodiversity: An international wildlife law perspective. Reciel 25:291–306. https://doi.org/10.1111/reel.12169

KEY FINDING: Review article. Impacts of border fences on wildlife around the world are analyzed from a law and policy perspective, focusing on international wildlife law. Relevant provisions from global and regional legal instruments are identified.

Seidler, R.G., R.A. Long, J. Berger, et al. 2015. Identifying impediments to long-distance mammal migrations. Conservation Biology 29:99-109. https://doi.org/10.1111/cobi.12376

KEY FINDING: Threats to long-distance migration of pronghorn due to fences and highways were assessed. Migrating pronghorn avoid dense developments of natural gas fields and high-traffic highways, and underutilize high-quality habitat at crossings with migration bottlenecks.

McCallum, J.W., J.M. Rowcliffe, and I.C. Cuthill. 2014. Conservation on international boundaries: The impact of security barriers on selected terrestrial mammals in four protected areas in Arizona, USA. PLOS One 9: Article e93679. https://doi.org/10.1371/journal.pone.0093679

KEY FINDING: Several thousand terrestrial protected areas (PAs) lie on international boundaries, and many boundaries now have anthropogenic barriers. Intermittent fencing impacts some native species, but does not successfully restrict the movement of humans.

Lasky, J.R., W. Jetz, and T.H. Keitt. 2011. Conservation biogeography of the US–Mexico border: A transcontinental risk assessment of barriers to animal dispersal. Diversity and Distributions 17:673 - 687. https://doi.org/10.1111/j.1472-4642.2011.00765.x

KEY FINDING: Intersection of current and future barriers along the U.S./Mexico border with the geographic ranges of 313 amphibian, reptile, and non‐volant mammal species showed highest risk to biodiversity in three border regions (California, Madrean archipelago, and Gulf coast).

Harrington, J.L., and M.R. Conover. 2010. Characteristics of ungulate behavior and mortality associated with wire fences. Wildlife Society Bulletin 34:1295-1395. https://digitalcommons.usu.edu/etd/6610

KEY FINDING: Mortalities of pronghorn, mule deer, and elk associated with wire fences along Colorado and Utah roads were analyzed. Highest mortality rates coincided with weaning of fawns. Lethality of different types of woven-wire fences was reviewed.

Flesch, A.D., C.W. Epps, J.W. Cain III, et al. 2010. Potential effects of the United States‐Mexico border fence on wildlife. Conservation Biology 24:171-181. https://doi.org/10.1111/j.1523-1739.2009.01277.x

KEY FINDING: Large vegetation gaps and tall fences may limit transboundary movements of ferruginous pygmy owls. Impermeable fencing will disrupt transboundary movement by desert bighorn sheep and isolate some populations on the Arizona side of the U.S./Mexico border.

Bear, D. 2009. Border wall: Broadest waiver of law in American history. Washington DC Center for International Environmental Law. http://bit.ly/2DB81nI

KEY FINDING: Position paper. The broadest waiver of law in American History was executed to expedite construction of a wall on the U.S./Mexico border.

Leu, M., S.E. Hanse, and S.T. Knick. 2008. The human footprint in the west: A large-scale analysis of anthropogenic impacts. Ecological Applications 18:1119-1139. https://doi.org/10.1890/07-0480.1

KEY FINDING: Anthropogenic features (urbanization, roads, and power lines) are increasing in western U.S. landscapes. Disproportional regional effects of the human footprint on western landscapes are a challenge to management of ecosystems and wildlife populations.

Cohn, J.P. 2007. The environmental impacts of a border fence. BioScience 57:96. https://doi.org/10.1641/B570116

KEY FINDING: Arizona park and refuge managers, wildlife biologists, and conservationists assert that a wall on the US–Mexican border will fragment the Sonoran Desert, damage plant and animal communities, and prevent movement of wildlife between the U.S. and Mexico.

Andrews, A. 1990. Fragmentation of habitat by roads and utility corridors: A review. Australian Zoologist 1990:130-141. https://doi.org/10.7882/AZ.1990.005

KEY FINDING: Review article. Ecological effects of roads and utility corridors (power lines, pipelines, canals, and railway lines) on undisturbed habitat and native wildlife include increased mortality, divided populations, and invasions of common species.

Artificial Lighting at Night

Ditmer, M.A., D.C. Stoner, C.D. Francis, et al. 2020. Artificial nightlight alters the predator–prey dynamics of an apex carnivore. Ecography 43:1-13. https://doi.org/10.1111/ecog.05251

KEY FINDING: Individual cougars and mule deer living in areas with less light exposure avoided illuminated areas, whereas deer living in the wildland–urban interface selected elevated light levels, because cougars were less likely to hunt them under these higher light levels.

Shier, D.M., A.K. Bird, and T.B. Wang. 2020. Effects of artificial light at night on the foraging behavior of an endangered nocturnal mammal. Environmental Pollution 263: Article 114566. https://doi.org/10.1016/j.envpol.2020.114566

KEY FINDING: Artificial light negatively impacts foraging decisions of endangered kangaroo rats. Understanding impacts of disturbance, like artificial light at night, is critical for at-risk

species.

Touzot, M., L. Teulier, T. Lengagne, et al. 2019. Artificial light at night disturbs the activity and energy allocation of the common toad during the breeding period. Conservation Physiology 7: Article coz002. https://doi.org/10.1093/conphys/coz002

KEY FINDING: This study suggests that artificial light at night strongly impacts the activity and energy metabolism of common toads, which may have a long-term negative effect on the fitness of common toad populations.

Cabrera-Cruz, S.A., J.A. Smolinsky, K.P. McCarthy, et al. 2019. Urban areas affect altitudes of nocturnally migrating birds. Journal of Animal Ecology 88:1873-1887. https://doi.org/10.1111/1365-2656.13075

KEY FINDING: Migrating birds generally flew higher over (lighter) urban areas compared to (darker) rural areas in spring, a complex finding for which they have no interpretation.

Horton, K.G., C. Nilsson, B.M. Van Doren, et al. 2019. Bright lights in the big cities: migratory birds’ exposure to artificial light. Frontiers in Ecology and the Environment 17:209-214. https://doi.org/10.1002/fee.2029

KEY FINDING: Over two decades of remote‐sensing data collected by weather surveillance radar and satellite‐based sensors was used to identify locations and times of year when the highest numbers of migrating birds are exposed to light pollution in the contiguous US.

Sanders, D., and K.J. Gaston. 2018. How ecological communities respond to artificial light at night. Journal of Experimental Zoology Part A: Ecological and Integrative Physiology 329:394–400. https://doi.org/10.1002/jez.2157

KEY FINDING: This is a general overview. Current knowledge about community responses to artificial lighting at night is summarized, and different pathways and their impact on ecosystem functioning and stability are discussed.

McLaren, J.D., J.J. Buler, T. Schreckengost, et al. 2018. Artificial light at night confounds broad‐scale habitat use by migrating birds. Ecology Letters 21:356-364. https://doi.org/10.1111/ele.12902

KEY FINDING: Artificial lights are of high conservation concern for migrating birds, which are attracted to artificial light while airborne, reducing their tendency to choose high-quality stopover sites, which is critical for successful migration.

Gaston, K.J., T.W. Davies, S. L. Nedelec, et al. 2017. Impacts of artificial light at night on biological timings. Annual Review of Ecology, Evolution, and Systematics 48:49–68. https://doi.org/10.1146/annurev-ecolsys-110316-022745

KEY FINDING: Review article. Evidence for impacts of artificial night lighting on biological timings is compelling. Artificial night lighting has a pervasive and marked impact on ecological systems, necessitating a widespread implementation of mitigation measures.

Van Doren, B.M., K.G. Horton, A.M. Dokter, et al. 2017. High-intensity urban light installation dramatically alters nocturnal bird migration. PNAS 114:11175-11180. https://doi.org/10.1073/pnas.1708574114

KEY FINDING: Illumination of the 9/11 Memorial’s “Tribute in Light” (New York) induced significant behavioral change in migrating birds that disappeared when the lights were off: high-density aggregation, decreased flight speed, circular flight paths, and frequent calling.

Bliss-Ketchum, L.L., C.E. de Rivera, B.C.Turner, et al. 2016. The effect of artificial light on wildlife use of a passage structure. Biological Conservation 199:25-28. https://doi.org/10.1016/j.biocon.2016.04.025

KEY FINDING: Columbia black-tailed deer and deer mice avoided a bridge under-road passage structure when lit, suggesting avoidance of the light. Artificial light may be reducing habitat connectivity for these species.

Robert, K.A., J.A. Lesku, J. Partecke, et al. 2015. Artificial light at night desynchronizes strictly seasonal reproduction in a wild mammal. Proceedings of the Royal Society B 282: Article 20151745 http://dx.doi.org/10.1098/rspb.2015.1745

KEY FINDING: Artificial light at night (ALAN) modifies nocturnal melatonin secretion and delays reproductive activation in a seasonally reproducing free-ranging mammal, the tammar wallaby. ALAN may desynchronize seasonal physiological processes in wildlife.

Minnaar, C., J.G. Boyles, I.A. Minnaar, et al. 2015. Stacking the odds: light pollution may shift the balance in an ancient predator–prey arms race. Journal of Applied Ecology 52:522–531.https://doi.org/10.1111/1365-2664.12381

KEY FINDING: The effects of light pollution were studied in a free‐living bat–insect community. Increase sin moth consumption resulted from decreased eared‐moth defensive behaviour that was induced by increased light levels.

Longcore, T., C. Rich, P. Mineau, et al. 2013. Avian mortality at communication towers in the United States and Canada: which species, how many, and where? Biological Conservation 158:410-419. https://doi.org/10.1016/j.biocon.2012.09.019

KEY FINDING: Millions of birds migrating to and from breeding grounds in the U.S. and Canada are killed in collisions with lighted towers and guy wires. Thirteen birds of conservation concern suffer annual mortality of 1–9% of their estimated total population.

Dominoni, D, M. Quetting, and J. Partecke. 2013. Artificial light at night advances avian reproductive physiology. Proceedings of the Royal Society B 280: Article 20123017. https://doi.org/10.1098/rspb.2012.3017

KEY FINDING: Captive city and forest blackbirds exposed to light at night developed their reproductive system up to one month earlier than normal and molted earlier than birds kept under dark nights, showing the impact of human-induced lighting on animal physiology.

Longcore, T., C. Rich, and S.A. Gauthreaux, Jr. 2008. Height, guy wires, and steady-burning lights increase hazard of communication towers to nocturnal migrants: a review and meta-analysis. Auk 125:486–493. https://doi.org/10.1525/auk.2008.06253

KEY FINDING: The lighting scheme of communication towers may be the most important factor controllable by humans that contributes to bird kills at towers. Use of strobe or flashing lights on towers results in less bird aggregation and lower bird mortality than use of steady-burning lights.

Lowery, S.F., S.T. Blackman, and D. Abbate. 2007. Urban Movement patterns of Lesser Long-nosed bats (Leptonycteris curasoae): management Implications for the Habitat Conservation Plan within the City of Tucson and the Town of Marana. Research Branch Arizona Game and Fish Department 5000 W. Carefree Highway Phoenix, AZ 85086. Pp. 1-22.

KEY FINDING: Light pollution should be limited along identified flight corridors of lesser long-nosed bats, which directly selecting for areas managed for lower light intensity.

Beier, P. 2006. Effects of artificial night lighting on terrestrial mammals. Pp. 19-42. In: Ecological Consequences of Artificial Night Lighting. C. Rich, and T. Longcore, editors. Island Press: Washington, D.C.

KEY FINDING: Book chapter. Excellent review of artificial night lighting on wild terrestrial mammals. Small nocturnal herbivores are at increased risk of predation and decrease food consumption. Light disrupts circadian rhythms and melatonin production in mammals.

Gauthreaux Jr., S.A., and C.G. Belser. 2006. Effects of artificial night lighting on migrating birds. Pp. 67-93. In: Ecological Consequences of Artificial Night Lighting. C. Rich, and T. Longcore, editors. Island Press: Washington, D.C.

KEY FINDING: Book chapter. Excellent review of effects of artificial night lighting on migrating birds. Migratory birds are attracted to artificial lights on communication towers. To reduce mortality of migrating birds, white strobe lights are preferable to red or constant lighting.

Buchanan, B.W. 2006. Observed and potential effects of artificial night lighting on anuran amphibians. Pp. 192-220. In: Ecological Consequences of Artificial Night Lighting. C. Rich, and T. Longcore, editors. Island Press: Washington, D.C.

KEY FINDING: Book chapter. Excellent review of effects of artificial night lighting on anuran amphibians. ANL may negatively affect reproductive behavior, anti-predator behavior, nocturnal activity, photoperiod, and development of eggs and larvae.

Cultural and Indigenous Issues

EagleWoman, A. 2009. Eagle and the condor of the western hemisphere: application of international indigenous principles to halt the United States border wall. Idaho Law Review 45: 1-18. https://ssrn.com/abstract=1440831

KEY FINDING: Review article. Interrelationship of indigenous peoples in the Western Hemisphere is discussed regarding expansion of the U.S./Mexico border wall, focusing on the impact of the wall on indigenous communities in the political border region.

Cronin, A.E., and D.M. Ostergren, 2007. Democracy, participation, and Native American tribes in collaborative watershed management. Society and Natural Resources 20:527–542. https://doi.org/10.1080/08941920701338059

KEY FINDING: The Yavapai-Apache Nation (YAN) of central Arizona have yet to receive their 1,300 acre-feet of unadjudicated water rights from the Central Arizona Project, which has led to distrust of collaborative endeavors with local communities on watershed management issues.

Sonoran Desert Animals

Amphibians

Allen, C., R. Gonzales, and L. Parrott. 2020. Modelling the contribution of ephemeral wetlands to landscape connectivity. Ecological Modelling 419: Article 108944. https://doi.org/10.1016/j.ecolmodel.2020.108944

KEY FINDING: A landscape approach to wetland conservation is essential for retaining viable amphibian populations in the context of human induced habitat loss and climate change.

Mims, M.C., C.E. Moore, and E.J. Shadle. 2020. Threats to aquatic taxa in an arid landscape: knowledge gaps and areas of understanding for amphibians of the American Southwest. Wiley Interdisciplinary Reviews-Water 7: Article e1449. https://doi.org/10.1002/wat2.1449

KEY FINDING: Review Article. A review of 81 publications and 341 species revealed well-covered threats: hydrological alteration and introduced species, changes to community dynamics, land use, and precipitation. Threats linked to climate change were less well-covered.

Kiesow, A.B., and K.L. Griffis-Kyle. 2017. Desert amphibian selection of arid land breeding habitat undermines reproductive effort. Oecologia 185:619-627. https://doi.org/10.1007/s00442-017-3969-2

KEY FINDING: Providing anthropogenic water sites without managing ammonia levels may cause long-term declines in desert anuran populations.

McIntyre, N.E., J.C. Drake, and K.L. Griffis-Kyle. 2016. A connectivity and wildlife management conflict in isolated desert waters. Journal of Wildlife Management 80:655-666. https://doi.org/10.1002/jwmg.1059

KEY FINDING: Artificial water catchments for large mammals in arid environments also increase connectivity between breeding sites for amphibians. High ammonia concentrations in these catchments may harm amphibian health, reproduction, and population persistence.

Griffis-Kyle, K.L. 2016. Physiology and ecology to inform climate adaptation strategies for desert amphibians. Herpetological Conservation and Biology 11:563-582. https://gato-docs.its.txstate.edu/jcr:c2aaf670-b71c-4094-aaad-ea02bb7b22fc/Paper%20-%20April%2017,%202020.pdf

KEY FINDING: Generalized management strategies for amphibians may not apply to anurans in temperate and subtropical deserts, who rely on rainfall sufficient to support reproduction.

Zylstra, E.R., R.J. Steidl, D.E. Swann, et al. 2015. Hydrologic variability governs population dynamics of a vulnerable amphibian in an arid environment. Plos One 10: Article e0125670.

https://doi.org/10.1371/journal.pone.0125670

KEY FINDING: 16 years of data from intermittent mountain streams in the Sonoran Desert showed that adult monthly survival and recruitment into adulthood of the lowland leopard frog increased with availability of surface water.

Birds

Flesch, A.D., R.L. Hutto, W.J.D. van Leeuwen, et al. 2015. Spatial, temporal, and density-dependent components of habitat quality for a desert owl. 2015. PLOS One 10: Article e0119986. https://doi.org/10.1371/journal.pone.0119986

KEY FINDING: Variation in reproductive output in ferruginous pygmy owls was greater across space than time. Habitat resources explained more of the variation than weather or conspecifics, but interactions among these components were strong.

Villarreal, M.L., C. van Riper III, and R.E. Petrakis. 2014. Conflation and aggregation of spatial data improve predictive models for species with limited habitats: A case of the threatened yellow-billed cuckoo in Arizona, USA. Applied Geography 47: 57-69.

https://doi.org/10.1016/j.apgeog.2013.12.003

KEY FINDING: Focus on riparian restoration could provide more breeding habitat for the yellow-billed cuckoo, offset future habitat losses in adjacent watersheds, and increase regional connectivity for other threatened vertebrates that use riparian corridors.

Flesch, A.D. 2014. Spatiotemporal trends and drivers of population dynamics in a declining Sonoran Desert predator. Biological Conservation 175:110-118. https://doi.org/10.1016/j.biocon.2014.04.021

KEY FINDING: Abundance of ferruginous pygmy owls declined over 12 years in the Sonoran Desert of NW Mexico, but was persistently higher and varied less in areas with more nest cavities, riparian vegetation, and lower land-use intensity.

Hinojosa-Huerta, O., E. Soto-Montoya, M. Gomez-Sapiens, et al. 2013. The birds of the Cienega de Santa Clara, a wetland of international importance within the Colorado River Delta.

Ecological Engineering 59:61-73. https://doi.org/10.1016/j.ecoleng.2013.03.005

KEY FINDING: 261 species of birds have been detected in the Cienega de Santa Clara, the largest marsh in the Sonoran Desert, representing 71% of the species known to the Colorado River delta. Binational cooperation is essential to protect the Cienega in the long-term.

Merritt, D.M., and H.L. Bateman. 2012. Linking stream flow and groundwater to avian habitat in a desert riparian system. Ecological Applications 22:1973-1988. https://doi.org/10.1890/12-0303.1

KEY FINDING: Groundwater decline and decreased magnitude of fluvial disturbance along a perennial tributary of the Salt River caused significant shifts in riparian cover types from riparian forest to shrublands, decreasing bird species diversity and richness.

Brand, L.A., J.C. Stromberg, D.C. Goodrich, et al. 2011. Projecting avian response to linked changes in groundwater and riparian floodplain vegetation along a dryland river: A scenario analysis. Ecohydrology 4:130-142. https://doi.org/10.1002/eco.143

KEY FINDING: A modeling approach predicted that extreme groundwater declines along the upper San Pedro River would result in a precipitous decline in cottonwoods and willows and cause a severe decline in numbers of canopy-nesting, water-obligate, and spring migrant birds.

Brand, L.A., J.C. Stromberg, and B.R. Noon. 2010. Avian density and nest survival on the San Pedro River: Importance of vegetation type and hydrologic regime. Journal of Wildlife Management 74: 739-754. https://doi.org/10.2193/2008-217

KEY FINDING: Riparian management maintaining heterogeneous riparian vegetation produces the highest diversity and abundance of breeding birds on the San Pedro River, and cottonwood stands maintain the highest nest survival for some shrub-nesting birds.

Fish

Propst, D., J. Williams, K. Bestgen, et al., 2021. Standing between Life and Extinction: Ethics and Ecology of Conserving Aquatic Species in North American Deserts. University of Chicago Press.

KEY FINDING: Book. Conservation efforts to date on aquatic species native to North American deserts are summarized. Iconic species (razorback sucker, Gila trout, and Devils Hole pupfish) are addressed as are other fish and invertebrates inhabiting intermittent aquatic habitats.

Stewart, D.R., M.J. Butler, G. Harris, et al. 2017. Mark-recapture models identify imminent extinction of Yaqui catfish Ictalurus pricei in the United States. Biological Conservation 209:45-53. https://doi.org/10.1016/j.biocon.2017.02.010

KEY FINDING: 20 years of unsuccessful management of Yaqui catfish resulted in the collapse of the U.S. population, and habitat degradation and introgression from non-native fish threaten Mexican populations.

Budy, P., M.M. Conner, N.L. Salant, et al. 2015. An occupancy-based quantification of the highly imperiled status of desert fishes of the southwestern United States. Conservation Biology 29:1142-1152. https://doi.org/10.1111/cobi.12513

KEY FINDING: Review article. Dramatic declines in three species of desert fish were strongly associated with water development for human use.

Whitney, J. E., K.B. Gido, and D.L. Propst. 2014. Factors associated with the success of native and nonnative species in an unfragmented arid-land riverscape. Canadian Journal of Fisheries and Aquatic Sciences 71:1134-1145. https://doi.org/10.1139/cjfas-2014-0153

KEY FINDING: Native fish in the Gila River were more successful than nonnatives in a range of physicochemical conditions, basal resource supply rates, and nonnative communities.

Sheller, F.J., W.F. Fagan, and P.J. Unmack. 2006. Using survival analysis to study translocation success in the Gila topminnow (Poeciliopsis occidentalis). Ecological Applications 16:1771-1784.

KEY FINDING: Successful translocation of Gila topminnows should be done in late summer or fall, into ponds rather than streams, wells, or tanks, and not utilize individuals from Monkey Spring.

Fagan, W.F., P.J. Unmack, C. Burgess, et al. 2002. Rarity, fragmentation, and extinction risk in desert fishes. Ecology 83:3250-3256.

KEY FINDING: Desert fish species with the most fragmented historic distributions were nearly five times more likely to suffer local extirpations than species with continuous distributions

Insects

Howell, A.D., R. Alarcón, and R.L. Minckley. 2017. Effects of habitat fragmentation on the nesting dynamics of desert bees. Annals of the Entomological Society of America 110:233–243, https://doi.org/10.1093/aesa/saw081

KEY FINDING: Nesting dynamics of native solitary bees that inhabit fragments of Sonoran Desert were investigated. As landscape fragmentation increases, pollinator conservation must consider food sources, nesting requirements, and interactions with natural enemies.

Mammals

Erick J. Lundgren, E.J., D. Ramp, J.C. Stromberg, et al., 2021. Equids engineer desert water availability. Science 372: 491-495. DOI: 10.1126./science.abd6775

KEY FINDING: Feral horses and donkeys reintroduced to desert regions in the North American southwest dig wells that increased water availability, were used by a large number of species, and decreased distance between water sources for a variety of species.

Switalski, A.B., and H.L. Bateman. 2017. Anthropogenic water sources and the effects on Sonoran Desert small mammal communities. PeerJ 5: Article e4003. https://doi.org/10.7717/peerj.4003

KEY FINDING: All rodents were more abundant at anthropogenic water sites than control sites.

Horne, J.S., J.J. Hervert, S.P. Woodruff, et al. 2016. Evaluating the benefit of captive breeding and reintroductions to endangered Sonoran pronghorn. Biological Conservation 196:133-146. https://doi.org/10.1016/j.biocon.2016.02.005

KEY FINDING: Rates of change in a Sonoran pronghorn population were tied to amount of precipitation. Population viability was enhanced by maintenance of a captive population and establishment of two additional populations outside the current range.

Villarreal, M.L., R.H. Webb, L.M. Norman, et al. 2016. Modeling landscape-scale erosion potential related to vehicle disturbances along the USA-Mexico border. Land Degradation & Development 27:1106-1121. https://doi.org/10.1002/ldr.2317

KEY FINDING: Off-road vehicle use along the USA-Mexico border impacts desert ecosystems. Models revealed soil erosion potential hotspots adjacent to the border and within critical habitat for the threatened flat-tailed horned lizard and endangered Sonoran pronghorn.

Woodruff, S.P., P.M. Lukacs, D. Christianson, et al. 2016. Estimating Sonoran pronghorn abundance and survival with fecal DNA and capture-recapture methods. Conservation Biology 30:1102-1111. https://doi.org/10.1111/cobi.12710

KEY FINDING: Use of noninvasive techniques accurately monitored most of the Sonoran pronghorn population, provided the first survival estimates of this population in over two decades, and estimated the number of pronghorn using artificial water holes.

Buchalski, M.R., A.Y. Navarro, W.M. Boyce, et al. 2015. Genetic population structure of Peninsular bighorn sheep (Ovis canadensis nelsoni) indicates substantial gene flow across US–Mexico border. Biological Conservation 184. https://doi.org/10.1016/j.biocon.2015.01.006

KEY FINDING: Construction of a US–Mexico border fence or wind energy infrastructure would disrupt connectivity of this metapopulation of peninsular bighorn sheep.

Hoglander, C., B.G. Dickson, S.S. Rosenstock, et al. 2015. Landscape models of space use by desert bighorn sheep in the Sonoran Desert of southwestern Arizona. Journal of Wildlife Management 79:77-91. https://doi.org/10.1002/jwmg.818

KEY FINDING: Both quality of forage and water resources in areas of escape terrain should be considered in management strategies for desert bighorn sheep.

Klimova, A., A. Munguia-Vega, J.I. Hoffman, et al. 2014. Genetic diversity and demography of two endangered captive pronghorn subspecies from the Sonoran Desert. Journal of Mammalogy 95:1263-1277. https://doi.org/10.1644/13-MAMM-A-321

KEY FINDING: Extremely low levels of genetic diversity characterize both subspecies of Sonoran pronghorn (A. a. peninsularis and A. a. sonoriensis). Careful genetic management of both subspecies is needed in order to minimize the further loss of genetic variability.

Hagen, E.M., and J.L. Sabo. 2012. Influence of river drying and insect availability on bat activity along the San Pedro River, Arizona (USA). Journal of Arid Environments 84:1-8. https://doi.org/10.1016/j.jaridenv.2012.03.007

KEY FINDING: Intermittency of river flow indirectly affects bat activity along the San Pedro River via its effects on prey availability.

Bleich, V.C., J.P. Marshal, and N.G. Andrew. 2010. Habitat use by a desert ungulate: Predicting effects of water availability on mountain sheep. Journal of Arid Environments 74:638-645. https://doi.org/10.1016/j.jaridenv.2009.10.019

KEY FINDING: Developing additional sources of surface water increased availability of high-quality habitat for mountain sheep inhabiting Sonoran Desert mountains.

Morgart, J.R., J.J. Hervert, P.R. Krausman, et al. 2005. Sonoran pronghorn use of anthropogenic and natural water sources. Wildlife Society Bulletin 33:51-60.

KEY FINDING: Counter to previously published claims, Sonoran pronghorn were observed to drink freestanding water. Federal and state agencies should examine how to use water developments in the recovery of this endangered pronghorn subspecies.

Hervert, J.J., J.L. Bright, R.S. Henry, et al. 2005. Home-range and habitat-use patterns of Sonoran pronghorn in Arizona. Wildlife Society Bulletin 33:8-15.

KEY FINDING: Habitat preferences of Sonoran pronghorn were observed from 1994-2002. Pronghorn preferred palo verde-chain fruit cholla to creosote and palo verde-mixed cactl vegetation types.

deVos Jr., J.C., and W.H. Miller. 2005. Habitat use and survival of Sonoran pronghorn in years with above-average rainfall. Wildlife Society Bulletin 33: 35-42. https://doi.org/10.2193/0091-7648(2005)33[35:HUASOS]2.0.CO;2

KEY FINDING: 19 Sonoran pronghorn were monitored from 1983-1991. Creosote bush-white bursage-paloverde-mixed cacti associations were preferred, as were locations closer to water and further from roads. Mortality rates were low in years with above average rainfall.

Fox, L.M., P.R. Krausman, M.L. Morrison, et al. 2000. Water and nutrient content of forage in Sonoran pronghorn habitat, Arizona. California Fish and Game 86: 216-232. University of Arizona Master’s Thesis.

KEY FINDING: Sonoran pronghorn consumed plant species higher in moisture and selected nutrients than those not selected for forage. Predicted water intake from forages was not adequate to meet minimum water requirements.

Reptiles

Drost, C.A., J. E. Lovich, P.C. Rosen, et al., 2021. Non-native pond sliders cause long-term decline of native Sonora mud turtles: a 33-year before-after study in an undisturbed natural environment. Aquatic Invasions Volume 16 (in press).

KEY FINDING: The decline of native Sonora mud turtles after the introduction of non-native pond sliders at Montezuma Well, in Central Arizona, is documented. After the non-native turtles were trapped and rermoved, the Sonora mud turtle population rebounded.

Lara-Reséndiza, R.A., P.G. Tessaroa, B. Sinervo, et al., 2021. How will climate change impact fossorial lizard species? Two examples in the Baja California Peninsula. Journal of Thermal Biology, 95, Article 102811. https://doi.org/10.1016/j.jtherbio.2020.102811

KEY FINDING: Thermal quality of habitats in Baja California Peninsula were examined. Extinction risk was measured for two native fossorial lizard species, and both were found to be seriously affectedly climate change.

Kristin H. Berry, K.H., J.L Yee, and L.M. Lyren, 2020. Feral Burros and Other Influences on Desert Tortoise Presence in the Western Sonoran Desert. Herpetologica 76: 403–413. https://doi.org/10.1655/Herpetologica-D-20-00023.1

KEY FINDING: Impacts of multiple uses of land on Agassiz's desert tortoises in the western Sonoran Desert was assessed. The two top impacts were the presence of feral burros (negative) and the presence of Brittlebush plants (positive).

Bateman, H.L., and S.B. Riddle. 2020. Reptile community responses to native and non-native riparian forests and disturbance along two rivers in Arizona. River Research and Applications 36:492-502. https://doi.org/10.1002/rra.3587

KEY FINDING: Lizard abundance was greatest in cottonwood-willow forests, three of five lizard species were negatively associated with saltcedar-invaded habitat, and no species preferred saltcedar-dominated habitat.

Herrmann, H-W., K.M. Pozarowski, A. Ochoa, et al. 2017. An interstate highway affects gene flow in a top reptilian predator (Crotalus atrox) of the Sonoran Desert. Conservation Genetics 18:911-924. https://doi.org/10.1007/s10592-017-0936-8

KEY FINDING: Interstate I-10 has reduced gene flow in a population of the western diamond-backed rattlesnake in southern Arizona.

Abella, S.R., and K.H. Berry. 2016. Enhancing and restoring habitat for the desert tortoise. Journal of Fish and Wildlife Management 7:255-279. https://doi.org/10.3996/052015-JFWM-046

KEY FINDING: Reducing herbivory by nonnative animals, timing herbicide applications, and augmenting annual forage plants improve desert tortoise forage quality.

KEY FINDING: Off-road vehicle use impacts desert ecosystems. Models revealed soil erosion potential hotspots adjacent to the border and within critical habitat for the threatened flat-tailed horned lizard and endangered Sonoran pronghorn.

Sullivan, B.K., E.M. Nowak, and M.A. Kwiatkowski. 2015. Problems with mitigation translocation of herpetofauna. Conservation Biology 29:12-18. https://doi.org/10.1111/cobi.12336

KEY FINDING: Translocations of Gila monsters, Sonoran Desert tortoises, and western diamond-backed rattlesnakes were unsuccessful because translocated individuals often died or returned to the capture site.

Sullivan, B.K., K.O. Sullivan, D. Vardukyan, et al. 2014. Persistence of horned lizards (Phrynosoma spp.) in urban preserves of central Arizona. Urban Ecosystems 17:707-717. https://doi.org/10.1007/s11252-014-0353-4

KEY FINDING: Horned lizards were absent from one of ten large preserves where they were once present, perhaps as a result of a decline in seed-harvester ants.

Munguia-Vega, A., R. Rodriguez-Estrella, W.W. Shaw, et al. 2013. Localized extinction of an arboreal desert lizard caused by habitat fragmentation. Biological Conservation 157:11-20. https://doi.org/10.1016/j.biocon.2012.06.026

KEY FINDING: Extinction risk of a small ectotherm was studied in a fragmented desert landscape. Surveys corroborated the species went extinct after a few decades in all small, isolated habitat fragments, and cleared areas acted as complete barriers to dispersal.

Zylstra, E.R., R.J. Steidl, C.A. Jones, et al. 2013. Spatial and temporal variation in survival of a rare reptile: A 22-year study of Sonoran desert tortoises. Oecologia 173:107-116. https://doi.org/10.1007/s00442-012-2464-z

KEY FINDING: 22 years of data showed that survival of adult Sonoran desert tortoises decreased with drought severity, especially in arid areas nearest cities.

Riedle, J.D., P.C. Rosen, and R.T. Kazmaier, et al. 2012. Conservation status of an endemic kinosternid, Kinosternon sonoriense longifemorale, in Arizona. Chelonian Conservation and Biology 11:182-189. https://doi.org/10.2744/CCB-0982.1

KEY FINDING: A wide range of age classes should be maintained in an assurance colony of the Sonoyta mud turtle (Kinosternon sonoriense longifemorale).

Kwiatkowski , M.A., G. W. Schuett, and R. A. Repp. 2008. Does urbanization influence the spatial ecology of Gila monsters in the Sonoran Desert? Journal of Zoology 276:350-357. https://doi.org/10.1111/j.1469-7998.2008.00495.x

KEY FINDING: Spatial ecology of the Gila monster was observed to assess the effects of urbanization on this reptile. Gila monsters did not alter certain aspects of their spatial ecology in response to low levels of human activity.

Rosen, P.C., and C. H. Lowe, 1994. Highway mortality of snakes in the Sonoran Desert of southern Arizona. Biological Conservation 68:143-148. https://doi.org/10.1016/0006-3207(94)90345-X

KEY FINDING: Two taxa of special conservation interest, the Mexican rosy boa and the Organ Pipe shovel-nosed snake, appear to be strongly impacted by highway mortality. Paved roadways are a substantial threat to snake populations.

Sonoran Desert Invasive Species

Rhodes, A.C., J. Rutledge, B. DuPont, et al., 2021. Targeted Grazing of an Invasive Grass Improves Outcomes for Native Plant Communities and Wildlife Habitat. Rangeland Ecology & Management 75: 41-50. https://doi.org/10.1016/j.rama.2020.11.007

KEY FINDING: Targeted vs.light cattle grazing in native-dominated and buffelgrass-dominated plant communities was tracked in South Texas. Targeted grazing improved species richness and cover of native plants and could be a useful strategy to reduce the impact of buffelgrass.

De Albuquerque, F.S., M. Angel Macias-Rodriguez, A. Burquez, et al. 2019. Climate change and the potential expansion of buffelgrass (Cenchrus ciliaris L., Poaceae) in biotic communities of Southwest United States and northern Mexico. Biological Invasions 21:3335-3347. https://doi.org/10.1007/s10530-019-02050-5

KEY FINDING: Habitat suitability for African buffelgrass is high in some areas in southern Arizona and northern Mexico. Climate change models showed fewer opportunities for buffelgrass to expand than to contract across its range.

Drake, J.C., K.L. Griffis-Kyle, and N.E. McIntyre. 2017. Graph theory as an invasive species management tool: Case study in the Sonoran Desert. Landscape Ecology 32:1739-1752. https://doi.org/10.1007/s10980-017-0539-2

KEY FINDING: The invasive American bullfrog may use artificial water catchments to disperse into previously inaccessible areas. Waters were identified that could lead to the spread of this invasive species.

Sonoran Desert Plants

Conver, J.L., E. Yarwood, L.D. Hetherington, et al. 2020. Nurse rock microclimates significantly buffer exposure to freezing temperature and moderate summer temperature. Journal of Arid Environments 177: Article 104140. https://doi.org/10.1016/j.jaridenv.2020.104140

KEY FINDING: Results suggest that the protection from freezing temperature by rocks in winter is more beneficial to the saguaro than extreme temperature amelioration during summer in the cold-limited frontiers of the species' range.

Felix-Burruel, R.E, E. Larios, E. Bustamante, et al. 2019. Nonlinear modeling of saguaro growth rates reveals the importance of temperature for size-dependent growth. American Journal of Botany 106:1300-1307. https://doi.org/10.1002/ajb2.1358

KEY FINDING: Higher temperature variance at the beginning of summer was most detrimental to saguaro growth in 13 populations studied in the Sonoran Desert. Rising temperatures with climate change are likely to affect population dynamics of the saguaro.

Rodríguez-Buriticá, S., D.E. Winkler, R.H. Webb, et al. 2019. Local temporal trajectories explain population-level responses to climate change in saguaro (Carnegiea gigantea). Ecosphere 10: Article e02844. https://doi.org/10.1002/ecs2.2844

KEY FINDING: A 48-year data set of marked saguaros suggested that topographic differences interacted with climatic fluctuations to produce unexpected demographic patterns including large recruitment events during periods of relatively unfavorable climate conditions.

Winkler, D.E., J.L. Conver, T.E. Huxman, et al. 2018. The interaction of drought and habitat explain space-time patterns of establishment in saguaro (Carnegiea gigantea). Ecology 99:621-631. https://doi.org/10.1002/ecy.2124

KEY FINDING: Saguaros were studied in two parts of Saguaro National Park in southern Arizona, and the most suitable habitat type for saguaro establishment shifts to higher elevations during droughts.

Albuquerque, F., B. Benito, M.A. Macias Rodriguez, et al. 2018. Potential changes in the distribution of Carnegiea gigantea under future scenarios. Peerj 6: Article e5623. https://doi.org/10.7717/peerj.5623

KEY FINDING: Annual precipitation and maximum temperature of the warmest month have the greatest influence on saguaro distribution. Predicted changes in climate may result in a substantial contraction of suitable habitat for saguaros.

Conver, J.L., T. Foley, D.E. Winkler, et al. 2017. Demographic changes over > 70 yr in a population of saguaro cacti (Carnegiea gigantea) in the northern Sonoran Desert. Journal of Arid Environments 139:41-48. https://doi.org/10.1016/j.jaridenv.2016.12.008

KEY FINDING: Total number of detected saguaros in Saguaro National Park decreased by over 31% from 1941-2012. Demographic changes may stem from long-term drought, higher temperatures, and land-use changes (loss of nurse trees due to wood-cutting).

Orum, T.V., N. Ferguson, and J.D. Mihail. 2016. Saguaro (Carnegiea gigantea) mortality and population regeneration in the cactus forest of Saguaro National Park: Seventy-five years and counting. PLOS One 11: Article e0160899. https://doi.org/10.1371/journal.pone.0160899

KEY FINDING: The height structure of saguaros in the Rincon Mt. District of Saguaro National Park has shifted from predominantly large to mostly small saguaros in the last 20 years. Saguaros under 40 years old and well-protected by vegetation are most likely to survive.

Abella, S.R., K.L. O’Brien, and M.W. Weesner. 2015. Revegetating disturbance in national parks: Reestablishing native plants in Saguaro National Park, Sonoran Desert. Natural Areas Journal 35:18-25. https://doi.org/10.3375/043.035.0104

KEY FINDING: In Saguaro National Park, Arizona, the results of revegetating after a 2006 reconstruction project showed that survival one year after planting was high for 1,587 individuals of 33 native perennial species, and that survival was generally consistent across species.

Goettsch, B., C. Hilton-Taylor, G. Cruz-Piñón, et al. 2015. High proportion of cactus species threatened with extinction. Nature Plants 1: Article 15142. https://doi.org/10.1038/nplants.2015.142

KEY FINDING: The global species assessment for the Cactaceae under the IUCN Red List Categories and Criteria show that 31% of the 1,478 evaluated cactus species were threatened, confirming the anthropogenic pressures on biodiversity in arid lands.

Clark, K.B. 2011. Fragmentation effects on vegetation and resulting vertebrate species distributions in the Sonoran Desert. Journal of the Arizona-Nevada Academy of Science 42:84-91. https://doi.org/10.2181/036.042.0204

KEY FINDING: Vertebrate species present on habitat fragments of various sizes were studied in the Sonoran Desert. Increased grass cover and decreased shrub cover on fragments closely corresponded with decreased abundance of several species.

Zuniga-Tovar, B., and H. Suzan-Azpiri. 2010. Comparative population analysis of desert ironwood (Olneya tesota) in the Sonoran Desert. Journal of Arid Environments 74:173-178. https://doi.org/10.1016/j.jaridenv.2009.08.004

KEY FINDING: Extraction of trees and branches constitutes a severe risk for ironwood tree populations, a keystone species in Sonoran Desert ecosystems.

Sonoran Desert Soils

Lopez-Lozano, N.E., M.G. Carcano-Montiel, and Y. Bashan. 2016. Using native trees and cacti to improve soil potential nitrogen fixation during long-term restoration of arid lands. Plant and Soil 403:317-329. https://doi.org/10.1007/s11104-016-2807-3

KEY FINDING: Nitrogen, next to water, is the most limiting factor for productivity in arid terrestrial ecosystems. Successful long-term restoration improved the potential N2 fixation to a level similar to undisturbed lands.

KEY FINDING: Off-road vehicle use prompted concerns about human impacts on desert ecosystems. Models revealed soil erosion potential hotspots adjacent to the border and within critical habitat for the threatened flat-tailed horned lizard and endangered Sonoran pronghorn.

Belnap, J. 2003. The world at your feet: Desert biological soil crusts. Frontiers in Ecology and the Environment:181–189.

KEY FINDING: Biological crusts contain organisms that are vital in creating and maintaining fertility in otherwise infertile desert soils. These organisms are extremely vulnerable to climate change and disturbances such as off‐road vehicles and grazing livestock.

Sonoran Desert Waters

Anthropogenic Water Sources

Switalski, A.B., and H.L. Bateman. 2017. Anthropogenic water sources and the effects on Sonoran Desert small mammal communities. PeerJ 5: Article e4003. https://doi.org/10.7717/peerj.4003

KEY FINDING: All rodents were more abundant at anthropogenic water sites than control sites.

Griffis-Kyle, K.L., J.J. Kovatch, and C. Bradatan. 2014. Water quality: A hidden danger in anthropogenic desert catchments. Wildlife Society Bulletin 38:148-151. https://doi.org/10.1002/wsb.358

KEY FINDING: Amphibians and dragonflies in the Sonoran Desert had lower species richness in artificial water catchments (AWC) than in natural rock pools, due to higher levels of ammonia in AWC. Amphibian species richness was negatively associated with ammonia concentration.

Ephemeral (Intermittently Flowing) Waters

Allen, D.C., T. Datry, K.S. Boersma, et al. 2020. River ecosystem conceptual models and non-perennial rivers: A critical review. Wires Water 7: Article e1473. https://doi.org/10.1002/wat2.1473

KEY FINDING: Conceptual models of river science should be modified to accommodate the drying that occurs in ephemeral rivers.

Rogosch, J.S., and J.D. Olden. 2019. Dynamic contributions of intermittent and perennial streams to fish beta diversity in dryland rivers. Journal of Biogeography 46:2311-2322. https://doi.org/10.1111/jbi.13673

KEY FINDING: In intermittent sites, native fish contributed more to beta-diversity than non-native fish. Despite weakening policy protections of intermittent streams, these habitats are critical for supporting local species persistence and regional biodiversity.

Goodrich, D.C., W.G. Kepner, L.R. Levick, et al. 2018. Southwestern intermittent and ephemeral stream connectivity. Journal of the American Water Resources Association 54:400-422. https://doi.org/10.1111/1752-1688.12636

KEY FINDING: Review Article. Factors affecting the hydrologic, chemical, and ecological connectivity of ephemeral and intermittent streams on perennial or intermittent rivers in the arid southwestern U.S. are reviewed, with a detailed example of the San Pedro Basin.

Levick, L., S. Hammer, R. Lyon, et al. 2018. An ecohydrological steam type classification of intermittent and ephemeral streams in the southwestern United States. Journal of Arid Environments 155:16-35. https://doi.org/10.1016/j.jaridenv.2018.01.006

KEY FINDING: An ecohydrological stream type classification was developed to improve decision making for ephemeral and intermittent streams at four southwestern U.S. military reservations: Fort Irwin, Yuma Proving Ground, Fort Huachuca, and Fort Bliss.

Creed, I.F., C.R. Lane, J.N. Serran, et al. 2017. Enhancing protection for vulnerable waters. Nature Geoscience 10:809-815. https://doi.org/10.1038/ngeo3041

KEY FINDING: A scientific rationale and three policy options for all levels of government is presented that would protect vulnerable fresh water systems.

Acuna, V., M. Hunter, and A. Ruhi. 2017. Managing temporary streams and rivers as unique rather than second-class ecosystems. Biological Conservation 211:12-19. https://doi.org/10.1016/j.biocon.2016.12.025

KEY FINDING: Temporary streams and rivers that support biodiversity in arid landscapes are rapidly degrading. Temporary streams and rivers must be defined as unique ecosystems and conservation targets in which biological and hydrological data is systematically collected.

Stromberg, J.C., D.L. Setaro, and E.L. Gallo, et al. 2017. Riparian vegetation of ephemeral streams. Journal of Arid Environments 138:27-37. https://doi.org/10.1016/j.jaridenv.2016.12.004

KEY FINDING: Plant communities at seven ephemeral streams distributed among three climatic settings in Arizona were assessed. Increasing aridity will reduce the number of plant species in riparian zones, drive declines in herbaceous cover, and convert riparian savanna to scrubland.

Leigh, C., A.J. Boulton, J.L. Courtwright, et al. 2015. Ecological research and management of intermittent rivers: An historical review and future directions. Freshwater Biology 61 (Special Issue):1181-1199. https://doi.org/10.1111/fwb.12646

KEY FINDING: Review Article. Research on intermittent rivers from its early focus on natural history through its current application in management and policy is reviewed.

Katz, G.L., M.W. Denslow, and J.C. Stromberg. 2012. The Goldilocks effect: Intermittent streams sustain more plant species than those with perennial or ephemeral flow. Freshwater Biology 57:467-480. https://doi.org/10.1111/j.1365-2427.2011.02714.x

KEY FINDING: Ephemeral, intermittent, and perennial flow reaches were monitored for three desert rivers in AZ: Lower Cienega Creek, Hassayampa River, and Lower San Pedro River. Conservation of desert riparian diversity requires protection of all three types of flow sites.

Hultine, K.R., and S.E. Bush. 2011. Ecohydrological consequences of non-native riparian vegetation in the southwestern United States: A review from an ecophysiological perspective.

Water Resources Research 47: Article W07542. https://doi.org/10.1029/2010WR010317

KEY FINDING: Review Article. Climate change, intensive land use, and the progressive expansion of nonnative plant species in riparian zones pose significant threats to water resources in arid regions where evapotranspiration may exceed annual rainfall.

Larned, S.T., T. Datry, and D.B. Arscott, et al. 2010. Emerging concepts in temporary-river ecology. Freshwater Biology 55:717-738. https://doi.org/10.1111/j.1365-2427.2009.02322.x

KEY FINDING: Review article. Temporary rivers and streams are hydrologically dynamic freshwater ecosystems and may be increasing in regions affected by climatic drying. Models address the unique properties and primary objectives for management of temporary rivers.

Levick, L.R., J. Fonseca, D.C. Goodrich, et al. 2008. The ecological and hydrological significance of ephemeral and intermittent streams in the arid and semi-arid American Southwest. U.S. Environmental Protection Agency and USDA/ARS Southwest Watershed Research Center, EPA/600/R-08/134, ARS/233046. 116 pp. https://www.epa.gov/sites/production/files/2015-03/documents/ephemeral_streams_report_final_508-kepner.pdf

KEY FINDING: Review article. The current scientific understanding of the ecology and hydrology of ephemeral and intermittent streams is comprehensively reviewed. Cumulative impacts from anthropogenic uses of individual streams must be critically evaluated.

Bagstad, K.J., J.C. Stromberg, and S.J. Lite. 2005. Response of herbaceous riparian plants to rain and flooding on the San Pedro River, Arizona, USA. Wetlands 25:210-223.

KEY FINDING: Both disturbance and increased moisture conditions caused by floods, as well as moisture from seasonal rains, contribute to increased richness and cover of herbaceous plants within the flood plain of the San Pedro River.

Goodrich, D.C., D. G. Williams, C.L. Unkrich, et al. 2004. Comparison of methods to estimate ephemeral channel recharge, Walnut Gulch, San Pedro River Basin, Arizona. Pp. 77-99. In: Recharge and Vadose Zone Processes: Alluvial Basins of the Southwestern United States. F.M. Phillips, J.F. Hogan and B. Scanion, editors. Water Science and Application 9, American Geophysical Union: Washington, D.C. https://www.tucson.ars.ag.gov/unit/publications/PDFfiles/1579.pdf

KEY FINDING: Ephemeral channel transmission loss represents an important groundwater-surface water exchange in arid and semiarid regions and is potentially a significant source of recharge at the basin scale.

Rivers and Riparian Ecosystems

Shamir, E., E.M. Tapia-Villaseñor, M.B. Cruz-Ayala, et al., 2021. A Review of Climate Change Impacts on the USA-Mexico Transboundary Santa Cruz River Basin. Water 13: Article 1390. https://doi.org/10.3390/w13101390

KEY FINDING: Relevant studies of four weather systems that affect the region’s precipitation with climate projections for the 21st century are reviewed. Drying trends are projected for the 21st century, requiring plans and actions to attain sustainable water resources management.

La Porte, A.M., R.W. Mannan, and S. Brewer. 2020. Riparian conservation facilitated expansion of gray hawks. Journal of Wildlife Management 84:911-920. https://doi.org/10.1002/jwmg.21851

KEY FINDING: 25 years after the San Pedro Riparian Conservation area was established and grazing and agriculture were eliminated, the gray hawk population increased and expanded into areas now more dominated by grassland.

Bateman, H.L., and D.M. Merritt. 2020. Complex riparian habitats predict reptile and amphibian diversity. Global Ecology and Conservation 22: Article e00957. https://doi.org/10.1016/j.gecco.2020.e00957

KEY FINDING: Native riparian trees and stands mixed with native and non-native trees supported greater diversity and abundance of lizard fauna compared to monotypic stands of non-native trees.

KEY FINDING: Significantly more lizards were found in the two types of native forests (cottonwood-willow and mesquite), characterized by high woody species richness, than in the non-native saltcedar stands, and no species preferred saltcedar‐dominated habitat.

Allen, D.C., D.A. Kopp, K.H. Costigan, et al. 2019. Citizen scientists documented long-term streamflow declines in intermittent rivers of the desert southwest, USA. Freshwater Science 38:244-256. https://doi.org/10.1086/701483

KEY FINDING: Perennial water decreased from 2006-2016 in the Agua Fria River and Cienega Creek. A decline in habitat connectivity for large fish in the Agua Fria River suggests that habitat connectivity of fish populations may decline as climate becomes more arid.

Alexander, L.C., B. Autrey, J. DeMeester, et al. 2015. Connectivity of streams & wetlands to downstream waters: A review & synthesis of the scientific evidence. United States Environmental Protection Agency: EPA/600/R-14/475F. 408 pp. https://www.tucson.ars.ag.gov/unit/publications/PDFfiles/2302.pdf

KEY FINDING: Review Article. More than 1,200 peer-reviewed publications are reviewed. Current scientific understanding about water connectivity and the mechanisms by which streams and wetlands affect the integrity of downstream waters is summarized.

Nguyen, U., E.P. Glenn, P.L. Nagler, et al. 2015. Long-term decrease in satellite vegetation indices in response to environmental variables in an iconic desert riparian ecosystem: The Upper San Pedro, Arizona, United States. Ecohydrology 8:610-625. https://doi.org/10.1002/eco.1529

KEY FINDING: Satellite vegetation indices of the southern (perennially flowing) and northern (ephemerally flowing) upper San Pedro River showed that riparian forest declined by 20% only in the northern reach. Changes were probably due to climate change, regional groundwater pumping, changes in monsoon rain events, and lack of overbank flooding.

Richter, H.E., B. Gungle, L.J. Laurel, et al. 2014. Development of a shared vision for groundwater management to protect and sustain baseflows of the upper San Pedro River, Arizona, USA. Water 6:2519-2538. https://doi.org/10.3390/w6082519

KEY FINDING: Groundwater pumping along portions of the San Pedro River has depleted aquifer storage that supports baseflow. 23 agencies, business interests, and NGO’s jointly acquired 2,250 hectares of land along the river to protect it.

Garssen, A.G., J.T.A. Verhoeven, and M.B. Soons. 2014. Effects of climate-induced increases in summer drought on riparian plant species: A meta-analysis. Freshwater Biology 59:1052-1063. https://doi.org/10.1111/fwb.12328

KEY FINDING: A meta-analysis showed that the projected increase in the duration and intensity of drought periods, especially droughts longer than 30 days, may narrow the riparian wetland zone with typical hydric species and accelerate losses of riparian wetland species.

Stromberg, J.C., K.E. McCluney, and M.D. Dixon, et al. 2013. Dryland riparian ecosystems in the American Southwest: Sensitivity and resilience to climatic extremes. Ecosystems 16:411–415. https://doi.org/10.1007/s10021-012-9606-3

KEY FINDING: Review Article. Riparian zones are crucial for maintaining regional diversity. Maintaining connectivity between stream segments, channels and floodplains, and groundwater and surface water are essential for riparian ecosystems to adapt to future climate change.

Stromberg, J.C., V.B. Beauchamp, M.D. Dixon, et al. 2007. Importance of low-flow and high-flow characteristics to restoration of riparian vegetation along rivers in arid southwestern United States. Freshwater Biology 52:651–679. https://doi.org/10.1111/j.1365-2427.2006.01713.x

KEY FINDING: In Arizona's Sonoran Desert, the combination of perennial stream flows, shallow groundwater in the riparian aquifer, and frequent flooding results in high plant species diversity, landscape heterogeneity, and abundant pioneer wetland plant species in the floodplain.

Stromberg, J.C., R. Tiller, and B. Richter. 1996. Effects of groundwater decline on riparian vegetation of semiarid regions: The San Pedro, Arizona. Ecological Applications 6:113-131. https://doi.org/10.2307/2269558

KEY FINDING: The aquifer that sustains Arizona's San Pedro River riparian ecosystem is threatened by regional groundwater declines and localized pumping from the alluvial aquifer. The role of shallow groundwater in the San Pedro River plant community is addressed.

Boulton, A.J., H.M. Valett, and S.G. Fisher. 1992. Spatial distribution and taxonomic composition of the hyporheos of several Sonoran Desert streams. Archiv fur Hydrobiologie 125:37-61. https://www.sciencebase.gov/catalog/item/5057a15ce4b01ad7e0286ea2

KEY FINDING: A survey of desert streams in Arizona revealed a biodiversity-rich hyporheos zone which can be viewed as a functional subunit of desert stream ecosystems. The existence of a rich hyporheic biota indicates the importance of subsurface processes in desert streams.

Springs

Keara, S., A.D. Walters, T.J. Haan, et al. 2018. Variation among macroinvertebrate communities suggests the importance of conserving desert springs. Aquatic Conservation 28:944-953. https://doi.org/10.1002/aqc.2894

KEY FINDING: Five springs in the northern Chihuahuan Desert of western Texas and southeastern New Mexico containing unique communities and endemic species should be conserved for their biodiversity.

Bogan, M.T., N. Noriega-Felix, S.L. Vidal-Aguilar, et al. 2014. Biogeography and conservation of aquatic fauna in spring-fed tropical canyons of the southern Sonoran Desert, Mexico.

Biodiversity and Conservation 23:2705-2748. https://doi.org/10.1007/s10531-014-0745-z

KEY FINDING: Spring-fed habitats are hotspots of freshwater biodiversity and frequently the only year-round source of surface water in arid regions like the Sonoran Desert. Biodiversity was documented at 19 sites in the southern Sonoran Desert.

Wetlands

Minckley, T. A., D.S. Turner, and S.R. Weinstein. 2013. The relevance of wetland conservation in arid regions: A re-examination of vanishing communities in the American Southwest.

Journal of Arid Environments 88:213-221. https://doi.org/10.1016/j.jaridenv.2012.09.001

KEY FINDING: Review Article. Desert wetlands in the American southwest are in the lowest categories of land stewardship. Conservation of desert wetlands would benefit global biodiversity.

Transboundary Issues

Erg, B., C. Groves, M. McKinney, et al. 2015. Transboundary conservation: a systematic and integrated approach. International Union for the Conservation of Nature: Gland, Switzerland.

KEY FINDING: A case for transboundary conservation is made and innovative methods based on contemporary principles is presented. Such methods will help transboundary conservation managers address challenges specific to transboundary conservation.

Milman, A., and C.A. Scott. 2010. Beneath the surface: intranational institutions and management of the United States-Mexico transboundary Santa Cruz aquifer. Environment and Planning C Government and Policy 28:528-551. https://doi.org/10.2305/IUCN.CH.2015.PAG.23.en

KEY FINDING: The Santa Cruz aquifer, shared by the U.S. and Mexico, was used to identify the factors leading to effective management of transboundary groundwaters.

Wildfire

Aslan, C. E., S. Souther, S. Stortz, et al., 2021. Land management objectives and activities in the face of projected fire regime change in the Sonoran desert. Journal of Environmental Management 280, Article 111644. https://doi.org/10.1016/j.jenvman.2020.111644

KEY FINDING: Fire regime change has varying degrees of impact on human communities and institutions. Poorly funded tribal jurisdictions were less likely to achieve objectives related to conservation of natural and cultural resources, while well-funded military installations were more likely to receive the protections they required.

Roldan-Nicolau, E., T. Terrazas, M. Navarrete Montesinos, et al. 2020. Effect of buffelgrass fires on two Sonoran Desert trees: Bark and structural analyses. Journal of Arid Environments 178: Article 104199. https://doi.org/10.1016/j.jaridenv.2020.104166

KEY FINDING: Drought-resistant traits of Bursera microphylla improve fire survival by providing more resistance to heat inputs from buffelgrass. Traits of Olneya tesota increase fire intensity.

Moloney, K.A., E.L. Mudrak, A. Furentes-Ramirez, et al. 2019. Increased fire risk in Mojave and Sonoran shrublands due to exotic species and extreme rainfall events. Ecosphere 10: Article e02592. https://doi.org/10.1002/ecs2.2592

KEY FINDING: Increased rainfall in southwestern U.S. deserts increases biomass of annual plants, especially in the inter-shrub areas, which can lead to enhanced fire risk. Dominance of exotic annuals at could further enhance this risk.

Gasc, A., B.L. Gottesman, D. Francomano, et al. 2018. Soundscapes reveal disturbance impacts: Biophonic response to wildfire in the Sonoran Desert Sky Islands. Landscape Ecology 33:1399-1415. https://doi.org/10.1007/s10980-018-0675-3

KEY FINDING: 55% of recordings from non-burned sites contained insect sounds compared to 18% from burned sites; this is a new method to measure disturbance at burned sites.

Fuentes-Ramirez, A., J.W. Veldman, C. Holzapfel, et al. 2016. Spreaders, igniters, and burning shrubs: Plant flammability explains novel fire dynamics in grass-invaded deserts. Ecological Applications 26:2311-2322. https://doi.org/10.1002/eap.1371

KEY FINDING: Grasses quickly spread fire to native plants, which burn longer and ignite dead creosote branches, which ignite living branches, resulting in intense fires without historical precedent in the Sonoran Desert.

Wildlife Corridors

Gregory, A, E. Spence, P. Beier , et al., 2021. Toward Best Management Practices for Ecological Corridors. Land 10: 140. https://doi.org/10.3390/land10020140

KEY FINDING: Review article. This document has been assembled to provide managers with a convenient guidance document and tool to assist in them in applying scientific management principles to management of wildlife corridors.

González-Saucedo, Z.Y., A. González-Bernal, and E. Martínez-Meyer, 2021. Identifying priority areas for landscape connectivity for three large carnivores in northwestern Mexico and southwestern United States. Landscape Ecology 36: 877–896. https://doi.org/10.1007/s10980-020-01185-4

KEY FINDING: Large, high-quality areas of habitat in Mexico and the U.S. were found that could serve as wildlife corridors for black bears, pumas, and Mexican wolves. Binational plans must insure landscape connectivity for large carnivores moving between Mexico and the U.S.

Drake, J.C., K.Griffis-Kyle, and N.E. McIntyre. 2017. Using nested connectivity models to resolve management conflicts of isolated water networks in the Sonoran Desert. Ecosphere 8: Article e01647. https://doi.org/10.1002/ecs2.1652

KEY FINDING: A method is proposed to create exclusion areas and site new waters to help mitigate increasing spread of invasive species like the bullfrog, while maintaining resource availability and local connectivity for economically important species like the mule deer.

Flesch, A.D., C.W. Epps, J.W. Cain, et al. 2010. Potential effects of the United States-Mexico border fence on wildlife. Conservation Biology 24:171-181. https://doi.org/10.1111/j.1523-1739.2009.01277.x

Bennett, A.F. 1999, 2003. Linkages in the Landscape: The Role of Corridors and Connectivity in Wildlife Conservation. IUCN: Gland, Switzerland, and Cambridge, UK. Pp. 254.https://portals.iucn.org/library/efiles/documents/FR-021.pdf

KEY FINDING: This book comprehensively addresses the role of corridors and connectivity in wildlife conservation.