The global climate is changing. Shifts to warmer daytime and night temperatures, and altered precipitation patterns such as timing and intensity of precipitation, are stressing natural systems and creating optimal conditions for wildfires, pests, diseases, and invasive species (AFWA 2009). Arizona has already begun to experience these climate shifts and the new or intensified corresponding threats that result from such changes.
Changes in Temperature Regimes
According to a 2014 report by the U.S. Global Change Research Program, annual average temperatures in the Southwest are projected to rise by 2.5°F to 5.5°F by 2041-2070 and by 5.5°F to 9.5°F by 2070-2099 under current emission rates (Garfin et al. 2014). In Arizona, the increase in average temperatures is predicted to be coupled with reduced precipitation, especially in the winter and spring months (Mellillo et al. 2014).
Changes in Precipitation and Hydrological Regimes
In the Southwest, water is our greatest limiting resource. As the climate changes and water availability decreases, all living things will feel the impact of an increasingly limited supply of this vital natural resource. Climate models suggest that Arizona may continue to see a reduction in annual precipitation (Brown et al. 1997, Burrell et al. 2020). In addition to less moisture overall, reduced snowpack across the entire Colorado River Basin would result in reduced spring runoff into rivers and reservoirs, and less surface water available to sustain growing human populations. Less water for us means less water for wildlife. A long-term trend of dry winters and reduced monsoonal precipitation, combined with increasing water consumption by a growing human population, may cause once-perennial streams to run dry, resulting in complete loss of valuable aquatic and riparian habitat. We may also see significant modifications to the hydrological regime of many aquatic systems, especially those with interrupted perennial, intermittent, or ephemeral flow patterns.
For example, a 2014 modeling effort to predict changes to hydrologic connectivity in the Verde River Basin suggested that, “flowing portions of the river network will diminish between 8% and 20% in spring and early summer and become increasingly isolated by more frequent and longer stretches of dry channel fragments” (Jaeger et al. 2014). The increased extent and duration of dry channel segments has negative implications for the entire ecosystem by disrupting natural energy and nutrient transport patterns, as well as anticipated changes to associated vegetation communities. Impacts to native fishes are particularly concerning as their access to spawning and rearing habitat and seasonal refuge areas would be increasingly limited (Jaeger et al. 2014).
Another study of impacts of several climate change scenarios on the Upper San Pedro River riparian area in southeastern Arizona indicated an on-going transition from riparian to more xeric habitat types, especially when the cumulative effects of groundwater pumping for agriculture and urban water use were considered (Kepner et al. 2016). A reduction in the cottonwood-willow gallery forest community would have dramatic impacts on many migratory bird species who rely on these lush habitats. Springs and ciénegas, which exist where groundwater intercepts the surface, are at high risk of complete conversion resulting in habitat loss for several of Arizona’s at-risk species including the desert pupfish, Gila topminnow, Chiricahua leopard frog, and several springsnail species.
Case Study: Collaborating for Water Conservation
In partnership with Arizona Land and Water Trust (ALWT), AZGFD recently completed a five-year water conservation project on the Lower San Pedro River Wildlife Area. This 2,000-acre property features miles of perennial surface water and mature cottonwood galleries, creating quality habitats for several SGCN, including southwestern willow flycatcher, yellow-billed cuckoo, and lowland leopard frog. However, the wildlife area, along with much of the surrounding landscapes, has been degraded in recent decades due, in part, to groundwater pumping and invasive plants, such as salt cedar.
To help reverse these trends, AZGFD collaborated with ALWT to reduce groundwater pumping at the site. By converting 100 acres of high-water-use crop to a low-water-use native grass pasture, more than 700 million gallons of water (approximately 2,000 acre-feet) have remained in the river system over the five-year project term for the benefit of wildlife, riparian vegetation, and rural water users. Thanks to AZGFD’s diligent management of the fields with local agricultural cooperators, the native grass pasture has become home to a flock of turkeys with enhanced habitat for passerine, migratory birds, rodents, and herpetofauna. The water savings developed through this project represent a major conservation win for AZGFD and ALWT, as this project represents the largest water transaction on the Lower San Pedro River for ALWT's Desert Rivers Program.
Habitat Shifts and Ecosystem Conversion
A changing climate has the potential to greatly alter the delicate relationships between the biotic and abiotic elements in any ecosystem. The result can be ecosystem conversion, where vegetative communities are slowly replaced by species better suited to a warmer, drier climate (Garfin et al. 2014). Ultimately, these conversions can result in habitat shifts, leading to replacement of entire wildlife communities.
Although drought is a top concern, changes in the timing of precipitation events can also have adverse effects by altering competitive interactions between plant species, thus changing community composition. For example, increases in winter precipitation may favor tree establishment and growth at the expense of grasses (Bolin et al. 1986). Increased winter precipitation has also been shown to favor shrub expansion in areas of southeastern Arizona (Brown et al. 1997). These same authors documented major changes in population dynamics and community composition of animals on the study site, from local extinctions (including one keystone species) to decreases in formerly abundant species, while other species increased in numbers.
As temperatures increase and precipitation patterns change, Arizona may experience terrestrial ecosystem conversion from forest to grassland and from grassland to desert, forcing wildlife to adapt or migrate to more suitable areas (if suitable habitat exists). Those that do not have dispersal capabilities, or where barriers restrict movement, loss of biodiversity and/or species extinction could result. The “sky islands” of southeastern Arizona are particularly vulnerable to conversion, and in some areas the hotter, drier conditions and intense wildfires are already causing portions of these biodiversity hotspots to transition from mixed-conifer and ponderosa pine forest to shrub and annual grass-dominated communities. In addition, changes in climate are predicted to cause a shift in timing of important physiological events in the life cycles of plants and animals, such as plants and host-specific pollinators. This may lead to misalignment of food availability and reproduction, disrupting the balance of natural systems and putting additional stress on vulnerable species (AFWA 2009; Margolis et al. 2011).
Drought and other changes to precipitation regimes can lead to habitat shifts and influence populations of large ungulates such as elk and white-tailed deer. Changes to precipitation directly affect plant communities as well as quality and quantity of forage for ungulates (Walther et al. 2002). Forage quality and quantity can influence ungulate survival, body condition of individuals, and calving success, among many other factors (Rubin et al. 2000; Bender et al. 2013). Although many of Arizona’s ungulates are not considered SGCN, these large, wide-ranging species have considerable influence on the habitats wherever they occur, and play an important role in the natural ecosystems that support many SGCN, such as overgrazing by elk which may reduce regeneration of aspen trees in sensitive alpine habitats (Scotter 1980; Clement et al 2019).
Drier conditions are also expected to have economic impacts, especially in the agriculture sector where long-term drought can reduce important crops like fruits and nuts, and have devastating effects on livestock production due to lack of forage and water. Tourism and outdoor recreation industries would also be impacted due to reduced streamflow and a shorter snow season (Garfin et al. 2014). Many of the outdoor recreational activities that Arizona supports could be greatly restricted due to lack of water. For the 1.5 million residents and countless visitors who routinely participate in water-dependent activities like fishing, kayaking, snowboarding, and birding, a warming climate will almost certainly adversely affect these pursuits and have significant residual impacts to local and statewide economies.
There is no doubt that the combination of a hotter and drier climate will affect every aspect of our lives and the lives of the plants and animals with which we share the extraordinary Arizona landscape. However, there are steps that we can take to reduce impacts and promote resilience as conditions change.
Adaptation Planning Approach and the AWCS
In 2014, the Intergovernmental Panel on Climate Change’s 5th Assessment Report clearly stated the imminent threat before us as “Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia” (IPCC 2014). However, what is less certain is how conditions will change, the rate at which they will do so, and how natural communities and individual species will respond and cope to changes in the environment. In light of this uncertainty and due to the complex interactions between existing threats and climate change, we chose to conduct a broad assessment of major threats to native fish and wildlife species rather than a vulnerability assessment specific to climate change impacts. These threats — along with SGCN vulnerable to the threats — are briefly noted in each of the habitat profiles in Chapter 7. The threats, along with suggested conservation actions to remedy the threats, are described in more detail in Chapter 8: Threats and Conservation Actions.
Climate Change Adaptation and Mitigation Strategies
We decided against an in-depth analysis of potential climate change impacts because this was not deemed cost-effective nor highly valuable at this time. Rather than committing limited resources to assessing individual species’ responses to highly-uncertain variables, AZGFD opted for an approach that would identify the most critical needs and identify immediate actionable strategies. The strategies listed below form a baseline for adaptive planning with the intent of identifying additional conservation targets and modifying our approach as our knowledge of climate change impacts improves. These strategies were adapted from guidelines by the Association of Fish & Wildlife Agencies (AFWA 2009). Recommendations for implementing these climate change adaptation and mitigation strategies can be found for each habitat type described in Chapter 7: Habitat Profiles under the section “Conservation in the Context of Climate Change.”
Conserve a variety of habitats that support healthy populations of fish and wildlife as climate changes
Increasing the number and size of high-quality natural areas boosts the likelihood of preserving native biodiversity simply by providing more overall acreage of suitable quality habitat. With an abundance of quality habitats, biologically-diverse communities may be better able to adapt to changing conditions. As climate-vulnerable habitats become more rare or impaired, such as riparian areas and other aquatic habitats, it will be important to identify and protect climate change refugia to ensure these habitat types persist into the future. Coordinating with land management agencies, non-profit organizations, and landowners to establish priorities is an important initial step. To better meet these challenges, AZGFD will seek to work with city/county planners, local governments, and other partners in protecting riparian areas and aquatic habitats through better management of water resources for consumption or agricultural use.
Restore and maintain diverse habitats to support broad species assemblages
Restoring hydrological and natural fire regimes in areas dependent on these forms of natural disturbance is likely to benefit many of the species that currently occupy these areas, as well as those that may migrate to these areas in response to changing conditions. Focusing restoration efforts on COAs, especially those in habitat types associated with climate-vulnerable SGCN, will expand the network of intact habitat blocks and provide refuge for at-risk species.
Encourage and facilitate strategic planning for the renewable energy industry
With Arizona’s ample sunshine and wind, renewable energy sources from wind and solar energy plants are particularly appealing alternatives to fossil fuels. These renewable energy sources, as well as thermal power energy, are feasible options when site selection adequately avoids high use areas for birds, raptors, and bats, installations don’t disrupt important habitat connectivity areas, and the impact of resulting habitat loss is carefully evaluated. In addition, the effect of associated transmission lines must be evaluated and mitigated. Additionally, all properly-vetted sites that move to construction and energy production must be accompanied by comprehensive wildlife conservation strategies to minimize and/or mitigate wildlife impacts.
Maintain existing and identify new wildlife waters for drought mitigation
AZGFD has several programs to enhance, establish, and maintain water sources for wildlife. This program relies heavily on close coordination with partners such as federal, state, and local governmental landowners, as well as private landowners, on whose land these waters are located. In addition to providing resources to establish or maintain these waters, AZGFD works closely with partners to encourage them to make waters accessible to wildlife. This coordination will become increasingly important in the face of continued climate change. In addition, there is a need to evaluate and prioritize if and where new waters may need to be developed, and to identify natural waters that need added protection or enhancement. As environmental conditions change, and if wildlife populations shift their ranges, the monitoring of surface waters will need to be a priority.
Identify and protect key wildlife corridors for landscape connectivity
This strategy depends on partnerships among agencies, industries, and landowners that have an interest in strategic land use that enables wildlife movement to function in the context of a working landscape. Conducting species movement studies and studies that identify likely future range shifts will help to prioritize protection and restoration efforts. Success in this endeavor will require landscape-scale collaboration where environmental responsibility, economic prosperity, and socio-cultural values are all recognized equally.
Conduct research targeting species and habitat types likely to be vulnerable to climate change impacts
Identifying species and habitats likely to respond poorly to the changing conditions brought on by climate change will provide context for both species’ recovery efforts and prioritization of habitat restoration projects. Research focused on ecosystem-level response to climate variability will guide realignment of management and restoration actions with predicted future conditions.
Collect specimens or samples for taxonomic analysis, genetics, research, and/or disease testing
Although the collection of whole specimens is less common, biological samples are often collected to inform management decisions. Biological samples can be used for a variety of purposes such as evaluating genetic relationships, investigating disease history or prevalence, studying diets, determining population parameters such as pregnancy status, or even tracking exposure to hazardous substances. As the climate changes, AZGFD will continue existing wildlife health surveillance programs, and incorporate additional disease testing as needed to inform management of emerging diseases.
Implement long-term monitoring protocols for vulnerable species and habitats to inform adaptive management
Along with identifying species likely to respond poorly to changing climate conditions, long-term monitoring protocols will provide information on success of both species’ recovery efforts and habitat restoration projects. Data collected during monitoring will inform management and align conservation actions with predicted future conditions.
Monitor and mitigate for introduced/invasive species
As environmental conditions continue to change, introduced invasive species will create additional stress on native wildlife through competition, predation, introduction of pathogens, and other adverse effects to habitats. AZGFD has an active aquatic invasive species program, focused on reducing the impact of these non-native invasive species. It will be necessary to develop and establish more comprehensive monitoring protocols and programs for both aquatic and terrestrial invasive species, and to establish and expand partnerships with other governmental and private partners to control the spread of both aquatic and terrestrial wildlife and plant species.
Establish new wild and/or captive populations of climate-vulnerable SGCN
Evaluate the need to establish new wild and/or captive populations of SGCN species will ensure persistence of the species. These activities would allow for preservation of unique genes to ensure the species can survive in the changing conditions brought on by climate change.