The Future Effects of a Variable Climate at Grand Canyon National Park: What Will Tomorrow Bring?

The Future Effects of a Variable Climate at Grand Canyon National Park:

What Will Tomorrow Bring?

By Wayne Ranney

Climate change.

The term crops up everywhere these days—in newscasts, political debates, around the proverbial water cooler at work—it is even brought up in houses of worship as a moral imperative. In our country, the concept of climate change remains controversial. This is not because the scientific community that studies it questions the evidence (they do not). Rather, the controversy lies beyond the realm of science, embodying a legitimate concern that many of the remedies proposed to offset its negative effects will require substantial changes to our energy infrastructure and national economy (or that the predicted consequences are too dire, or that humanity is too small an entity to affect a global-scale system, or is tied up in tribal politics). But the science is clear that our climate is changing and regardless of the cause, we cannot escape its effects by merely bemoaning the inconveniences it may bring to established norms.

For as long as our planet has circled the sun (nearly 4.6 billion years!) Earth’s climate has changed. The geologic record held in rocks and ice holds the evidence for these sometimes slow, sometimes rapid, perturbations in incoming solar radiation, precipitation, and temperature. The problem with humans vis-a-vis climate change is that for most of our existence the science of geology did not exist. Inadvertently perhaps, we developed the mistaken belief that everything we see on Earth today is the way it has always been. Our awareness of the scale of geologic change is a relatively recent development in humanity, and the rapid blossoming of this earthly pulse pushes our species into a deeper awareness of the mutability in all of earth’s natural systems. Our rapidly developing geologic awareness is, in a way, outpacing our sustainability.

Anyone with a deeply held appreciation and love for Grand Canyon National Park will naturally contemplate what the effects of climate change might have in this relatively small corner of our globe. National Park Service (NPS) managers and scientists have been and will continue to monitor the numerous natural systems at work in the park, collecting baseline data that can ultimately show when and where these changes may take place. While all facets of the park’s natural systems will be affected by these changes, there are four areas of critical concern to discuss further:

1) Hydrogeology and water management, 2) Forests and wildfire, 3) Wildlife and invasive species, 4) Recreation and park visitation.

Hydrogeology and Water Management – Without a doubt, the number one area of concern regarding climate change in Grand Canyon National Park is how it may affect the discharge of water in springs within the canyon. The approximately 750 springs in the park provide perennial and seasonal flow to myriad desert streams, life-giving water in an otherwise arid environment for wildlife and visitors, and habitat for rare, endemic, and threatened species. Every one of the six million-plus visitors and the 2,500 full time residents of the park is dependent on a single spring within the canyon for their domestic water—Roaring Springs. Together with the aging infrastructure of the Trans-Canyon Waterline (built in the 1960s), concerns about the future reliability of this spring —and how a decrease in its discharge could affect entire park operations—is the number one priority for park managers.

In the last few decades, a few substantial and highly visible springs in the canyon have gone dry seasonally during extended periods of low winter precipitation (Vasey’s Paradise along the Colorado River and Dutton Springs in the Deer Creek drainage come to mind). These episodes of spring failure helped to bring attention to the ongoing reliance that exists between water discharge from Roaring Springs and the park’s growing and unwavering domestic water needs. A better understanding of Grand Canyon’s subsurface plumbing system has now become a very active avenue of study within the park.

Sustainable water flow in Grand Canyon’s springs originates almost entirely from the amount of winter snow that falls on the two rims. (Spring water also is sourced from storage in the underground aquifer as well as rainwater precipitation, however, neither sources are ultimately sustainable.) This gradually melts and percolates downward through fractures and faults in the rocks, creating a complex natural plumbing system. With an interest in knowing more about the details of how this plumbing system operates, fluorescent dye-tracer studies on the North Kaibab Plateau were initiated in 2015. Non-toxic tracers were allowed to mix with snowmelt and enter sinkholes on the plateau (sinkholes are the recharge areas for inner canyon springs on the north side). The tracers could then be detected as they flowed from multiple inner canyon springs. The results show a complex flow pattern, but most importantly they revealed the transit time for spring water through the rocks. The transit time is a critical component of the studies—if it is found to be too fast then springs may be prone to quicker decreases in spring discharge.

Most climate models (as well as information from tree ring studies) predict that the American Southwest will experience longer and more frequent droughts if the climate warms. Taken together with the results of the dye-tracer studies, this indicates that relying exclusively on a single spring for the park’s entire domestic water supply may be overly optimistic with respect to long-term future reliability in water delivery. A decrease or elimination of snow levels on the Kaibab and Coconino plateaus will necessarily cause a decrease in the discharge for many, perhaps even all, inner canyon springs.

Therefore, park managers are considering modifications to the configuration of the new Transcanyon Waterline as the park reconstructs the pipeline due to its age and disrepair. One option is to capture water from Bright Angel Creek near Phantom Ranch, rather than continue to harvest it from Roaring Springs. Alternatively, the park could continue to use Roaring Springs as a water source, while considering a series of water saving measures including water conservation, water reuse, and additional water capture by other means. Meanwhile, park scientists and collaborators are continuing to refine their knowledge of the sustainability and ultimate source of spring water in the canyon. On many different fronts, park managers are aware of and responding to the evidence and the observed trends related to water sustainability. Water management as it relates to spring water in Grand Canyon National Park is one of the top management priorities related to climate change. Forests and Wildfire – The health of Grand Canyon’s forests may be one of the more visible impacts of climate change that is readily apparent to visitors and residents. Perhaps coming as surprising to some, one third of the national park’s acreage (or about 400,000 acres) is covered in forest, including the pinyon-juniper woodland, Ponderosa pine, and mixed-conifer. Predicted dryer and warmer conditions will certainly impact the distribution of these species, with each community being stressed at their lowermost elevations. Extended droughts are also responsible for changes in how fire behaves.

125 years of fire suppression have created overgrown conditions in forests that cause trees to grow too densely together. When natural or human-caused fires encounter these densely grown forests, they may climb a “ladder” of variably aged trees into the forest crown, killing trees that normally are resistant to fire. Just prior to the turn of the millennium, a crisis in forest health was diagnosed and managers moved to reintroduce fire (as well as mechanical forest thinning) into the ecosystem. You have likely encountered the slash piles of woody debris stacked in the forest along the South Entrance Road toward Grand Canyon Village.

Other causes of tree mortality are also on the increase. Since the turn of the millennium at least two beetle infestation events have resulted in significant tree mortality that have thinned out pinyon pine populations in northern Arizona. A close relationship exists between beetle-kill infestations and drought—when pine forests become stressed by drought, the trees do not develop enough sap, which is what normally repels beetles from boring into the trees’ living cambium layer. Although the beetle is what specifically kills the trees, it is merely the messenger in this instance. The underlying cause for much of the recent pine tree mortality is drought.

Chris Marks, Deputy Fire Management Officer at Grand Canyon National Park, has been observing the forest here for over 17 years. When he first arrived in the park, there were no large-scale thinning projects underway to promote forest health. “It became apparent however, that restoring healthy forests in the Ponderosa pine community required the reintroduction of fire into the ecosystem,” he stated. He added that since his arrival, the NPS has been able to return about 70 percent of this community back to near-natural conditions (defined as forest conditions that closely resemble those existing just prior to Anglo settlement). “Essentially, I am working myself out of a job,” he joked.

Since about 1998, nearly every acre of Ponderosa pine forest in the national park has experienced at least one fire. The areas that have experienced multiple fires belong to the 70 percent of forests that have been restored. The other 30 percent have experienced only one fire during that time or still have too many trees or burnable fuel, and so are not yet restored to a satisfactory degree. The NPS is keen on returning as much of this community as possible to a condition similar to pre-settlement conditions.

When thinking about forests at Grand Canyon, it is the Ponderosa pine and mixed-conifer forests located on Grand Canyon’s North Rim and Kaibab Plateau that may come to mind. Here, large stands of Ponderosa pine grow between elevations of about 6,500 and 8,000 feet. The mixed-conifer forest is found at higher elevations on the Kaibab Plateau, rising to about 9,200 feet outside the park in the Kaibab National Forest. This forest is composed of blue spruce, Douglas fir, white fir, and Engelman Spruce. Because two different agencies with differing missions manage resources on the North Kaibab Plateau, an Interagency Fire Management Organization was created to cooperate in the management of this single ecosystem. Through time, the boundary between the national forest and national park, which has been discernable from space photographs because of past management practices, will become less obvious and more blurred.

Fire managers have allowed fire to be reintroduced throughout much of the North Kaibab forest. On the Walhalla Plateau, a mosaic of forest conditions now exists thanks to the restorative properties of fire. Climate change and the threat of extended drought, however, could alter this balance which managers view as mimicking “pre-settlement conditions.” Marks has also observed that fire behavior and tree resiliency itself may be changing. In the past, even low to moderate intensity fires would cling to the forest floor and merely clear out and “clean up” the forest fuels. Now however, even low intensity fires may have the capacity to negatively impact forest health. Low moisture content and persistent drought stress within the trees may be the cause of this surprising development.

Fires throughout the western U.S. are becoming hotter and more intense. Fire season is becoming longer. Trees are less able to fend off the effects of fire and forests are becoming less resilient as well. The very structure of our forests is undergoing change. Wildlife and Invasive Species – Another visible manifestation of climate change in Grand Canyon National Park can be observed in the changes already brought to bear in the park’s wildlife distributions. Indeed, a significant change occurred in the late 1990s when American bison (Bison bison) left the semi-arid grasslands of the House Rock Valley for the cooler and more forested areas of the North Kaibab Plateau. The bison were first brought to the area in 1906 by Charles “Buffalo” Jones, a rancher who in the mid-1880s developed an interest in preserving the once vanishing species. The bison were later cross bred with cattle in a failed experiment to breed a tamer type of buffalo, called cattalo. Today’s herd still retains some genetic markers of the cattle experiment, although they look and behave like full-blooded bison.

When the Kaibab Plateau was declared the Grand Canyon Game Preserve in 1906 by President Teddy Roosevelt, Jones brought 87 bison including three bulls to the new preserve. In 1927, the Arizona Game and Fish Department purchased the herd and moved them to the southern House Rock Valley (today’s House Rock Wildlife Area). They remained there until the late 1990s when a change in herd management, combined with nearby wildfires, allowed some of the animals to migrate upslope to the forested plateau. For about 10 years, the animals migrated between the forested uplands (to feed) and the House Rock Valley (to calve their young). Since 2009 however, they have remained year-round on the plateau.

Although a few recent studies have concluded that bison are native to eastern and northern Arizona, it must be noted there were none described from Arizona at the time of settlement and any prior populations were limited to only a few animals and it is unlikely that large herds of bison were ever a part of this ecosystem. The bison on the plateau have wreaked havoc on the meadows and springs in the forest and park managers are in the process of gradually reducing the number of animals allowed to remain here.

Changes in temperature and precipitation affects other wildlife populations as well. Under warming temperatures and decreased precipitation, female bighorn sheep (Ovis canadensis) may tend to migrate to higher elevations above the river, resulting in increased interactions with humans on the rim. If this occurs, mountain lions (Felis concolor) may encounter female bighorn sheep with much greater frequency and impact the population. This possibility, however, must be contrasted with the idea that bighorn sheep may be too closely tied to their preferred habitat along the Colorado River and the food resources they rely on within the canyon. These contrasting possibilities will cause managers to develop adaptive management techniques, rather than any one predetermined management scheme.

There are so many species of animals within Grand Canyon National Park, it boggles the mind to think about how climate change might adversely affect all of the possible interactions within and between species. One of the biggest concerns is how invasive species—those species not yet present in the park—could enter and disrupt the current ecosystem. In the last few years, javelina or collared peccary (Pecari tajacu) have been observed in Grand Canyon Village and in Waldron Basin along the Hermit Trail. These animals, with their poor eyesight and protective instincts, have a reputation of forcefully fending off perceived threats. Should they “discover” the deeper parts of the Grand Canyon, their range may expand greatly and wreak havoc to inner canyon vegetative communities. Two sightings of coatimundi (Nasua narica) are already known from Grand Canyon. These close relatives of racoons are found mainly in South and Central America but have been moving out of Mexico and southern Arizona recently.

Invasive apprehensions are not limited to vertebrate animals either. Today the park managers are concerned about the introduction of quagga mussels (Dreissena bugensis) in the Colorado River and its tributaries. Native to a single river system in the Ukraine, they were first reported in the Great Lakes region in the 1980s. These rapidly growing invaders encrust and clog pipes, boat engines, and shorelines. They have already invaded the waters of the Powell reservoir north of Grand Canyon and a few individuals have been spotted in some back eddies below Lees Ferry. Fortunately, however, the water temperature of the Colorado River as it exits Glen Canyon Dam and downstream water turbidity may work in favor of limiting their expansion within the national park. Should the Colorado River become warmer however, due to climate change, their expansion may allow them to invade the park’s river and streams.

Recreation and Park Visitation – As it relates to the human environment, climate change could impact the way in which we interact with Grand Canyon’s natural systems. A warmer and dryer environment may cause springs on the canyon’s south side to dry up completely. These springs are already small compared to some on the north side, where more abundant precipitation makes for larger springs. Today, hikes on the popular Tonto Trail are limited to a certain degree to the spring melt season, when otherwise dry drainages experience seasonal discharge. Hiking along this 92-mile scenic platform would cease entirely if perennial springs such as Grapevine, Garden, Horn, Monument, Hermit, and Boucher were to disappear entirely. Diminished flows in the Colorado River are another concern, which may cause for more rocky runs in the canyon’s famous rapids.

The decrease in spring water discharge within the canyon and an increase in wildfire danger may have significant impacts on the public’s ability to visit the canyon entirely or portions of it. The park has already experienced road and trail closures on the North Rim due to the Warm Fire (2006) and the Fuller Fire (2016). Grand Canyon Village has developed evacuation protocols in the event that a large, catastrophic fire moves toward the village. There are only two ways out of the Village creating a concern for residents and visitors alike.

NPS photo by Michael Quinn

Summary – There is little doubt that Grand Canyon is already experiencing some of the effects of climate change. And as the future unfolds, these changes could intensify and continue to stress the park’s natural and human resources. Jeanne Calhoun, the NPS Division Chief of Resource and Science Management at Grand Canyon National Park, asserts that Grand Canyon National Park is preparing for a changeable future. “We know changes are coming and although we cannot entirely predict them, we can monitor many of our natural systems and become better prepared,” said Calhoun. The park is exploring programs that the public will likely welcome in the near future. Rainwater harvesting is one such change that may be coming soon to the park’s many rooftops. An increase in solar power generation may also be one of the more visible tools that could lessen the park’s exorbitant electric bill (the greater portion of which comes from the pumping of water to the South and North Rims). “The challenges are great,” Calhoun said, “but we are excited to meet them with the tools and resources available to us.”

After all, positivity in the face of such challenges has always been the hallmark of those lucky people who come under the spell of Earth’s grandest canyon.