The Bighorn Fire has devoured more than 81,000 acres of the Santa Catalina Mountains since a bolt of lightning set the blaze off on the night of Friday, June 5. It has spread northeast through the forest of the Catalinas as well as south down the slopes of areas as such Ventana Canyon, filling the skies with smoke and giving Tucsonans a view of flames after sunset.
Despite the size of the fire, firefighters had thus far successfully managed to protect the Mount Lemmon community of Summerhaven, which was evacuated last week. As the fire burns toward the base of the mountain, residents in the Catalina Foothills as well as some areas of Oro Valley, Catalina and Oracle have been warned about possible evacuations, although firefighters believed they were prepared to fight the fire once it gets out of the Catalinas' steep terrain.
From the beginning, fire crews have struggled to confine the blaze as the June winds raked it in various directions. Once 40 percent contained, the fire raced across the mountain ridges and fell back to 33 percent containment as of Tuesday, June 23. The geography of the Catalinas also challenged fire crews; the fire faced Tucson and then Oro Valley at various times as it snaked between the canyons and slopes, escalating toward Mount Lemmon.
Dry conditions, summer heat and heavy winds have made it more difficult to fight the fire, especially on days when the strong gusts have downed the aircraft that are dropping water and retardant from above.
The fire is an ecological emergency for the Santa Catalinas. Not only is a large portion of the forest going up in flames, but patches of its landscape may convert to other biomes for decades to come, leaving scrubby clearings where forests once stood.
"They always have to balance where they're going to route the fire, and they routed it through the forest, not through Summerhaven, of course," says Don Falk, professor in the School of Natural Resources and the Environment at the University of Arizona. "But the ecological impacts are increased by that kind of decision, which is inevitable in areas that have human values."
Those familiar with Catalina Highway's winding route up to Mount Lemmon may have a better understanding of the fire than they realize. As the road ascends from the desert floor to the pine forests, the ecology naturally changes, as does the fire's impact.
"As you start in the desert and go up to the forest, the biomass of fuels increases. But conversely, the flammability of the fuels decreases with elevation; the fuels are pretty much always ready to burn in the desert, whereas it gets cooler and wetter as you go up higher," Falk said. "The fuels are so discontinuous in the Sonoran Desert ecosystem that you don't often get a spreading fire."
According to Falk, the Sonoran Desert is not adapted to fires and is therefore susceptible to more lasting damage. Naturally, large-scale fires are rare in the sparse desert. But invasive buffelgrass, first brought to the desert for cattle food and erosion control, turned our "formerly fire-proof desert into a fire-prone grassland," as the Arizona-Sonoran Desert Museum website explains.
"The Sonoran Desert flora is not adapted to fire," Falk said. "Very few of the desert species have any kind of adaptation to either resisting and surviving a fire, or recovering afterwards. Obviously the poster child for that are saguaros, which are easily scorched and basically have no defenses against fire."
Just above the desert in the valleys of Mount Lemmon are more natural grasslands. These grasses are better adapted to survive fires, as their foliage may burn but their recovery time is quite fast. Going higher, we reach the oak woodlands with chaparral, an area that is also better adapted to fire and which will often resprout in the wake of a major blaze. Finally, atop Mount Lemmon are the pine forests with pinyon and ponderosa pines, which Falk says will not as easily resprout if fire kills them. Instead they invest in heavy bark to resist fires.
The more the fire rises, the longer the recovery time. Grasslands can recover in six months to a year, whereas the oak woodlands can take three to five years. But the pine forests, in a worst-case scenario with a severe fire and damaged soil, can take centuries to fully recover.
"There are two dimensions of fire severity—vegetation and soil—and we really ought to talk about both," Falk said. "After a fire, if the soils are intact, then recovery can proceed. But if the soils are damaged, such as if there's a large erosion event or if the soils become hydrophobic and won't absorb water, then it doesn't matter if you have seeds available from surviving trees, they're not going to grow."
Even if the woods have the opportunity to regrow, it doesn't always happen. Fire ecologists document a phenomenon called "type conversion," where native shrub species can move into burned areas, replacing what was once forest. Eventually trees may move back in, but this process can take decades. Type conversions occurred throughout stretches of Mount Lemmon as a result of the 2002 Bullock Fire and 2003 Aspen Fire.
"Pretty much everywhere you look on the mountain, if you see large areas of shrubland, those were all areas of forest that had high-severity fires and did not recover as forest," Falk said. "That is a dominant trajectory for post-fire ecology. It doesn't go back immediately to forest... When an ecosystem heals, it may turn into something else, and that may be a perfectly natural process that we have to get used to."
There could be another ecological crisis on the horizon: The monsoons are set to begin within weeks and after a fire. Soil is vulnerable because it isn't protected by undergrowth, which can lead to massive erosion and scouring during a summer deluge. This notably happened in the Chiricahua Mountains after the 1994 Rattlesnake Fire.
"You can lose a thousand years of topsoil in a matter of hours," Falk said.
As of this week, nearly 1,000 firefighters and support personnel were on the job, establishing burn lines and streaking retardant around the fire to keep it from further threatening homes.
So far, the firefighters have been able to protect homes and businesses both on the mountain and its foothills.
"One of the big stories from last night is that we were able to get our black line, our burn operation, over even further," said fire operations section chief Travis Mayberry in a June 22 meeting. "We feel very good about the threat level to San Manuel and Oracle being greatly diminished."
On the night of June 21, one of the firefighters protecting the Summerhaven area suffered a "medical emergency" and had to be helicoptered off the mountain to a medical center. Mayberry highlighted the importance of staying in accessible areas for situations like that, which makes fighting the fire in the canyons and steep slopes especially difficult. According to the Arizona Department of Forestry and Fire Management, the only other injuries so far are five minor-heat related illnesses.
Several recreation areas are closed due to the fire, including Catalina State Park, and popular trails including Romero Canyon, Pima Canyon, Finger Rock, Pontatoc, Pontatoc Ridge and Linda Vista.
The terrain has made battling the blaze a challenge.
"Since there are no roads in the area, the tried and true tactic of having brush fire trucks assist the Hotshot crews is not an option to suppress the fire," said Adam Jarrold with the Golder Ranch Fire District. "So, the fire is being attacked primarily from the air. Weather has been a concern because it has been high temps with very low humidity and windy which can increase the fire's intensity and growth."
The windy weather has battered the columns of smoke rising above the Catalinas in different directions, often with multiple changes in the same day. The Pima County Department of Environmental Quality issued an air quality health watch on June 11, warning of elevated levels of particulate matter and ground-level ozone in the areas near the fire and beyond. For multiple days, the smoke spiraled through the Tucson sky, and PDEQ warned children, older adults and those with heart or lung disease to be cautious and understand that "if they can smell smoke, they are breathing smoke."
Fire crews remind the public that drones are prohibited over the fire area, as firefighting aircraft are busy and must be grounded in drones' presence. According to NFS, on June 8 a drone was observed over the Bighorn Fire's southern perimeter, which "forced the aircraft suppression effort to be halted, endangering the lives of on the ground firefighters and the aircrews at a critical time during the height of the burning period." This was the second such incident in three days.
The devastation from the fire was evidence that the federal government needs to step up with more funding for the Forest Service, according the Falk.
"I really think the public agencies do the best they can," Falk said. "This is not the fault of the National Forest Service or the Bureau of Land Management. They are managing the forests, I think the best they can. This is not a case of mismanagement. They are under-resourced and congress has slashed funding. Fighting wildfires now consumes more than half of the entire Forest Service budget every year... We really need to support these agencies more, because fires like this are not only expensive to fight, but some of the effects could be mitigated if they were given the resources they need." ■