Firefighters have mostly contained the Bighorn Fire, which has consumed more than 119,000 acres of the Santa Catalina Mountains since a bolt of lightning set the blaze off on the night of Friday, June 5.
The fire was 75 percent contained as of the Explorer’s Monday print deadline. According to fire crews, the Bighorn Fire is almost completely out, with the only active burning taking place in Willow Canyon near the Catalina Highway.
Despite the scale of the fire, firefighters were able to protect the Mount Lemmon community of Summerhaven, which was evacuated on June 16. Over the course of June, residents in some areas of Oro Valley, Catalina, Oracle and the Catalina Foothills were either ordered to evacuate their homes or told to be ready to seek shelter elsewhere.
From the beginning, fire crews had struggled to confine the blaze as the heavy June winds raked it in various directions across steep and dangerous terrain in canyons and up forested hills.
The fire is an ecological catastrophe for the Santa Catalinas. Not only did a large portion of the forest go up in flames, but patches of its landscape may convert to other biomes for decades to come, leaving scrubby clearings where the woods 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,” said 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’s 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 shortly 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.
The devastation from the fire was evidence that the federal government needs to step up with more funding for the Forest Service, according 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.”
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 the National Forest Service, 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.”