AZGFD release and good synopsis:
Wildfire History and Ecology
Except for changes in climate, wildfires probably had the largest single impact in shaping the ecology of the Colorado Plateau prior to Euro-American settlement. Whether lightning-caused or started by native peoples, wildfires were once quite common occurrences throughout the grasslands and forests of the Colorado Plateau. Major consequences of these frequent fires were the maintenance of an open forest structure in the region's middle-elevation forests, the prevention of tree encroachment into mountain meadows and grasslands, and in some areas the replacement of forested land with grassland or savannah.
Prior to white settlement, studies indicate that fires likely burned through the Plateau's extensive pinyon-juniper woodlands every 10-30 years, through the region's ponderosa pine communities every 2-10 years, and through mixed-conifer forests every 5-25 years. The much wetter and cooler spruce-fir forests atop the highest mountains and plateaus of the region probably went 150 years or more between fires.
The historic fire regimes changed dramatically with Euro-American arrival and settlement. Grazing removed much of the grassy fuels that carried frequent, surface fires; roads and trails broke up the continuity of forest fuels and further contributed to reductions in fire frequency and size. Because settlers saw fire as a threat, they actively suppressed it whenever they could. Initially, fire suppression was very successful because of low fuel loadings; but without fires to consume them, fuels have accumulated over time.
The continuing threat of fire led to an approximately 100-year history of fire suppression policies by land management agencies such as the United States Forest Service. These efforts have resulted in far less frequent fires, disrupting the natural cycles of the region's forests and resulting in many damaging ecological effects. Forests with historically frequent, low-intensity fires were those initially most affected. Pinyon-juniper woodlands, ponderosa pine forests, and drier mixed conifer forests shifted from a fire regime of frequent, surface fires to one of stand-replacing, high-intensity fires.
Fire suppression has contributed to the buildup of organic materials (fuels) on the forest floor. Logging has added heavy fuels in the form of limbs, treetops, and cull logs. In some areas, these heavy fuels have been removed by slash disposal (fuel treatment), prescribed fire, or firewood collection.
By the early 1900s, fire exclusion began altering forest composition and structure. The disruption of natural fire regimes has decreased the diversity of forested areas across the landscape. Frequent fires once killed conifer seedlings encroaching into forest meadows, maintaining numerous open parks in the region's highlands. Fire exclusion permits this encroachment, and meadow acreage has decreased significantly. Establishment of young trees in older stands has provided a fuel ladder for carrying fires into the canopy. With more stand-replacing fires, average stand age is reduced; the diversity inherent in old stands is lost.
Because of heavy fuel accumulations, fires that occur now are more intense and more difficult to contain. Certainly there are more larger fires and more catastrophic crown fires today than historically. On Southwestern forests, the number of fires burning more than 10 acres has increased each decade since the 1930's. The average size of fires since the 1970s has ranged from 14 to 16 acres per fire, double the average size of fires in the earlier decades of the 1940s to 1960s.
Rodeo-Chediski Fire
Impacts on Wildlife
It is important to note that ponderosa pine and pinyon-juniper habitats, and their associated wildlife populations evolved with fire – but typically smaller, more localized fires. However, these habitats and wildlife did not evolve with such fast-moving catastrophic events such as the Rodeo-Chediski Fire.
The ponderosa pine and pinyon-juniper habitats are home to around 268 species of wildlife ranging from whiptail lizards and big brown bats to elk and deer.
Wildfire impacts on wildlife can be both negative in the short term, and positive in the long term, depending on a number of factors. Typically, larger mammals such as deer, elk, bear and lion will move out of the path of a fire – depending on how fast the fire moves. We say typically – but this is not a typical fire. These fires moved fast. Whether or not that resulted in increased wildlife mortality, we can only speculate.
Most wildlife pushed out (or underground) by a fire will move back into the burn area once the active fire passes. We do know that elk especially have already been seen in burned over areas. Whether the wildlife stay is dependent on available food, cover and water.
Many smaller mammals and most reptiles will burrow underground. Their ability to survive the fire, at least initially, is dependent on how hot the fire burns. With many fires, burrowing into the earth even six inches will protect animals from fires reaching up to 3,000 degrees. It is possible that a fast-moving fire might have “baked” the earth less, resulting in good survivability of the wildlife that burrow to escape fire.
Rabbits, birds and other small animals have also been seen in the burned over areas.
This is also the time of year when there is a host of newborn wildlife, such as elk calves and deer fawns, are on the ground. With a fast-moving fire, it is possible that there was high newborn mortality, especially for the larger mammals. However, due to the drought, elk calf and deer fawn crops were exceptionally low this year.
This is also the bird-nesting season. Undoubtedly, most of those nests have been lost, although the adult birds most likely flew away from the fire.
Fire can be a boon or bane for native fish populations. A large-scale fire will sometimes result in fish-killing slurry when hard rains follow the flames. The rains will wash burned materials, as well as now exposed soil, into drainages and this can scour out both native and nonnative organisms. However, such scouring could also set up good conditions for reintroducing native fish. An example is the Dude Fire when native Gila trout were reintroduced into Dude Creek.
Ambient heat from raging wildfires can raise water temperatures to lethal levels for fish. After a fire, the lack of canopy could drastically result in water temperatures rising beyond fish tolerances for fish growth, spawning or even survival.
However, sediments washed into major impoundments can provide a nutrient surcharge to those waters for growing fish. That happened with the Lone Fire when the ash and other sediments washed into Apache, Canyon and Saguaro lakes.
Those are simplified, short-term impacts.
In the long term, some fires can be beneficial to wildlife populations. If a fire burns in a mosaic or patchwork pattern – leaving parts of the forest untouched – a host of wildlife species will eventually benefit once there is sufficient rain for plants to grow.
As a rule of thumb, climax stage mature vegetation does not necessarily provide a wealth of food sources for a diverse number of wildlife, although some species are dependent on older age class forests. New growth can be very high in nutritional value.
Now it is up to Mother Nature. If we get rain, there will be a tremendous green up in the burn area. Studies have shown that the grasses and forbs that grow in burn areas are exceptionally high in nutrition. If there is no rain, they there could be significant delayed wildlife mortalities.
