Forest Fire Impacts Remain to be Seen
Multiple forest fires raging through Colorado this summer can be measured in numbers of acres and buildings burned, and the risk to human lives, but there is another factor that is harder to measure. Forest fires have a major effect on wildlife.
"The long-term effects of a forest fire on wildlife and wildlife habitat can't be known this soon after a fire," said Ron Zaccagnini, district wildlife manager for the Colorado Division of Wildlife's South Park/Lake George District, which was heavily impacted by the Hayman fire. "It depends on how fast the fire traveled, how hot it was, how quickly the fire changed direction. Often, most wildlife is able to flee a slow-moving fire and some small mammals are able to wait out the fire by staying put in deep burrows."
Many of the latest forest fires -- likely to be remembered as the largest fires in Colorado's recent history -- however, have been very hot and very fast and happened during a time when many animals are tending newborns or still nesting. Wildlife biologists speculated there were a number of individual animals lost in the blaze, particularly young and newborn animals that were unable to travel quickly.
"Larger animals have the best chance of getting out quickly. It's likely that many adult animals were able to escape the fire, but younger ones may have been trapped. We won't be able to enter areas to check on damage until everything has been cooled down," Zaccagnini said. "Adult birds would have been able to fly away, but nests left behind may have held flightless young or unhatched eggs."
Zaccagnini and other wildlife officers have been asked what to do if people find wildlife that may have been displaced by the fires.
"Leave fawns alone, leave wildlife alone, especially young ones. Displaced wildlife will find a new home, or may return to their original range when the fire is over. You may see what appears to be 'not normal' behavior, but it is most likely stress from the event and from being in a new area." Always keep pets away from wildlife, but particularly at this time, as stressed wildlife needs peace and quiet to recover the energy spent to escape from the fire.
"Not all the large animals escaped the Hayman fire," reported Mark Lamb, wildlife manager for the South Park/Fairplay district. "We know of two herds of elk that were caught in the Hayman fire -- with 20 to 30 animals per herd -- that didn't get out. From what we can tell, they escaped one part of fire, but were caught in another danger. The plumes of smoke get so heavy, that when the fire slows down late in day as the humidity changes, the smoke column collapses, and it's like an explosion on the ground. Anything in the area at that point isn't going to survive."
Despite the loss of ground-dwelling small animals, nesting birds and a relatively small number of elk and deer (compared to Colorado's overall populations), biologists remain optimistic about long range effects. "From what I've seen so far, a minimal number of wildlife was lost," Zaccagnini said. "We did lose some individual animals - that's to be expected - but in many places, you can see green islands in the blackened areas of the fire - places that were not burned. These are areas of refuge for wildlife. It appeared that in some spots, the fire left the valleys alone, and jumped from ridgetop to ridgetop. We found that many deer had gone down to the river and survived. We saw a deer with two fawns this morning, walking in an area near the burn."
Once it is safe to return to the site of the fire and look things over, Zaccagnini said, most people would be surprised to discover that a forest fire rarely burns all the trees in an area.
"There will be live trees in pockets that survive the fire, like an oasis. It's not just a big, black skeleton of the forest like people imagine. The Hayman fire's path left a mosaic, I'd estimate that the forest is about 50 to 60 percent burned within the fire boundaries, and there are areas where only the ground cover was burned. There are a few places, however, where it appears as much as 90 percent of an area was burned," Zaccagnini said. "But some animals will return quickly to the area. Terrestrial species will come out okay, or even ahead, following the fire. The biggest problems will be the aquatic environment."
Silt, sediment, ash and soot can overwhelm waterways and make it difficult for fish to survive. With Colorado facing drought conditions even before the fire, unusually low water levels will make it harder for fish to survive debris entering water, as there is little possibility of dilution.
Zaccagnini and other Division of Wildlife representatives will be working with the Forest Service and other agencies on a special team called the Burned Area Emergency Rehabilitation team (BAER). The Natural Resources Conservation Service and State Forest Service are also expected to be instrumental in forest restoration. Using on-the-ground information and fly-overs of the burned area, the team will make an assessment of short-term and long-term damage.
"We'll be creating a plan for reseeding, stabilization and restoration of habitat," Zaccagnini said. "The old age forest will be replaced with a new forest and new growth. The food supply and habitat that was in short supply will be better - we'll probably see an increase in deer and elk in the next few years. Our biggest concern is impact of erosion on water quality."
Eric Odell, a habitat biologist with the Division of Wildlife's Northeast Region, will also be working with the BAER team to determine the best course of action to minimize additional problems as the forest regrows. One of the most difficult challenges occurs after a forest fire is contained. When rains hit a burned-out area, the lack of trees and undergrowth allows water to run off quickly, carrying soil, soot and ashes into drainages. Heavy rains and flooding can erode watersheds and wash sediment into streams and rivers.
One way to control erosion is to seed burned soil with quick-growing grass. In most forest areas, native plants and grasses are preferred or required in any reseeding projects, but native grass usually needs a full year to take root. Planting non-native grasses can displace native plants. Instead, immediately following a fire, managers often re-seed with mixtures of quick-growing annual grasses that will only live for a year and plant slower-growing native seeds at the same time. (The temporary non-native grasses selected are sterile and will not reproduce.) In that first year, these plants help hold the soil and afterwards they die off and make room for native plants.
"While everyone else is wishing for a big downpour to help stop the fires, in order to restore the burned areas we need light rain and we need it to wait a month for ideal conditions," Odell said. "Too much rain too quickly can cause flooding, mudslides and erosion of soil, soot and ash into water drainages."
"But the trick is, we need just enough rain to help sprout the seeds. Often, plants with a fibrous root mass are planted after a fire to hold the soil in place. What happens between now and when re-vegetation takes place is critical. If there is one really big storm - an inch of rain in an hour -and there's nothing there to trap run-off, it can be pretty bad. But, if we get about a quarter-inch of rain in 24 hours, that would be a great help. It would give us time to start some kind of vegetation, and lay down straw mats to slow erosion. Whatever happens next with the rain is going to tell a different story."
Within a year or less, the burned area is likely to become an interesting place to watch as nature rebuilds. Three years after the 1988 Sugarloaf fire in Boulder County, signs of renewal were abundant with plenty of tall snags - dead trees - with woodpeckers and insects. Insects are usually the first to return to a burned-out area, often followed by cavity-nesting birds. By feeding upon dead or dying trees, wood borers and beetles serve as food to species of birds. The dead wood provides ideal habitat for certain birds that will thrive after a fire. Decaying trees attract insects that are fed upon by many species of wildlife.
Today, a dozen years after the fire, the Sugarloaf area is teaming with wildlife. Soon after the fire, there were small mammals, such as voles and deer mice, which provide food for larger predators. A decade later, there are many deer, elk and bear in the area. One of the first plants to grow back was wild raspberries, and the birds returned immediately to eat them.
On a much larger scale, in 1988, the world watched more than one-third of Yellowstone Park burn, and a group of scientists from different disciplines predicted the area might lack vegetation for decades. But to their surprise, the grasses and wildflowers returned the first spring. The North Fork fire, Yellowstone's largest, consumed 531,000 acres, but researchers were surprised to find some flower species, such as lupine, tripled in numbers the following year. Other flowers that grew back quickly in Yellowstone were Indian paintbrush, pine grass flowers and showy asters.
The specific ways in which nature rebuilds a forest depend on many factors, each unique to the specific fire. If the fire was exceptionally hot, the ground may become sterile for several years. Generally, the rich ash and increased sunshine, since mature trees are no longer blocking the sun's rays, provide a place for certain young trees and plants to grow. Some tree species - notably aspen and lodge pole pine - are adapted to grow in post-fire conditions. The pine cones often remain closed for years until they are opened by the heat of forest fires. And trees that don't survive the fire still play an important role in rebuilding the forest, as nutrients that were stored in the living trees have been released into the soil to create conditions prime for new plants to grow.
But we can be sure that the forest will look different for years, as will the wildlife species that move in following the fire. Wildlife that lived in a mature forest may move to another area with the type of tall trees and forage they prefer, and the burned area may attract new species during the growth period. During various stages of regrowth, a variety of wildlife will move in and move out of the same area.
Although the timing of the fire created a greater impact on the bird population than it might have a few months later when young birds were able to fly, it can have a benefit to the overall bird population, too.
"Many birds can nest a second time," said Lamb. "It depends on availability of habitat and nesting sites. We'll also see bird species appear that were more rare in the area before the fire, because it wasn't the type of habitat they prefer. What usually happens after a fire is that the birds that are cavity nesters -- including flickers and other woodpeckers, chickadees, mountain bluebirds, and some nuthatches -- will find places in the dead trees."
"Once it's safe, and fire closures are lifted, people will want to look at the area over a period of time to see the changes that occur," Zaccagnini said. "The fire brings the forest back to an earlier successional stage. In any healthy ecosystem, you need a variety of stages; different ages and types of plants and trees. The most variety of wildlife species can be supported in an ecosystem that has enough of each of the various stages. For wildlife, fire is generally part of a healthy ecosystem -- it's not bad in and of itself."