Yellowstone Fires of 1988 - Impacts On The Park - Vegetation and Wildlife

Vegetation and Wildlife

The fires in Yellowstone left a mosaic of areas greatly affected and others less so. Inside fire perimeters, large expanses of forest were completely untouched. There were three major types of burning. From an aesthetic viewpoint, the most destructive fires were the canopy crown fires that in many places obliterated entire forests. Crown fires accounted for about 41 percent of all the area that burned. Mixed fires burned both the canopy and vegetation on the ground, or burned one or the other as they spread through the forest. Ground fires spread slowly along the ground, consuming smaller plants and dead plant material; some ground fires burned for longer duration and intensity, contributing to the loss of many trees whose canopies were never directly burned.

The recovery from the fires began almost immediately, with plants such as fireweed appearing in a matter of days after a fire had passed. While surrounding national forests did some replanting and even dispersed grass seed by airplane, the regeneration in Yellowstone was generally so complete that no replanting was even attempted. Though some small plants did not immediately reassume their pre-fire habitats, most did, and the vast majority of plants regrew from existing sprouts which survived the heat from the fires. There was a profusion of wildflowers in burned areas, especially between two and five years after the fires.

Seeds had little distance to travel, even in severely burned areas. Much of the most badly burned forest was within 160 to 650 feet (49 to 200 m) of less affected areas. Still, most regeneration of the plants and trees came from immediate sources, either above or below ground. Lodgepole pines generally do not disperse their seeds more than 200 feet (61 m), so seed dispersal from less burned parts apparently had little effect on more severely burned areas. In regions that did experience complete burnouts, the average depth of charred soil was only about half an inch (14 mm), so few roots, even of grasses, were killed by the fire. This allowed rapid regeneration throughout the ecosystem.

The predominant tree in Yellowstone, the lodgepole pine, fared poorly from the fires, except in areas where the heat and flames were very mild. The lodgepole pine is serotinous and often produces pine cones that remain closed and will not disperse seeds unless subjected to fire. Research of test plots established after the fires indicated that the best seed dispersal occurred in areas which had experienced severe ground fires, and that seed dispersal was lowest in areas which had only minor surface burns. Regions with crown fires sometimes had the highest rates of regeneration of lodgepole pine after 5 years. However, the rate of lodgepole regeneration was not uniform, with some areas seeing extremely high densities of new growth while other areas had less. Stands of dead lodgepole killed by the fires may persist for decades, rising above new growth and providing habitat for birds and other wildlife.

Aspen became more widespread after the fires, occupying areas that had been dominated by conifers. It had long been believed that Aspen regenerated by sprouting from existing roots rather than by seed dispersal. However, Aspen sprouts appeared two years after the fires as far as 9 miles (14 km) from the nearest known Aspen trees. Aspen is a preferred grazing food for elk and many of the newer Aspen are consequently small, except in areas that are harder for elk to get to. The resurgence of Aspen after the fires was a contrast to pre-fire events, as Aspen had been increasingly scarce in the park. This might be a temporary event as conifers continue to grow and eventually crowd out other tree species.

Contrary to media reports and speculation at the time, the fires killed very few park animals— surveys indicated that only about 345 elk (of an estimated 40,000–50,000), 36 mule deer, 12 moose, 6 black bears, and 9 bison had perished. Of 21 grizzlies that were radio-collared and had home ranges where the fires happened, only one was believed to have been lost. Grizzlies were observed in burned areas more often than unburned areas the following year, feeding on the proliferation of roots and foliage as well as on ants which thrived due to all the dead wood. Moose had been declining in the northern sections of the park since the 1960s, but the decline became more obvious after the fires. Unlike elk, which are primarily grazers and tend to eat grasses, moose are more likely to be browsers, consuming primarily woody food sources, particularly willow and subalpine fir, which were temporarily reduced by the fires. All ungulates experienced a high initial mortality the winter after the fires, but this has been attributed to a severe winter more than the fires themselves. However, moose populations, unlike other ungulates, have not rebounded in subsequent years. Rodents likely experienced the highest mortality of all mammals due not only to heat and smoke they could not easily escape, but also because of the reduction in forest cover, allowing would-be predators less difficulty in spotting them.

Approximately 100 dead fish were reported in two streams after fire retardant was accidentally dropped on them. Aside from a temporary decrease in a few species of aquatic insects, no long term impact has been observed on aquatic life in any of Yellowstone's rivers or lakes.

NASA Landsat project scientist Jeff Masek talks about the recovery of Yellowstone and how Landsat satellites detect its burn scars from space. This multi-coloured animation shows the different fires that ignited, combined and spread throughout Yellowstone from Jun. 30 to Oct. 2, 1988. Yellowstone's burn scars.

• The Recovery of Yellowstone National Park (burned areas are red)

• August 5, 1987

• August 23, 1988

• August 2, 1989

• September 15, 2008