The Yellowstone Wildfires of 1988: What effect did the fires have on the grizzly bear population?
The historic 1988 wildfires, which spanned across the core of the Greater Yellowstone Ecosystem (GYE), burned nearly 793,880 acres of the national park (1.4 million acres in the Greater Yellowstone Ecosystem) and cost roughly $120 million ($260 million in 2021). The 1988 wildfires in Yellowstone consisted of 250 fires; the first fires began in June the park continued to burn through November. Many Americans were left with the reaction that the country's first national park had been destroyed.
Starting in 1972, the National Park Service had revealed a new policy: "let it burn," which allowed natural wildfires – caused predominantly by lightning. The strategy appeared to be moderately successful until 1988. During the summer, there were critical anomalies in comparison to preceding fire seasons. During June, Yellowstone was experiencing extreme drought conditions, notwithstanding the above-normal precipitation experienced during that spring. That summer, by mid-July, fires would destroy 17,000 acres. However, at the end of July, the public opinion was that the National Park Service failed to do its job. The larger fires within the interior of Yellowstone were increasing and uncontrollable. The worst day of the fires was August 20, referred to as "Black Saturday." High winds exasperated and propelled scorching and fast-burning fires across more than 150,000 acres, which doubled the amount of area that had already burned and succumbed to fire activity (Hansen and Krantz, 2008).
Starting in 1972, the National Park Service had revealed a new policy: "let it burn," which allowed natural wildfires – caused predominantly by lightning. The strategy appeared to be moderately successful until 1988. During the summer, there were critical anomalies in comparison to preceding fire seasons. During June, Yellowstone was experiencing extreme drought conditions, notwithstanding the above-normal precipitation experienced during that spring. That summer, by mid-July, fires would destroy 17,000 acres. However, at the end of July, the public opinion was that the National Park Service failed to do its job. The larger fires within the interior of Yellowstone were increasing and uncontrollable. The worst day of the fires was August 20, referred to as "Black Saturday." High winds exasperated and propelled scorching and fast-burning fires across more than 150,000 acres, which doubled the amount of area that had already burned and succumbed to fire activity (Hansen and Krantz, 2008).
"No matter what we would have done, the conditions were such that there were going to be great fires in Yellowstone under any circumstances...they were started by lightning, by outfitters, by woodcutters – we were a perfect set up to burn."
– Bob Barbee
Superintendent, Yellowstone National Park
– Bob Barbee
Superintendent, Yellowstone National Park
Wildfire is both a crucial and multifaceted component for overall stability and health in all ecosystems, particularly the Greater Yellowstone Ecosystem (GYE) (Houston, 1973; Romme, 1982; GYCC, 1988; Romme and Despain, 1989; Despain, 1990; Marston and Anderson, 1991; Turner et al., 1997; Turner et al., 1999). Naturally, there are fire return intervals throughout ecosystems, including the GYE and Yellowstone area. Traditionally, historic fire return intervals are 20-25 years for shrub and grasslands in the Northern Range (Lamar Valley) (Houston, 1973) and 300 years or more for lodgepole pine (Pinus contorta) forests and subalpine whitebark pine stands positioned on the central plateau (Romme, 1982; Romme and Depain, 1989). Interestingly, one of the lesser-known facts about lodgepole pine is that their pine cones are serotinous. This means that they require a fire's heat to open and discharge their seeds (Clements, 1910; Habeck and Mutch, 1973).
On the contrary, whitebark pine may depend on stand replacement fires for its sustained existence into the future. Stand replacement fires that are less severe in the alpine zone may diminish competition from climax species like subalpine fir (Abies lasiocarpa) (Kendall and Arno, 1990; Morgan and Bunting, 1990). However, more importantly, and often denied is the fact that whitebark pine matures exceptionally slowly. Whitebark pine populations can ecologically benefit from fire activity in the long-term; regrettably, during the 1988 fires that ravaged Yellowstone, 28% of the mature, seed-producing pines were lost to fire inside of Yellowstone National Park. This extracted and eliminated critical seed sources for tree regeneration and as a crucial food source for both black and grizzly bears going forward (Kendall and Arno, 1990; Renkin and Despain, 1992).
Moreover, aside from conventional canopy forest cover species, the effects of fire on meadow, shrub, and forest understory communities are less well-understood (Houston, 1973; Turner et al., 1999).
Wildland fires directly influence grizzly bear food sources in various ways. Forbs, grasses, and other undergrowth may respond fairly quickly and immediately thrive post-fire conditions (Houston, 1973; Turner et al., 1999; Wamboldt et al., 2001). Maturing trees and other undergrowth may later shade out these plants. Also, root crops can either be negatively or positively influenced by fire; a handful of variables define this. Berry or fruit-producing shrubs may thrive post-fire if canopy cover is reduced (Martin, 1983; Zager et al., 1983; Holland, 1986). Some berries, like Vaccinium scoparium, may take longer to mend post-severe-fires and burn.
On the contrary, whitebark pine may depend on stand replacement fires for its sustained existence into the future. Stand replacement fires that are less severe in the alpine zone may diminish competition from climax species like subalpine fir (Abies lasiocarpa) (Kendall and Arno, 1990; Morgan and Bunting, 1990). However, more importantly, and often denied is the fact that whitebark pine matures exceptionally slowly. Whitebark pine populations can ecologically benefit from fire activity in the long-term; regrettably, during the 1988 fires that ravaged Yellowstone, 28% of the mature, seed-producing pines were lost to fire inside of Yellowstone National Park. This extracted and eliminated critical seed sources for tree regeneration and as a crucial food source for both black and grizzly bears going forward (Kendall and Arno, 1990; Renkin and Despain, 1992).
Moreover, aside from conventional canopy forest cover species, the effects of fire on meadow, shrub, and forest understory communities are less well-understood (Houston, 1973; Turner et al., 1999).
Wildland fires directly influence grizzly bear food sources in various ways. Forbs, grasses, and other undergrowth may respond fairly quickly and immediately thrive post-fire conditions (Houston, 1973; Turner et al., 1999; Wamboldt et al., 2001). Maturing trees and other undergrowth may later shade out these plants. Also, root crops can either be negatively or positively influenced by fire; a handful of variables define this. Berry or fruit-producing shrubs may thrive post-fire if canopy cover is reduced (Martin, 1983; Zager et al., 1983; Holland, 1986). Some berries, like Vaccinium scoparium, may take longer to mend post-severe-fires and burn.
1989 Preliminary Study on the Effects of Fires on Greater Yellowstone Grizzly Bears
In 1988, 12% of the 4.8 million-ha burned in the Greater Yellowstone Area (GYA), including six national forests, two national parks, two national wildlife refuges, state land, and privately owned land (Schullery, 1989). The following year, in 1989, the IGBST began to examine and ascertain the long-term impact and effects of fires on the grizzly population and individuals.
The binding primary effect of the 1988 fires on the grizzly bear population increased the availability of some food sources (ungulates) in the fall through fire-related deaths. In 1989, researchers (Blanchard & Knight, 1990) documented 56% of 517 revisited aerial radio-relocation sites had not been burned during 1988; 206 sites were burned, 22 could not be located. The known fire intensity at the 206 sites: 59% were classified as light-moderate, 26% were moderate-heavy, and 15% were heavy-intense. During observations, vegetative cover at burned sites was significantly lower than during introductory documentation; live forest cover also dropped and was distinctly reduced by 43% at 151 forested revisited sites burned during 1988. Whitebark pine stands were diminished by a massive 54% at feed sites (this is not to be confused with the 28% of total mature whitebark pines lost throughout the entire park; 54% of whitebark at feed analysis and activity sites were reduced or lost).
During 1989, 40 grizzly bears were actively monitored by the IGBST. Of the 40 grizzlies, 78% of the bears were located and found during all, or sometime during the year inside the fire perimeter (20 females, 18 adults; 11 males, seven adults; five of the 31 were never observed in a burned site). Fig A. shows radio-relocations for female grizzly bears in feed/activity site areas, with the 1988 fire overlay. Preliminary analysis found that all cohorts and groups of bears were most often found in the burned areas during the summer months. During the fall, the majority of bears were located in whitebark pine stands. In the spring months, females with cubs-of-the-year (COY), lone adult females, and males were found and located at burned feed sites less than females with yearlings, two-year-olds subadult females.
In 1988, 12% of the 4.8 million-ha burned in the Greater Yellowstone Area (GYA), including six national forests, two national parks, two national wildlife refuges, state land, and privately owned land (Schullery, 1989). The following year, in 1989, the IGBST began to examine and ascertain the long-term impact and effects of fires on the grizzly population and individuals.
The binding primary effect of the 1988 fires on the grizzly bear population increased the availability of some food sources (ungulates) in the fall through fire-related deaths. In 1989, researchers (Blanchard & Knight, 1990) documented 56% of 517 revisited aerial radio-relocation sites had not been burned during 1988; 206 sites were burned, 22 could not be located. The known fire intensity at the 206 sites: 59% were classified as light-moderate, 26% were moderate-heavy, and 15% were heavy-intense. During observations, vegetative cover at burned sites was significantly lower than during introductory documentation; live forest cover also dropped and was distinctly reduced by 43% at 151 forested revisited sites burned during 1988. Whitebark pine stands were diminished by a massive 54% at feed sites (this is not to be confused with the 28% of total mature whitebark pines lost throughout the entire park; 54% of whitebark at feed analysis and activity sites were reduced or lost).
During 1989, 40 grizzly bears were actively monitored by the IGBST. Of the 40 grizzlies, 78% of the bears were located and found during all, or sometime during the year inside the fire perimeter (20 females, 18 adults; 11 males, seven adults; five of the 31 were never observed in a burned site). Fig A. shows radio-relocations for female grizzly bears in feed/activity site areas, with the 1988 fire overlay. Preliminary analysis found that all cohorts and groups of bears were most often found in the burned areas during the summer months. During the fall, the majority of bears were located in whitebark pine stands. In the spring months, females with cubs-of-the-year (COY), lone adult females, and males were found and located at burned feed sites less than females with yearlings, two-year-olds subadult females.
Annual home range sizes for five monitored bears during 1989 (Table 1) were noticeably smaller than their 1987 ranges. One of the five did have COY in 1989, and it is known that females with COY will have smaller home ranges). Still, however, the other four bears exhibited much smaller ranges. For comparison, I have included female (w/cubs) sightings (Fig. B) and home range information (Table 1.1) from our project (Brasington, 2020) to show the continuation for many of the previously documented and monitored feed/activity sites.
During 1989 feed site examinations, 25% of 390 grizzly bear activity sites examined occurred at burned locations with average fire intensity light-moderate. The most significant frequency and period of use was the early season (June, July, August), which accounted for 18% of total feed sites. However, no signs of feeding activity could be found at 71% of radio locations in burned areas, compared to 46% at unburned site locations. Typical food sources at burned sites included succulent vegetation and roots. Pial seed, ants, and large mammals were most typical at unburned sites.
Through preliminary analysis, there is no evidence to verify that the 1988 wildfires affected feeding and foraging patterns or grizzly bear movements during 1989. Smaller home ranges documented in 1989 are independent of the 1988 fires and most likely a product of food availability and good foraging opportunities. The fires did affect foraging strategies by expanding the availability of carrion during the spring through a decrease of forage on winter ranges for ungulates (elk) (Singer et al., 1989); reducing and eliminating grazing opportunities at some feed sites and enhancing them at others; severely reducing the future opportunity for the use of whitebark pine seed in burned forested areas where whitebark had previously persisted.
During 1989 feed site examinations, 25% of 390 grizzly bear activity sites examined occurred at burned locations with average fire intensity light-moderate. The most significant frequency and period of use was the early season (June, July, August), which accounted for 18% of total feed sites. However, no signs of feeding activity could be found at 71% of radio locations in burned areas, compared to 46% at unburned site locations. Typical food sources at burned sites included succulent vegetation and roots. Pial seed, ants, and large mammals were most typical at unburned sites.
Through preliminary analysis, there is no evidence to verify that the 1988 wildfires affected feeding and foraging patterns or grizzly bear movements during 1989. Smaller home ranges documented in 1989 are independent of the 1988 fires and most likely a product of food availability and good foraging opportunities. The fires did affect foraging strategies by expanding the availability of carrion during the spring through a decrease of forage on winter ranges for ungulates (elk) (Singer et al., 1989); reducing and eliminating grazing opportunities at some feed sites and enhancing them at others; severely reducing the future opportunity for the use of whitebark pine seed in burned forested areas where whitebark had previously persisted.
2002: Effects of Wildfire on Vegetal Grizzly Bear Foods in the Greater Yellowstone
The compilation of data through visiting bear-used feed/activity locations post-fire may be used to model food abundance fluctuations against time since the latest disturbance. Such models can be explicitly used to inform management decisions to determine the abundance of bear foods following various management prescriptions (Podruzny et al., 2003). Because of the considerable uncertainty surrounding so many grizzly bear food sources (invasive species on Whitebark pine (Kendall and Arno, 1990), cutthroat trout (Schullery and Varley, 1996), human and other predator impacts on ungulate populations), the availability of these foods cannot be guaranteed. Vegetal foods would become increasingly more significant and essential to grizzly bears in the absence of any or all of these notable food sources. While scientists acknowledge fire as a primary origin of disturbance for many grizzly foods, the ecological benefits must be considered. We attempt to develop a better comprehension and awareness of how bears react over time to fire (loss of some food sources), which will help us secure better recognition of how fire management activities truly impact and affect grizzly bears.
In 2002, the IGBST assessed the potential of developing measures of change in bear foods post-succession by revisiting a sample of original sites sampled following the 1988 fires. Crews revisited [random] 55 of 479 points and repeated the original sampling methods outlined by Blanchard (1985) and Mattson et al. (1991).
The compilation of data through visiting bear-used feed/activity locations post-fire may be used to model food abundance fluctuations against time since the latest disturbance. Such models can be explicitly used to inform management decisions to determine the abundance of bear foods following various management prescriptions (Podruzny et al., 2003). Because of the considerable uncertainty surrounding so many grizzly bear food sources (invasive species on Whitebark pine (Kendall and Arno, 1990), cutthroat trout (Schullery and Varley, 1996), human and other predator impacts on ungulate populations), the availability of these foods cannot be guaranteed. Vegetal foods would become increasingly more significant and essential to grizzly bears in the absence of any or all of these notable food sources. While scientists acknowledge fire as a primary origin of disturbance for many grizzly foods, the ecological benefits must be considered. We attempt to develop a better comprehension and awareness of how bears react over time to fire (loss of some food sources), which will help us secure better recognition of how fire management activities truly impact and affect grizzly bears.
In 2002, the IGBST assessed the potential of developing measures of change in bear foods post-succession by revisiting a sample of original sites sampled following the 1988 fires. Crews revisited [random] 55 of 479 points and repeated the original sampling methods outlined by Blanchard (1985) and Mattson et al. (1991).
Works Cited
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