ECOSYSTEM The Greater Yellowstone Ecosystem, with Yellowstone at its core, is one of the largest nearly intact temperate- zone ecosystems on Earth. Greater Yellowstone Ecosystem At 3,437.5 square miles (8,903 km2),Yellowstone As development throughout the West increased, National Park forms the core of the Greater the 2.2 million acres (8,903 km2) of habitat that now Yellowstone Ecosystem—one of the largest nearly compose Yellowstone National Park became an intact temperate-zone ecosystems on Earth. Greater important sanctuary for the largest concentration of Yellowstone’s diversity of natural wealth includes wildlife in the lower 48 states. the hydrothermal features, wildlife, vegetation, lakes, The abundance and distribution of these animal and geologic wonders like the Grand Canyon of the species depend on their interactions with each other Yellowstone River. and on the quality of their habitats, which in turn is the result of thousands of years of volcanic activ- Heart of an Ecosystem ity, forest fires, changes in climate, and more recent Yellowstone National Park was established in 1872 natural and human influences. Most of the park primarily to protect geothermal areas that contain is above 7,500 feet (2,286 m) in elevation and un- about half the world’s active geysers. At that time, the derlain by volcanic bedrock. The terrain is covered natural state of the park was largely taken for granted. with snow for much of the year and supports forests Quick Facts Space and Ownership • Managed by state governments, Management Challenges • 12–22 million acres; 18,750– federal government, tribal • Climate change 34,375 square miles (Sizes, governments, and private • Invasive species boundaries, and descriptions of any individuals • Managing an ecosystem across ecosystem can vary.) Wildlife political boundaries • States: Wyoming, Montana, Idaho • One of the largest elk herds in • Land use change • Encompasses state lands, two North America national parks, portions of five • Largest free-roaming, wild herd of • In Yellowstone: national forests, three national bison in United States − Bison management wildlife refuges, Bureau of Land • One of few grizzly populations in − Grizzly bear management Management holdings, private and contiguous United States tribal lands. − Native fish conservation • Rare sightings of wolverine and lynx − High visitation Greater Yellowstone Ecosystem 53 dominated by lodgepole pine and interspersed with the Yellowstone Plateau itself is a result of uplift due alpine meadows. Sagebrush steppe and grasslands on to hot-spot volcanism. Today’s landforms even influ- the park’s lower-elevation ranges provide essential ence the weather, channeling westerly storm systems winter forage for elk, bison, and bighorn sheep. onto the plateau where they drop large amounts of snow. Influence of Geology The volcanic rhyolites and tuffs of the Yellowstone Geological characteristics form the foundation of Caldera are rich in quartz and potassium feldspar, an ecosystem. In Yellowstone, the interplay between which form nutrient-poor soils. Thus, areas of the volcanic, hydrothermal and glacial processes, and park underlain by rhyolites and tuffs generally are the distribution of flora and fauna, are intricate. The characterized by extensive stands of lodgepole pine, topography of the land from southern Idaho north- which are drought-tolerant and have shallow roots east to Yellowstone probably results from millions of that take advantage of the nutrients in the soil. years of hot-spot influence. Some scientists believe In contrast, andesitic volcanic rocks that underlie the Absaroka Mountains Billings ! are rich in calcium, mag- ! !Livingston ECOSYSTEM Bozeman nesium, and iron. These MONTANA minerals weather into soils that can store more Custer water and provide better Gallatin National Forest !Red Lodge nutrients than rhyolitic National Forest soils. These soils support !Gardiner !Cooke City more vegetation, which Beaverhead-Deerlodge adds organic matter and National Forest Yellowstone National Park enriches the soil. You can Red Rock Lakes ! see the result when you National Wildlife Refuge West Yellowstone ! drive over Dunraven Pass Shoshone Cody National Forest or through other areas of Caribou-Targhee the park with Absaroka National Forest rocks. They have a more John D. Rockefeller, Jr. diverse flora, including Memorial Parkway mixed forests inter- Camas National Wildlife Refuge spersed with meadows. Rexburg Grand Teton ! National Park Lake sediments deposited WYOMING during glacial periods, National Elk Refuge such as those underlying ! ! Idaho Falls Jackson Hayden Valley, form clay Bridger-Teton soils that allow meadow IDAHO National Forest communities to out- compete trees for water. Grays Lake National Wildlife Refuge The patches of lodgepole !Pocatello pines in Hayden Valley grow in areas of rhyolite rock outcrops. Because of the influ- Continental Divide Bureau of Land Management Fish and Wildlife Service ence rock types, sedi- Rivers and Lakes 0 50 Kilometers Forest Service ments, and topography State Boundary North National Park Service have on plant distribu- 0 50 Miles State Land l tion, some scientists The Greater Yellowstone Ecosystem. Description of an ecosystem’s size, boundaries, theorize that geology and characteristics can vary greatly. also influences wildlife 54 Yellowstone Resources and Issues Handbook, 2019 distribution and movement. Whitebark pine nuts are in Yellowstone typically peak in spring rather than an important food source for grizzly bears during au- summer, indicating that human influences are less tumn. The bears migrate to whitebark pine areas such significant than changes in atmospheric circulation as the andesitic volcanic terrain of Mount Washburn. and lengthening daylight. Nonetheless, in addition to Grazing animals such as elk and bison favor the potentially causing respiratory problems in people, park’s grasslands, which grow best in soils formed by ozone levels during the growing season may be high sediments in valleys such as Hayden and Lamar. The enough to prevent sensitive species, such as aspen, many hydrothermal areas of the park, where grasses from reaching full growth potential. and other food remain uncovered by snow, provide sustenance for animals during winter. Sources of Particulate Matter The largest source of particulate matter in Greater Yellowstone is smoke from wildland fires, which is Air Quality ECOSYSTEM The Clean Air Act Amendments of 1977 designated considered part of the area’s “natural background Yellowstone and Grand Teton among the 156 na- conditions” and is taken into consideration in estab- tional parks and wilderness areas that are Class I air- lishing the threshold for “good” visibility. Emissions sheds, requiring the most stringent air-quality protec- from prescribed fires have been relatively insignifi- tion within and around their boundaries. Yellowstone cant. Because of prevailing winds, Wyoming oil and and Grand Teton are in compliance with federal air gas development has not had a detectable effect on quality standards for human health. However, air- air quality in Yellowstone. quality trends may be affecting other aspects of the ecosystem. Even at relatively low levels, such as those Soundscapes found in the Greater Yellowstone Ecosystem, air pol- The Greater Yellowstone Ecosystem has many bio- lution and the subsequent deposition of pollutants logical sounds with important ecological functions in water and soil can leach nutrients from the Earth, for reproduction and survival. Birds, mammals, am- injure vegetation, and acidify and over-fertilize lakes phibians, and insects often need to hear or produce and streams. sounds to attract mates, detect predators, find prey, The thin soils, sparse vegetation, short growing and/or defend territories. The occurrence of sounds seasons, and snow-based water supply of these high in a particular area forms the soundscape. elevation areas limit the amount of nitrogen that plants The natural soundscape of the Greater can effectively use. These conditions make the area Yellowstone Ecosystem delights visitors during the more vulnerable to the effects of acidification and fall elk rut, during birds’ spring choruses, along nutrient enrichment from nitrogen deposition. For rushing streams, and in the still and profoundly quiet example, nitrogen in precipitation has increased at days and nights of winter. Natural soundscapes are a many western sites as a result of fertilizer use and feed- resource and are protected by National Park Service lots. Although nitrogen is a nutrient needed for plant policies. Many park visitors come to national parks growth, too much nitrogen disrupts native plant com- to enjoy serenity and solitude and expect to hear munities that are adapted to low-nitrogen conditions; sounds of nature. Sounds associated with human high nitrogen levels can advance the spread of nonna- activity, including road traffic, aircraft, and snowmo- tive species that increase fire frequency. Acidification biles, often impact these natural soundscapes and are of high-alpine lakes from sulfur and nitrogen deposi- a source of growing concern. Aircraft noise, which tion can cause the loss of macroinvertebrates and fish. is the most widespread human-caused sound in the Long-term changes in the composition of algae in park, is heard on average for less than 10 percent of several alpine lakes in Yellowstone and Grand Teton the day. Yellowstone and Grand Teton national parks are correlated with increased nitrogen.