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What is the Greater Yellowstone Ecosystem?

The Greater Yellowstone Ecosystem (GYE), with Yellowstone’s 2.2 million acres at its core, comprises 34,375 square miles (covering parts of Wyoming, Montana and Idaho) and is one of the largest nearly intact temperate-zone ecosystems on earth. Its diversity and natural wealth includes half the world’s active geysers, the largest free-roaming, wild herd of bison in the United States, one of the largest elk herds in North America, one of the few grizzly populations in the contiguous United States, and unique geological interplay between volcanic, hydrothermal, and glacial processes, and the distribution of flora and fauna. Most of the park is above 7,500 feet (2,286 m) with snow covering the terrain most of the year. The terrain supports forests dominated by lodgepole pine interspersed with alpine meadows, and sagebrush and grasslands on the park’s lower-elevation northern range provide essential winter forage for elk, bison, and bighorn sheep.

Yellowstone Resources and Issues Handbook, 2016 - USPS

Geological characteristics for the foundation of the GYE, with geological hot spots influencing the various landforms in the park which in turn influences the weather, channeling westerly storm systems onto the Yellowstone plateau where they drop large amounts of snow. The volcanic rhyolites and tuffs in Yellowstone are rich in quartz and potassium feldspar, which form nutrient-poor soils. However, lodgepole pine that are drought tolerant and have shallow roots can thrive in this soil. In contrast, andesitic volcanic rocks that underlie the Absaroka Mountains are rich in calcium, magnesium, and iron. These soils store more water and provide better nutrients supporting more vegetation, which adds organic matter, enriches the soil and allows for more diverse flora, including mixed forests interspersed with meadows. It is believed that the diverse geology influences wildlife distribution and movement respective to food source location.


The headwaters of seven great rivers are located in the GYE and provide the resources for plant and wildlife habitat, scenic vistas, and recreational opportunities and drives the complex geothermal activity in the region that fuels the largest collection of geysers on earth. In Yellowstone alone, more than 600 lakes and ponds (150 of which are named, 45 have fish) comprise approximately 107,000 surface acres. Some 1,000 rivers and streams make up approximately 2,500 miles of running water.


Yellowstone Lake is the largest high-elevation lake (above 7,000 ft) in North America, covering 286 square miles (12,000,000 acre-feet of water). It is fed by more than 141 tributaries, but only one river. Its greatest depth is 430 feet (131 m) and has an average depth of 138 feet. Yellowstone Lake is undergoing extensive conservation efforts to rid it of lake trout which were illegally introduced to Yellowstone Lake and have jeopardized the survival of the native population of cutthroat trout.

The Yellowstone River is 671 miles long making it the longest undammed river in the lower 48 states. It exits Yellowstone Lake at Fishing Bridge, and continues north-northwest until it leaves the park near Gardiner, MT. From there it continues north and east through Montana and joins the Missouri River just across the North Dakota state line. (Source: U.S. National Park Service).

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