Yellowstone National Park
Biology and ecology

Yellowstone National Park is the centerpiece of the 20 million acres (80,940 km; 31,250 sq mi) Greater Yellowstone Ecosystem, a region that includes Grand Teton National Park, adjacent National Forests and expansive wilderness areas in those forests. The ecosystem is the largest remaining continuous stretch of mostly undeveloped pristine land in the contiguous United States, considered the world's largest intact ecosystem in the northern temperate zone. With the successful wolf reintroduction program, which began in the 1990s, much of the original faunal and floral species known to inhabit the region when the first explorers entered the area can be found there. The site is home to a key field observation site for the National Ecological Observatory Network.
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