Yellowstone National Park forms the core of the Greater Yellowstone Ecosystem. At 28,000 square miles, it is one of the largest, nearly intact temperate-zone ecosystems on Earth.
Many environmental factors affect the health of this dynamic ecosystem. Ecological and geological processes continue to shape the environment as they have for millennia. Human-caused factors also have an influence. Air pollution, climate change, and the introduction of nonnative species have had an impact on natural resources worldwide. Yellowstone provides a place where scientists can study how these trends affect ecosystems, and foster an understanding of what changes we should expect in the future.