More recently, human-caused factors such as air and water pollution and non-native species have had a significant impact on natural resources-both here and worldwide. The further impacts on the park of ten million human visits each year are only just beginning to be measured and mitigated. Scientists are striving to better understand these impacts on the park's ecosystem. Park staff carefully monitor threats such as air pollution and destructive non-native species and endeavor to implement proactive measures to preserve the park's valuable resources.
Did You Know?
More than 240 species of birds have been found in the park. Sixty species are year-round residents. Nearly 120 species breed in the park, including 52 species from the neo-tropics. Many other species use the park as an important stopover and foraging area during their semiannual migration.