Species invasions in the United States National Parks: Is the Park Service achieving its mission?

Background/Question/Methods

Many natural areas managed by the United States National Park Service were established to protect native species and historical (but living) landscapes and scenery, and for providing public enjoyment of the same, as long as the natural area remained “unimpaired for future generations.”  A forty-fold increase in global trade and transportation may provide the most significant challenge to Park Service management: the accelerated invasion of alien plants, animals, and diseases into ‘protected areas’. I evaluated case studies of invasions since two landmark papers on invasive species in national parks (from Houston and Schreiner 1995, and Drees 2004). Several populations of invaders were seen as potential problems in 1995 (e.g., invasive goats, wild pigs, burros, etc.). In 2004, it was estimated that 1.1 million ha of the 34 million ha managed by the National Park Service were infested by alien plants and animals. I asked two questions. Are we better off or worse off since those case studies were first reported? And, Is the Park Service achieving its mission?

Results/Conclusions

Our 2009 study reported alien plant species infestations covering 7.3 million ha in 218 national parks. Some invader populations have been successfully contained (e.g., burros in Bandelier N.M., goats in Haleakala N.P.). However, major alien predators continue devastate native species. A recent report on alien Lake Trout in Yellowstone Lake found that native cutthroat trout decreased to their lowest levels in recorded history. A recent study of Burmese Pythons in Everglades National Park, found the apex predator coincident with decreases in raccoons (99.3%), opossums (8.9%), bobcats (87.5%), and the absence of rabbits in recent road surveys in the Park. In Hawaiian national parks, ground nesting birds continue to be decimated by introduced mammals. Alien fishes continue to consume native fish, invertebrates, and amphibians; and spread alien pathogens including water mold and whirling disease.  Another report showed that more than 450 alien forest insects are established in the United States forests, including national parks. Forest composition in most eastern parks has been radically altered by harmful alien forest pests. The increasing threat of zoonotic diseases related to human health (e.g., plague, West Nile Virus, Asian bird flu) may pose a significant challenge to providing for the public enjoyment of the national parks. Combined, results suggest it is time to revise science and management strategies to preserve park resources for future generations.