Forward to the past; removal of non-native animals from Channel Islands National Park

Channel Islands National Park consists of five islands off the coast of southern California.  The islands were never connected to the mainland and provide habitat for many plant and animal taxa that occur nowhere else.  Additionally, the islands provide critical habitat for biota which depend on the naturally lower levels of predation, herbivory, and disturbance typical of islands.  Since the 1970s, the National Park Service and our partners have eliminated most of the non-native mammals introduced to these islands.  Three of the park islands, Santa Barbara, Anacapa, and Santa Cruz, are free of non-native mammals.  Deer and elk remain on Santa Rosa Island and black rats remain on San Miguel Island. There has been substantial ecological recovery as a result of the non-native animal removals.  The population of Xantus’s murrelet, a rare nocturnal seabird, is slowly increasing on Anacapa Island as a result of eradicating black rats.  The western harvest mouse has increased in numbers and extent on Santa Cruz Island, likely in response to increases in vegetation due to removal of sheep.  Native plants are increasing on Santa Rosa Island in response to removal of cattle.  However, some areas, such as highly eroded habitats, have been very slow to change.  The spread of some non-native plants has been facilitated by the presence of non-native animals and, therefore, removal of the animals has been an effective management tool.  However, some invasive plants require additional control actions.  It is important to monitor the ecological effects of animal eradications and determine what additional management may be necessary to avoid unintended negative consequences.  Interventions will be needed for many years to protect and recover the natural biological diversity of the Channel Islands.