 The National Park Service (NPS) is concerned about the impact of Bankers on the environmental health of North Carolina's barrier islands. Initially, the NPS believed that the non-native Bankers would completely consume the Spartina alterniflora grasses and the maritime forests, as both were thought to be essential to their survival. Research in 1987 provided information on the horses' diet that suggested otherwise. Half of their diet consisted of Spartina, while only 4 % of their nutrients came from the maritime forest. The study concluded that sufficient nutrients were replenished with each ocean tide to prevent a decline in vegetative growth from overgrazing. A 2004 study declared that the greatest impact on plant life was not from grazing but from the damage plants sustained when trampled by the horses' hooves. Bankers pose a threat to ground-nesting animals such as sea turtles and shorebirds. Feral horses interrupt nesting activities and can crush the young.
