Invasive Species

Non-indigenous, invasive species are a serious threat to wildlife and habitats at Wallkill River Refuge. Exotic plants degrade habitat by converting diverse native plant communities into single-species monocultures, and introduced animals compete directly with native wildlife. In fact, invasive species are one of the most important threats to the National Wildlife Refuge System as a whole.

All refuge habitats and wildlife species are vulnerable to the effects of invasive species. Purple loosestrife and Phragmites have taken over many Refuge wetlands. Consequently, habitat for the federally-threatened bog turtle, migrating waterfowl, and a wide diversity of other wetland dependant wildlife has been degraded. Refuge grasslands are being invaded by Canada thistle and spotted knapweed (Centaurea stoebe). Shrublands are becoming dominated by multiflora rose, common buckthorn (Rhamnus cathartica), and autumn olive (Elaeagnus umbellata). Refuge forests have become invaded by tree-of-heaven (Ailanthus altissima), Japanese barberry, and garlic mustard. The introduced mute swan (Cygnus olor) competes with native waterfowl and marshbirds for food resources and nesting areas, and the feeding activities of these large birds damage wetland ecosystems. Feeding and spawning common carp (Cyprinus carpio) kill aquatic plants and increase water turbidity, and as a result, Refuge waters provide poorer habitat for native fish. Feral cats kill countless small mammals, ground-nesting birds, and songbirds. Other important invasive species on the Refuge include Japanese honeysuckle (Lonicera japonica), European bush-honeysuckles (L. tatarica, L. morrowii), Asiatic bittersweet (Celastrus obiculatus), Norway maple (Acer platanoides), Japanese knotweed (Polygonum cuspidatum), and gypsy moth (Porthetria dispar).

The refuge is currently participating in a Regional Invasive Plant Species inventory and Mapping Initiative. The purpose is to conduct a basic invasive plant inventory of refuge lands which will locate, identify, and map invasive plant species. This information will be used to guide development of control, monitoring, and evaluation initiatives.