Typically old-field communities are dominated by nonnative pasture or soil cover grasses, however over time, in the absence of disturbance and active farming, they begin to function as natural systems, replacing the ecological void of critical grassland and estuarine habitat lost to urban development and industrial farming. Old-fields are the preferred habitat of a range of species. Some like Townsend's Vole, are keystone food-chain species, providing a critical food source for grassland dependent raptors like Barn Owl, Short-eared Owl and Northern Harrier. Other species like the fannini or coastal subspecies of Great Blue Heron, depends on habitats like old-field and Townsend's Vole for foraging, especially critical for juveniles in the winter. Major old-field communities on the South Coast are found in the Fraser Lowlands from from Richmond to Chilliwack including Terra Nova in the Fraser Estuary, Boundary Bay in Delta, Campbell Heights, Crescent Beach, Tynehead Regional Park, Campbell Valley Regional Park in Surrey/Langley, the Lower Pitt River running through Maple Ridge, Pitt Meadows and Coquitlam and Barnston Island in the Fraser River. Some of the most significant old-field areas remaining on the on the South Coast are Colony Farm Regional Park in Coquitlam/Port Coquitlam and the Hatzic Prairie area near Mission.