Salt marshes are among the most productive habitats in the world and provide important benefits by protecting the mainland from flooding and erosion, filtering sediments and some pollutants from the water, and serving as a safe nursery for many species of coastal fish and shellfish. Nearly half of New Jersey's 245,000 acres of salt marsh lies along the Delaware Bay and the Atlantic coast of Cape May and Atlantic Counties. Though they may seem to be only waving acres of grass, salt marshes are a critical link in the coastal food chain, supplying vital nutrients for crabs and other crustaceans, for nearly all of New Jersey's coastal fish, and for huge flocks of shorebirds during their spring and fall migrations.