Barrier islands are long, narrow strips of land that run parallel to the coastline. They are formed by the action of waves and currents, which deposit sand and sediment over time. These islands play a crucial role in protecting the mainland from storms and high waves, acting as a buffer that absorbs the impact of ocean forces. Many barrier islands are home to unique ecosystems, including sandy beaches, marshes, and dunes. They provide habitats for various wildlife, such as sea turtles and shorebirds. Popular examples of barrier islands include the Outer Banks in North Carolina and Fire Island in New York.