Coastal sand dunes are created and shaped by wind and tide. Sands deposited by rivers and offshore currents build them into physical barriers that protect the coastline and inland areas from saltwater intrusion and erosion while also absorbing wave energy in ways that keep the soft beach from eroding away. Dunes protect coastal population from flooding during coastal storms and act as homes and shelters for a variety of plants, animals, nesting sea turtles, and shorebirds. Beaches, barrier islands, and coastal sand dunes are dynamic, changing natural systems. Like geology with the fast-forward button always on, they change with weather, tides and storms.