1. Wave action: Waves are the primary cause of beach erosion. As waves break on the shore, they carry away sand and other sediments, which can lead to the gradual erosion of the beach.

2. Tides: Tides can also contribute to beach erosion. High tides can bring in more water and waves, which can increase the amount of erosion that occurs. Low tides can expose more of the beach to the wind, which can also lead to erosion.

3. Storms: Storms can cause significant beach erosion in a short period of time. High winds and large waves associated with storms can quickly carry away large amounts of sand and other sediments, resulting in severe beach erosion.

4. Sea level rise: Sea level rise is another major factor contributing to beach erosion. As the sea level rises, it can inundate beaches and erode the shoreline. Sea level rise can also lead to increased wave energy and storm surge, which can further accelerate beach erosion.

5. Human activities: Human activities can also contribute to beach erosion. Construction of coastal structures, such as jetties and groins, can alter the natural flow of water and sediment, leading to beach erosion. Beach replenishment, the process of adding sand to a beach to combat erosion, can also have unintended consequences, such as altering the natural beach profile and ecosystem.