Why is the tideland so sensitive?

The tideland is the flat coastal area, which is under water twice in a day and dries out in between. More than 3000 species of plants and animals such as shells, sand worms, crabs, prawns, fish, and sea birds live in this small area. Such coastal areas rich in diverse species have developed only at abut hundred coasts all around the world. The largest tideland is at the coast of the North Sea, and the second largest is at the western coast of South Korea. The equilibrium among the species is easily disturbed by outside influences such as water pollution or a slight rise in the sea level. Any such disturbance endangers the entire tideland.