Thousands of species of fish, shore birds, marine mammals, clams, shellfish and other wildlife survive in and around estuarine habitats. Many fish and shellfish species, including most commercially and recreationally important species, depend on the sheltered waters of estuaries as home to spawn and for their offspring to grow and live. Due to the high productivity of living organisms, migratory birds also take estuaries as ideal places for resting and reproducing. In addition to serving as important habitats for wildlife, estuaries also provide valuable environmental services. The water flowing to the ocean carries sediments, organic and inorganic nutrients, and pollutants. Much of the sediments and pollutants are filtered out when they flow through wetlands, swamps and salt marshes. This filtration process deposits harmful pollutants and then creates an environment for microbial biodegradation of these sediments. Estuarine plants also can absorb tide and storm surges, providing peaceful and stable habitats for widelife. This natural buffer helps to prevent erosion and stabilize the coast. The transition character of estuaries provides important research value for scientists. A wide range of problems in biology, geology, chemistry, physics, and sociology are studied in and around estuaries. Estuaries also provide a great deal of aesthetic enjoyment for the people who live, work, or recreate in and around them.