人教高中英语高二下UNIT13-2（在线收听）

                                                                                           NATURE'S NURSERY: ESTUARIES
         As the oceans are the source of life on earth, the estuaries are our planet's nurseries. An estuary is the body of water where a river meets the ocean. Salt water from the ocean and fresh water from the river mix together in an estuary. This mixing of fresh and salt water creates a unique environment filled with life of all kinds -- a zone between the land and the sea. Estuaries are the homes of thousands of animals and plants. Many cities and towns are built near estuaries, and a lot offish are caught in estuaries.
        Estuaries are great places for nature's young ones. Here, animals can enjoy all the benefits of the oceans without having to face many of the dangers. Tides provide energy for the ecosystems, but estuaries are protected from waves and storms by islands, mud or sand. Nutrients arrive in estuaries from both the land and the ocean. The density of living creatures is higher than in any other habitat on earth. The diversity of life in estuaries is incredible -- birds, fish, marine mammals, shellfish and other species all come here to live, feed and reproduce.
       Estuaries are also important because they absorb nutrients and pollutants from water coming from inland sources, thus cleaning our water. Unfortunately, this function also makes estuaries very sensitive to environmental pollution. Since estuaries protect animals and plants from storms and floods and prevent erosion, protecting estuaries is very important.
       Finally, estuaries provide both recreation and education for human beings. Most of us enjoy fishing, swimming and having fun on the beach, and scientists and students have endless opportunities to study a variety of life in the habitat. Estuaries also contribute to the economy through tourism and fishing.