VOA慢速英语 美国发现两种最古老的珊瑚新品种

　　Much of the information came from observations made by thousands of volunteers in more than four thousand places over forty years. The United States Fish and Wildlife Service led the effort to combine the information into one report.

　　VOICE TWO:

　　Interior Secretary Ken Salazar praised the report as an important scientific document on the health of American birds. But it is not only a warning about falling bird populations. The health of bird species tells researchers a lot about the condition of the environment.

　　The study grouped birds by the environments in which they live. It said grassland bird populations fell by about forty percent in forty years. That was the biggest drop reported. One reason for this is the disappearance of grasslands in the central United States. The report says only two percent of the grasslands that existed two centuries ago remain today.

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　　VOICE ONE:

　　Birds depend on their environment to provide food and shelter. The report said loss of habitat is the biggest threat to American birds. Sixty-seven species are federally listed as endangered or threatened. But the report lists one hundred eight-four species that are considered in danger because of limited habitat, serious threats or falling populations.

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