VOA慢速英语 美国发现两种最古老的珊瑚新品种

　　The report also notes successes in bird conservation efforts. For example, the numbers of many wetland birds have recovered since measures were taken to protect more than twelve million hectares of wetlands.

　　One hundred thirty-nine wetland species have increased in number since the late nineteen-seventies. Pelicans, herons and geese are just a few of many recovering wetland species.

　　VOICE TWO:

　　Numbers of America's national bird, the bald eagle, have recovered largely because of measures to fight pollution. In nineteen seventy-two, the federal government banned most uses of the insecticide D.D.T. The chemical used to kill mosquitoes also caused bird egg shells to thin and break. Species like the bald eagle, peregrine falcon and osprey nearly disappeared. Now, their populations seem secure.

　　But threats to other species continue to grow. Land development and agriculture are just two uses of natural resources that change and destroy environments that birds need. The cutting of forests is threatening woodland species like the Northern Spotted Owl.