We've been talking about the decline of coral reefs in tropical areas all over the world—how natural and man-made stresses are causing them to degrade or in some cases, to die.

我们之前提到了世界各地热带地区中珊瑚礁的衰落，即自然和人为（造成的）压力是怎样造成珊瑚礁退化，或者甚至在某些情况下，造成它们死亡的。