在过去的两个世纪中 ,象天然湿地这样适合于动植物生长的环境已大大减少。 18世纪 80年代 ,在全美范围内有一半以上的湿地已被排干、平整、淹没或填充。密西西比 59%的原始湿地已不复存在 ,其中 54%已被转变为农业耕地。随着东南地区农业生产的不断扩大 ,人们为了增加耕地面积 In the past two centuries, the environment suitable for the growth of animals and plants like natural wetlands has been greatly reduced. In the 1880s, more than half of wetlands across the United States had been drained, smoothed, submerged or filled. 59% of Mississippi’s virgin wetlands no longer exist, of which 54% have been converted to agricultural land. With the continuous expansion of agricultural production in the southeast region, people are trying to increase their cultivated area