With such a huge decrease in population, European medieval society as a whole was seriously affected.

随着人口的急剧减少，整个欧洲中世纪社会受到了严重的影响。

Secondly, the reading states that aside from sea otters, other small sea animals also decreased in population due to pollution.

第二，文章指出除了海獭以外，其它海洋动物的数量也因污染而减少。

It says that the eastern gorilla, which is found in the African nations of Democratic Republic of Congo, Rwanda and Uganda, has decreased in population by more than 70 percent in the last 20 years.

报告称，在刚果民主共和国、卢旺达和乌干达等非洲国家发现的东部大猩猩在过去 20 年中数量减少了 70% 以上。