19. Dr. Myers and Dr. Worm argue that their work gives a correct baseline, which future management efforts must take into account.

【分析】多重復合句。句子主干為Dr. Myers and Dr. Worm argue that, that引導賓語從句。賓語從句中又含有which引導的定語從句修飾先行詞baseline。定語從句中 which 作take的賓語,構成 take sth. into account。
【譯文】邁爾斯博士和沃爾姆傅士指出他們的工作給出了一個正確的基線,未來的管理工作必須對此加以考慮。
【點撥】take sth. into account“考慮到…”。此外，相同意義的表達還有 take sth. into consideration;allowing for sth. ; in view of sth. ; have sth. in mind 等。

20. The notion is that people have failed to detect the massive changes which have happened in the ocean because they have been looking back only a relatively short time into the past.

【分析】多重復合句。本句中含有三個從句。首先, that引導的表語從句；其次是which引導的定語從句，修飾先行詞changes;最后是由because引導的原因狀語從句。
【譯文】這個想法認為人們無法測定海洋中的大規模變化，因為他們僅僅考慮了一段相對較近的歷史。