Up to A$15b would be spent on environment protection，which the prime minister noted "says a lot about where the threats are coming from".
【翻译】高达150亿澳元将用于环境保护，总理指出，这“充分说明了威胁来自何处”。

这是一个“嵌入式定语从句”。其中，the prime minister noted 为“嵌入式”主句，which  "says a lot about where the threats are coming from" 为其宾语从句。
which 作从句主语，指代前文整个主句内容。

say a lot about...充分说明。