1970: Neil Young, After the Gold Rush

The beginning of a general sense of pessimism about the future coming from young Boomers, manifesting in reemergence of a concern for the environment: "Look at mother nature on the run in the 1970s."

Here is an interesting graph of the frequency of the phrase mother nature, hitting a peak in the 1920s, then falling precipitously until the mid-1960s, when it rises again.