Marine biologist Daniel Pauly discovered that fishermen working the eastern seaboard of North America were oblivious to the fact that their catches had declined 97 percent since written records were kept. Each generation of fishermen had reset their baseline to whatever they were catching at the beginning of their career.
Pauly wrote up these findings in his 1995 paper "Anecdotes and the shifting baseline syndrome of fisheries".
This is very much the signficance of David Fleming's quote: "History forms our expectations; it is our data. Without a sense of history, our expectations are the product of how we live now."
This is also why Hope Jahren wrote [[The Story of More]].