In early 2016, Giovanni Melcarne, an agronomist and the owner of an extra virgin olive oil farm in Gagliano del Capo, walked through the southern Italian countryside of Puglia. He was with a fellow olive-oil farmer who had called and told him there was something he had to see.

The two approached a centuries-old olive tree growing at the edge of the street along a traditional stone wall. All around, the old olive trees that covered the red clay were either dead or in an advanced state of decay, filling the landscape with an unnatural greyness. Melcarne was not surprised: At least 2 million olive trees in Puglia looked this way, including many of his own.