Yeast occurs in the environment but, contrary to popular belief, not necessarily in vineyards. Scientific research has shown that microorganisms are carried by wind, humans, birds, and especially insects (wasps, bees and flies). Since no birds or insects are specific to a single plot of land or terroir, the idea that each yeast is land- or terroir-specific is not established even though recent researches showed a recurrence of few strains among hundreds identified on a same location. As a matter of fact, the yeasts strains responsible of the spontaneous fermentation (less than a dozen) are unpredictable.
Yeast populations contain a wide range of strains, which are constantly migrating. For example, some yeast found in the Kemeu River vineyard in New Zealand are the same as European yeasts in… French oak barrels! Thanks to new genetic analysis tools, all yeast strains can now be accurately identified.