In their greed for wine, and to collect every possible penny from the exertions of the soil and sunshine (not to mention unimaginable amounts of human labor), people have planted, over the last 150 years, millions of acres of vineyards in this several-county region. Eventually, all will succumb to some insect, some disease, some depletion...or perhaps come to be replaced with food crops if they're lucky enough not to be covered with houses.
Half these rows are gone now; the land has had a cover-crop of radishes grown and disced into the soil, and now waits to be planted with the currently-popular Cabernet. When people have had their fill of that and stop buying it, some other variety will come along to take its place.