From the agricultural capital of the world, yes, the decline is varieties is quite serious, as the possibility of a pestilence attacking those few remaining becomes quite serious, as it could decimate production of staple food items. (Although not a food crop, Dutch Elm Disease has decimated the elm trees of all America, for example.) There is a citrus problem right now in Southern California -- one of the orchards was put in quarantine from the same problem which in the last few years has been attacking the Florida trees. While diversity may not always be a good thing, in agriculture it certainly is, as new problems continually erupt. An additional, and quite political, issue is the production of hybridized, patented seeds owned by the big corporations which then attack the farmers who try to preserve their own seeds for planting the next year's crop, the way farmers for thousands of years have done. Or the genetically altered seeds which depend on expensive chemical applications from corporate sources to grow (eg. Roundup resistant produce).