The shortage of farm workers this year may lead to fewer sustainable products.
The agriculture department responded to the shortage of migrant farm workers by suggesting that the farmers mechanize their harvesting. This could create an undo burden on organic, and sustainable growing.
Imagine a farmer who has nourished and cared for a tomato crop through a whole season. They are now ripe and ready to pick. The machines are designed to pick the tomatoes green, if you use it on ripe tomatoes they will be crushed. Now he/she is unable to get enough workers to pick them. Any loss is a critical loss, but coming at the end of a growing season the loss is at its highest cost, and now some of the tomatoes will rot on the vine due to an insufficient numbers of workers.
Machines also need clear paths to harvest fruits or vegetables. This means the field must be set up for the machine, not for the plant. It also means the crop must grow straight. Biodiversity in the field becomes difficult and plants must be genetically manipulated by either by cross pollination, or gene splicing. Corn has long been genetically engineered with this in mind. A plants attempt to maximize surface area, therefor photosynthesis, by reaching for the sun and spreading out to where there is open land. Most specialty produce can not be engineered to fit tis mold. Squash and melons will never achieve straightness.
Since many specialty crops can't be harvested by machines, the burden of fewer of migrant workers falls on small, local sustainable farms. Large corporate farms, which produce mainstream crops will prosper, while small local diversified farmers will suffer the most.
One of the many stories of this can be found on marketplace (though they don't speak specifically to the sustainable issues).
http://marketplace.publicradio.org/shows/2006/02/17/PM200602178.html