American farmers have been complaining of labor shortages for several years now. Given a multi-year decline in illegal immigration, and a similarly sustained pickup in the U. S. job market, the complaints are unlikely to stop without an overhaul of immigration rules for farm workers.

Perhaps half of U. S. farm laborers are undocumented immigrants. As fewer such workers enter the U. S., the characteristics of the agricultural workforce are changing. Today's farm laborers, while still predominantly born in Mexico, are more likely to be settled, rather than migrating, and more likely to be married than single. They are also aging. At the start of this century, about one-third of crop workers were over the age of 35. Now, more than half are. And crop picking is hard on older bodies. One oft-debated cure for this labor shortage remains as implausible as it has been all along: Native U. S. workers won't be returning to the farm.

Efforts to create a more straightforward agricultural-workers visa that would enable foreign workers to stay longer in the U. S. and change jobs within the industry have so far failed in Congress. If this doesn't change, American businesses, communities and consumers will be the losers.

Mechanization is not the answer either -- not yet at least. Production of corn, cotton, rice, soybeans and wheat have been largely mechanized, but many high-value, labor-intensive crops, such as strawberries, need labor. Even dairy farms, where robots currently do only a small share of milking, have a long way to go before they are automated.

The H-2A visa has no numerical cap, unlike the H-2B visa for nonagricultural work, which is limited to 66,000 annually. Even so, employers frequently complain that they aren't allotted all the workers they need. The process is cumbersome, expensive and unreliable. One survey found that bureaucratic delays led H-2A workers to arrive on the job an average of 22 days late. And the shortage is compounded by federal immigration raids, which remove some workers and drive others underground.

As a result, farms have grown increasingly reliant on temporary guest workers using the H-2A visa to fill the gaps in the agricultural workforce. Starting around 2012, requests for the visas rose sharply; from 2011 to 2016 the number of visas issued more than doubled.

In a 2012 survey,71 percent of tree-fruit growers and nearly 80 percent of raisin and berry growers said they were short of labor. Some western growers have responded by moving operations to Mexico. From 1998-2000, 14.5 percent of the fruit Americans consumed was imported. Little more than a decade later, the share of imported fruit had increased to 25.8 percent.

In effect, the U. S. can import food or it can import the workers who pick it.