U.S. agriculture faces many challenges. The short list includes pests, crop and animal disease, high input costs, poor commodity prices, trade issues, uncooperative weather, ill-conceived regulations and the disconnect with urban America.

But there's another threat, a long-term one, that American agriculture can't afford to ignore: the irrevocable loss of our limited supply of ag land. A new report from the American Farmland Trust - examined in this Agweek article - reveals how serious the danger is.

• Roughly 31 million acres of ag land nationwide were lost to development from 1992 to 2012. That's equivalent to nearly all the farmland in Iowa or the entire land mass of New York State. It's also double the amount of lost land previously documented.

• Of those 31 million acres, 11 million acres were the "best" farmland, or the land best suited for intensive cultivation with the fewest environmental impacts.

• Expanding urban areas accounted for 59 percent of the lost land, with houses built on 1- to 20-acre plots responsible for the other 41 percent.

Those numbers are disturbing, or should be. Just about everyone in U.S. agriculture knew there was a problem; hardly anyone realized it's that bad. The reality is, houses, roads, strip malls, golf courses and more - nibble by nibble, acre by acre - eat up farmland.

Yes, the rising per-acre productivity of U.S. agriculture partially offsets the loss. But losing 31 million acres - or 3 percent of all farmland used by farmers and ranchers in the continental United States - is a tremendous handicap. The loss of even more farmland would worsen that.

Not us vs. them

Agriculturalists need to avoid framing this as an us-vs.-them issue. Urban residents understandably want more places to live, work, drive, shop and recreate; trying to deny them would be neither wise nor realistic. And remember, some of the urban residents are the friends or relatives of farmers and ranchers; some are even retired farmers and ranchers themselves.

So what's the answer?

That's the question Agweek asked Mary Podoll, North Dakota state conservationist, who contributed to the report. She served on an advisory committee for it while she was deputy chief for soil survey and resource assessment at the Natural Resources Conservation Service, an arm of the U.S. Department of Agriculture.

Her answer: "We need to be smarter (about development), and data collection is the key."

We agree. Sound data can help our nation, states and individual communities be smarter about development, limiting the amount of prime farmland that's lost.

Let's be honest. Farmers and ranchers contribute to the problem, albeit in a small way. Yes, more and bigger bins, barns and other buildings can increase efficiency - we understand why they're built - but the new structures often take bits and pieces of ag land out of production.

As we tell urban Americans to be smart about development, we'd better be smart, too. If we aren't, we undermine our credibility.

The American Farmland Trust has a number of recommendations on how to tackle the problem. One example: Enact federal tax code changes that encourage keeping ag land in production and transferring it from one generation of farmers and ranchers to the next.

The full report with the entire list of recommendations is available here.

U.S. agriculturalists, faced with so many challenges, may be tempted to throw up their hands in frustration and do nothing about lost farmland. Resist the temptation; nothing is more important than protecting our farmland.

The task ahead won't be easily or quickly achieved. But we need to work at it. And we need to succeed.