Paul Mask was reminded of one of the basic realities of modern farming recently while visiting an ailing aunt at a hospital.

Stopping for lunch at the hospital cafeteria, Mask, who holds a doctorate in agronomy and soils and serves as the Alabama Cooperative Extensions System's assistant director for agricultural programs, overheard a handful of hospital workers bemoaning the recent spike in food prices.

"One of them was talking about how she had placed a chicken in her cart, only to return it and look for another alternative when she realized how much more expensive it was," Mask says.

Her experience reminded Mask of one of the basic realities of modern farming.

"Here in the United States, we spend a smaller proportion of our disposable income on food than anywhere else in the world." he says.

"Our system has been geared to make food as cheaply as possible," Mask says.

And when occasional supply-and-demand factors interfere with these prices, people notice them, he says.

Mask hails modern farming as one of history's greatest scientific achievements, though one that has been heavily dependent on two resources that are projected to be in perilously short supply in the future.

"Our current system is based on cheap energy and abundant water," Mask says. "As long as we have these two things, it works, but I don't think we can expect this will stay the same forever."

For Mask, this raises a disturbing question: Is modern farming sustainable over the long haul? Can the system that has provided much of the world with cheap, abundant food continue to keep pace with a rapidly expanding global population with less water and energy?

Critics of the current farming system advocate an alternative: A system that incorporates elements of pre-modern farming, which incorporated sustainable practices as well as homegrown food production and local farm markets.

Kerry Smith, coordinator of Alabama Extension's Home Grounds team co-leader, has seen this view take hold among a growing number of people.

"There are a lot of things fitting together," Smith says. "People are having conversations about home-grown food, they're getting passionate about it, and they're starting programs."

This newfound passion, she believes, stems from a genuine desire among people to know where their food comes from.

It's also contributed to the growth of a relatively new approach to homegrown farming, known as community-supported agriculture (CSA). Under this approach, customers contract with growers to produce a certain volume of food — a system that provides buyers with a steady supply of food and growers with a degree of certainty in what is otherwise considered a volatile line of work.

Smith also notes the rapid growth of the organic food movement — something she never expected would gain widespread acceptance because of its high price.

"When we first started seeing organic vegetables at the grocery store, my first reaction was 'piddle.'" She recalls. "It cost too much and I believed Americans were so supermarket oriented they would never pay for such costly produce.

"But that sector keeps growing and growing."

Can such a model, which is arguably more sustainable, at least on a small scale, actually replace the current system?

Smith believes that some hybridized farm model could emerge that incorporates some elements of small-scale food production.

Other experts, including Jim Novak, an Extension economist and Auburn University professor of agricultural economics, believe that whatever emerges will closely resemble what is in place now.

"Here's the problem: The population is increasing," Novak says. "We can produce and buy locally, but I don't see this as solving our problems on a vast scale unless we have a massive back to the land movement.

"And it's a fact that some of our best agricultural land located near urban areas is under asphalt."

Mask agrees. Whatever emerges over the next few years will retain many, if not all, of the elements of the current system, he says.

"Growing populations will demand the same measure of efficiency associated with the current system — and this means continuing to grow food on a large scale."

Mask says the nation's land-grant universities are already focusing on ways to incorporate sustainable practices into food production, developing new sources of renewable energy and new plant varieties equipped to survive with less moisture.

For his part, Mask played a major role in securing a technology that could go a long way toward enhancing sustainable farming practices: Precision farming, which uses GPS technology to reduce fuel and water use as well as the levels of farm chemicals that ultimately leach into surrounding surface water.

While conceding the daunting challenges that lie ahead, Mask believes a new sustainable farming model capable of feeding some 9 billion people is achievable, citing crop breeding successes as a prime example how science has overcome such challenges in the past.

"Just look at corn grown in my grandfather's time," Mask says. "When he was a young farmer, he typically could expect about a 20-bushel per acre yield. Today, some growers get as much as 200 bushels.

"I talk with breeders all the time, and I know there is a lot more yield potential left in the crops we've already developed."