Build a 21st century farming system that is both sustainable and capable of feeding a projected 9.5 billion people by mid-century: Is it possible to do both?

For now, many agricultural experts throughout the world are certain of one thing: Two of the resources on which farming has depended in the past to feed the world — water and fossil-based energy — will be in perilously short supply by mid-century.

Add to this the challenge of spiking food prices, which have followed as people in the developing world improve the quality of their diets.

Speaking at the Oxford Farming Conference earlier this year, Professor John Beddington, chief science adviser to the British government, says global agriculture will have to produce 50 percent more food by 2030 to feed the growing population.

These factors present researchers and policy makers with a daunting, if not contradictory, challenge: Develop a new farming model that is both sustainable — capable of functioning over the long term with only a fraction of the resources available to it — and also efficient and cost-effective enough to feed billions more by mid-century.

Stressing the need for Britain to grow more of its food while reducing the emission of greenhouse gases, Hilary Benn, the United Kingdom's secretary of state for the environment, outlined earlier this year the first new British agricultural policy in decades, one that possibly may offer insight into the kind of farming model that eventually may emerge.

"We need to produce more food. We need to do it sustainably. And we need to make sure what we eat safeguards our health," he said in announcing the policy.

Benn said British consumers have a role to play by demanding greener food from retailers, by wasting less, and, equally significant, by growing more of their own food.

Likewise, Benn hopes the increased consumer demand for greener food will encourage food businesses, supermarkets and manufacturers to offer more locally produced, healthier food that creates a smaller environmental footprint.

Benn also called for the development of more "meanwhile" leases for landowners and voluntary groups, who could use these temporary allotments to expand homegrown fruit and vegetable production.

Benn and other British policymakers believe this strategy would enhance community spirit as well as physical and community health.

But this begs the original question: Is a farming policy that emphasizes more sustainable practices, particularly homegrown and locally marketed food, any better equipped than the current model to feed the world?

No, say many experts.

At Auburn University, Paul Mask, the Alabama Cooperative Extension System's assistant director for farm programs, says there are many compelling reasons for researchers and policymakers to push for more sustainable farming practices.

Even so, the current farming model is prized not only for its efficiency, but also for its cheapness. The spike in prices that inevitably will follow the widespread adoption of many sustainable practices is more than many consumers, especially those on the lower end of the economic spectrum, will be willing to bear.

"What it (the current farming model) has meant is that people in our country and, to an extent, in other developed countries, are afforded cheap food," says Mask, who nonetheless expresses pride in growing a substantial share of his own food.

"Even raising the price of, say, chicken by just 10 cents a pound to make it a more sustainable product would have adverse effects on tens of millions of people."

Another Extension professional who expresses reluctant agreement with this view is Home Grounds Coordinator Kerry Smith, who oversees horticulture-related educational programming throughout Alabama.

Even so, Smith foresees a major social change stemming from the renewed interest in homegrown produce and even meat — foods that occupied a prominent place on the kitchen tables of earlier generations.

"Younger people, especially those in their teens and twenties, are giving a lot more thought to the day-to-day stuff, such as their food, their clothes and, among young women, even what they put on their faces," Smith observes.

"While we can't feed the entire nation with backyard gardens, these certainly will play a significant role in helping us build this sustainable farm model."

The ensuing debate over British agricultural policy reflects the ongoing struggle to balance sustainability with large-scale farming. In addition to calling for expanding homegrown food production and local farm markets, many leading British researchers and policymakers also concede that cutting-edge science will have an even more prominent role to play.

For his part, Beddington says that feeding the emerging world population will require production of more crops on less land and greater use of emerging technologies, especially the genetic modification of food and nanotechnology.