By Tamar Haspel

Special to The Washington Post

The food movement has a problem: It's right about what's wrong with our system, but wrong about how to fix it.

But what is the "food movement?" I hear you asking. For these purposes, we'll call it the loose coalition of sustainability-minded people calling for the food system to be more focused on environmental and human health. There are lots of players with lots of agendas, but the key issues boil down to a familiar few: We have a chemical-intensive system that crowds out biodiversity, depletes the soil and pollutes the water to grow corn and soy for cheap meat and processed food, which make us fat and sick. While we can talk about the extent to which these things are true, it's hard to look at the dead zone in the Gulf of Mexico or the inexorable rise in obesity and deny that they're problems.

How do we fix it? You've seen the bumper stickers. Buy fresh, buy local. Support the small, diverse, organic (or organic-ish) farm that supplies the farmers market and local restaurants with fresh vegetables. And that's a great idea; local agriculture brings a host of benefits, including delicious strawberries and a much-needed reminder that food has to come from somewhere.

But it cannot fix that chemical-intensive system that crowds out biodiversity, depletes the soil, pollutes the water, etc. And that's not a lack of confidence in, or enthusiasm for, that kind of small farm. It's simply a recognition that there are economic, logistic, topographical and even arithmetic reasons that those farms can only be a small slice of a reimagined, responsible, food system.

Here is one reason: They don't grow the right stuff.

The crops these farms grow are fruits and vegetables, and, even if we all eat a produce-rich diet, fruits and vegetables cannot be more than a sliver of our agricultural system. The United States has about 400 million acres of cropland, and only about 4 percent of it is fruits and vegetables (what the USDA calls "specialty crops"). I know I'm repeating myself here, but if we all ate the recommended servings of produce, we might double that acreage. However, there is no realistic scenario under which produce is more than 10 percent of cropland. And 10 percent cannot be the solution.

And they can't grow the right stuff. The reason small, local, diverse farms grow vegetables (and sometimes livestock) is that those are high-margin products. The crops that carpet the vast swaths of the Midwest cannot be successfully grown small and local, because you need economies of scale to make those crops profitable. What's great about staple crops such as oats, lentils, barley and, yes, corn and soy is that they produce huge amounts of nutritious, affordable food per acre.

Even though the lion's share of agriculture's impact on human and environmental health comes from the industrialized portion of our food supply, the fix isn't to replace industrialized with nonindustrialized, or corn with broccoli. The fix is to focus on the grains and legumes that are staple crops; grow them better and incorporate them, whole, into our diet.

I talk to a lot of farmers of commodity crops who are making environmental impact a top priority and implementing practices to improve their soil health, reduce nutrient runoff and retain water. We have to start thinking about how consumers can use their buying power to support those farmers. It's a tall order, in part because it means involving the large companies that both supply and buy from those farmers, and many of those companies have been tagged as the enemies of environmental and public health. But the first step has to be the acknowledgment — say it out loud! — that local and organic can't solve the problem.

The food movement has been instrumental in educating consumers about the problems in our system. It's time to focus on fixing them.

— Tamar Haspel writes about food and science and farms oysters on Cape Cod, Massachusetts.