After more than a decade of explosive growth, sales of local food at U.S. farmers' markets are slowing. A January report from the U.S. Department of Agriculture shows that while more farmers are selling directly to consumers, local food sales at farmers markets, farm stands and through community supported agriculture have lost some momentum.

From 2007 to 2012 the value of food sales of farmers face-to-face with consumers dropped by 1% in real dollars. For some context, from 2002 to 2007 that value increased 32%. The increase was 36% in the five-year period before that.

Even the rate of growth in the number of farmers markets nationwide has slowed in recent years after several years of rapid growth, rising just 1.5% from 2013 to 2014.

That's not necessarily bad news for farmers. In fact, it could mean the entire local food movement is growing up.

So what explains the slowdown? Here are some of the theories.

We've Hit Peak Farmers Market

There could be some stagnation in the number of new people buying local food. Or as the USDA puts it, "a plateau in consumer demand for local food."

Rising demand in the last several years has lead to the opening of many new markets. There were 8,268 farmers' markets operating in 2014, up 180% since 2006.

"In densely populated urban areas, farmers' markets often compete with each other for vendors and consumers," the report reads. "In other areas, newer, more strategically located farmers' markets may lead to the decline…