Yale economist Robert Shiller has a reputation for being one of the most astute “bubble-spotters” in the world, having warned of both the tech stock bubble of the late 1990s and the recent U.S. housing bubble shortly before they popped.

Now, he says a couple areas are on his bubble-radar: farmland, and commodities. “My favorite dark-horse bubble candidate for the next decade or so is farmland,” Shiller writes on the web site Project Syndicate. He says the current farmland story has the “new era”, everything-is-different-now tone that often dominates investor thinking when bubbles are forming. “Farmland, at least in certain places, seems to have the most contagious ‘new era’ story right now,” he writes. “It was recently booming, up 74% in real terms in the US in the decade ending with its price peak, in 2008. And the highly contagious global-warming story paints a scenario of food shortages and shifts in land values in different parts of the world, which might boost investor interest further.”

Another related area that Shiller is keeping an eye on: commodities, with food and fuel prices skyrocketing amid concerns about weather, global warming, and the Middle East.

Shiller does not, however, see a bubble in stocks.

He says the huge surge in stocks since March 2009 “doesn’t look like a bubble, but more like the end of a depression scare. The rise in equity prices has not come with a contagious ‘new era’ story, but rather a ‘sigh of relief’ story.” And, he says, he’s not seeing housing bubbles forming right now, even in areas where prices have risen substantially in the past year or two.