Scientists have discovered whole new categories of fungi living in an unexpected place, the chilled soil beneath mountain snowpack. The newfound fungi appear to be so abundant, and so active, that they may force scientists to re-think the impact they have on the global climate.

Conventional scientific wisdom states that not much grows in the cold. So when a team of scientists went looking for life in samples taken in the chilly soil underneath mountain snow, they were surprised at what they found.

Microbiologist Steve Schmidt at the University of Colorado at Boulder led the team. "There were more fungi there under the snow than there are at the same spot in the summer. Which was pretty surprising," he says.

Mr. Schmidt's study appeared in a recent issue of the journal Science. There had been hints that something was going on under the snow. Earlier studies had shown something was giving off carbon dioxide and methane, two gases that microorganisms produce as they breathe and digest food. But fungus researcher Rytas Vilgalys at Duke University says when he read the study, he was surprised that there was so much activity.

"They're cooking underneath the snow pack," says Mr. Vilgalys. "We've been aware that certain mushroom species grow directly under the snow pack as it melts. But we didn't realize how active they actually were."

And it's not just their activity that's significant. Forty percent of the Earth's land mass is covered with snow at least some of the time. So if these snow-loving fungi are found to be widespread, University of Wisconsin biologist Jo Handelsman says global warming researchers will have to take note.

"A lot of the models about carbon dioxide haven't taken into account the high activity of the fungi during the winter," says Ms. Handelsman. "And carbon dioxide is thought to play a pretty important role in global warming, and has to be an important element in any good climate model."

Scientists will still have to figure out exactly how the newfound fungi fit into climate models. Mr. Vilgalys says as the planet warms, the fungi may produce more carbon dioxide, or they may store more.

Study author Steve Schmidt says he also has more work to do determine exactly what fungi his team found under the snow. He says some of the fungi will be familiar to anyone who's left fresh fruit sitting around too long. But many others are completely new.

"Many of them are organisms that had never been seen before," says Mr. Schmidt. "So they're basically forms of life that were unknown to science because, well, people hadn't really looked under the snow much."

Mr. Schmidt looked under the snow with new tools that researchers are using to map out the microscopic world better than ever before. Rather than relying on what they can see under a microscope, Mr. Schmidt's team and others examine soil and other places for DNA, the genetic material of all life on Earth.

Mr. Vilgalys says plants and animals have been the center of scientific attention for the last 200 years or so. But that's changing. "They had their age of discovery," he says. "And right now, biologists are in the middle of a major discovery phase to map out all the different species of microorganisms."

And Ms. Handelsman says there's more to discover than researchers had thought. "The diversity of microorganisms, both bacteria and fungi, is far, far greater than we ever suspected, based on the 100 previous years of microbiology," she explains.

Microorganisms out-number, and out-weigh, all the plant and animal life on Earth combined. Microscopic life in the soil makes nutrients in the air available for plants to live on, and recycles nutrients from dead plants and animals. So next time you're digging in the dirt, keep in mind what Ms. Handelsman says about that most common of substances.

"People who study soil have a reverence and respect for it that prevents us from calling it dirt," she says. "We wouldn't be here if it weren't for the life in the soil. Soil is a living organ. The bacteria and fungi in soil make the rest of life on Earth possible."

And scientists now know they're even hard at work in the cold soil under the snow. It's just another example of how much more we have to learn about the world right beneath our feet.