I'm in the middle of a week at the Fall Meeting of the American Geophysical Union, in San Francisco. This is typically a whirl of talks, posters, refreshment breaks (coffee in the morning, beer in the afternoon) and throngs of geoscientists. I typically don't cover the meeting like a journalist does, although I share the press room with them. A lot of what I seek out is background stuff that I hope is ahead of the cutting edgeat least, it's ahead of my cutting edge. A talk I saw yesterday was not like the others.
Manny Gabet, of San Jose State University, has been studying the odd landscape features known as mima ("meema") mounds. They're piles of dirt, a meter or two high, and range in area from dinner-table to living-room size. They occur bunched up together in big groups, and are widespread in the American West. Gabet cited two special facts about them: they're found where the winter rains regularly saturate the ground, and they're occupied by pocket gophers, one on each mound, with the unusual habit of pushing the dirt from their burrows uphill. He made a computer model of a bunch of gophers and set them loose on a flat computer landscape, showing that their behavior, over several centuries, turned the ground into fields of mima mounds.
The advantage of a mound is that it sits above the winter rains, making large areas of marginal land inhabitable for gophers. Gabet told us that by his reckoning, mima mounds are the largest set of animal-made structures on Earthother than our own, of course. It intrigues me that a single change in behavior brought this aboutpushing dirt uphill instead of downhill. That probably arose from a very small genetic change, one that doesn't make a difference east of the Mississippi, where mima mounds aren't found.
Mima mound field from the air Washington Department of Natural Resources