My guest this week is Duncan Patten (http://landresources.montana.edu/Department/Patten.html), an ecologist with whom I discuss agricultural pollution, the importance of riparian strips along streams, fracking, and yes, rain barrels, all under the umbrella topic of groundwater. Duncan spent thirty years at Arizona State University before “retiring” to Montana, where he is now a research professor in the department of Land Resources and Environmental Sciences, the director of the Montana Water Center (http://watercenter.montana.edu/), and member of an EPA panel charged with studying how hydraulic fracturing (a.k.a. “fracking”) might affect public health and the environment. But before all that, Duncan got a doctorate in ecology at Duke University in 1962, and he starts this show by defining ecology as the study of how organisms affect their environment and it affects them. In other words, ecology is about relationships. That theme ran through our conversation, stitching together its seemingly disparate topics. I set out to learn about groundwater, but one of the first things Duncan taught me was that you can’t really isolate groundwater from surface water, nor from the plants that depend on it, nor the animals that depend on those plants. Wells tap groundwater, but put enough of them (or too many) near a river or stream, and the levels in that waterway may drop. Rain barrels seem like a no-brainer, but their use benefits groundwater (maybe) at the expense of surface water. The cottonwoods and willows that line so many western waterways transpire vast amounts of water (up to 350 gallons per tree per day), but cutting them down to increase river flow may backfire, as one Arizona town discovered to its dismay. The loss of those trees affected all the other plants along the stream, as well as the fish in it and the humans who like to catch those fish. The repercussions are felt in seemingly distant spheres because, as Duncan points out, all of these things are interrelated. The Arizona town that cut down ten miles of streamside cottonwoods got a harsh object lesson in ecology. They learned that the trees, the water, and the fish are all related; they depend on each other, and we depend on them. Check the post on the blog, The Manic Gardener (http://themanicgardener.com/), for more information and resources on this topic.