Scooping that poop is more important than you thought.

Dog poop turns out to have a pretty big environmental impact. If you think that two in five households in the U.S. have at least one dog, and that about forty percent of Americans don't clean up after their pooches, well, all that poop really adds up. In fact, it's what scientists call the Fido hypothesis.

They conjecture that a lot of that waste ends up in waterways. Recent studies, in fact, suggest that dogs are in third or fourth place on the list of contributors to bacteria in water. Talk about gross--fecal matter is full of disease-causing bacteria like E. Coli, salmonella, and giardia.

Now that bacteria-tracking methods have gotten better, scientists estimate that in some areas, 20 to 30 percent of the bacteria in a stream comes from dogs. And the thing is, pollution from dogs is relatively easy to control. All you have to do is scoop when they poop.