We tend to think of poop as problematic. Most discussions about it center on how to get rid of it more effectively, and we do so by concentrating it, treating it in various ways, and pushing it far, far away. But before people roamed the Earth and built sewer systems, animals just went wherever they wanted.

Well, not exactly wherever. Animals tend to be particular about where they defecate, doing it away from where they eat and sleep. This instinctive behavior not only keeps them healthy, but it spreads nutrients around their habitats — which is the exact opposite of what people do.

This nutrient movement turns out to be incredibly important for healthy ecosystems. A recent study published in the Proceedings of the National Academy of Sciences examined how both the loss of large mammals over time — and the significant limitation of their movements — has made the environments where they used to roam poorer.

Why study such a thing? "I wanted to know whether the world of the past with all the endemic animals was more fertile than our current world," lead study author Chris Doughty of Oxford University told The Washington Post.

Turns out that previous eras of history were more nutrient-rich, at least when it comes to phosphorus, a key nutrient that researchers focused on. And while smaller animals can impact this nutrient transport, the researchers point out: "... large animals disproportionately drive nutrient movement," meaning smaller creatures can't make up for what big creatures don't do.

Humpback whaleWhales fascinate us with their playful breaches and their haunting songs, but what goes on under the water is even more important in the grand scheme of things. (Photo: Whit Welles/Wikimedia Commons)

Case in point: Earth's largest living mammals are whales. Habitat destruction and hunting has brought the populations of most major species down into the single digits. In the past, whales brought what researchers estimate was about 750 million pounds of phosphorus yearly from the deep ocean to the upper levels. (They feed down below and poop near the surface.) That's compared with about 165 millions pounds today — and that's after the recent years' recovery of some whale populations.

Overall, the researchers found: "The vertical movement of phosphorus (P) by marine mammals was reduced by 77 percent and movement of P from sea to land by seabirds and anadromous fish was reduced by 96 percent, effectively disrupting an efficient nutrient distribution pump that once existed from the deep sea to the continental interiors."

We know that human beings are quickly changing Earth's ecosystems, with many unintended consequences — and many of those effects are just now being studied. When it comes to large animals, poop affects the whole environment (in a good way), and with only a few exceptions, we have fewer of them left every year.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.