Repost Natural World News - October 27, 2015
(http://www.natureworldnews.com/articles/17797/20151027/loss-animals-poop-disrupts-nutrient-cycles-new-study-shows.htm) 

By Samantha Mathewson

Believe it or not, we rely more heavily on animals' feces than you would think. Essentially, the poop from wild animals keeps the planet fertile by transporting nutrients deep from the ocean floor all the way to mountain tops, a recent study revealed. This makes the extinction of large animals even more devastating.

Animals' poop plays a key role in keeping the planet fertile. When animals go extinct, natural nutrient cycling from deep ocean waters to high mountainous areas dwindles. (Photo : Wikimedia Commons )

"This once was a world that had ten times more whales; twenty times more anadromous fish, like salmon; double the number of seabirds; and ten times more large herbivores--giant sloths and mastodons and mammoths," Joe Roman, a biologist at the University of Vermont (UVW) and co-author of the recent study, said in a news release. "This broken global cycle may weaken ecosystem health, fisheries, and agriculture."

(Photo : Diagram from PNAS; designed by Renate Helmiss)
This diagram shows an interlinked system of animals that carry nutrients from ocean depths to deep inland -- through their poop, urine, and, upon death, decomposing bodies.

The ability of animals to readily transport nutrients over a wide area has significantly decreased since the mass extinction following the end of the last ice age, according to researchers from UVM. This proves that animals act as major "distribution pumps" that transport large amounts of nutrients to areas that would otherwise be less productive, including surface waters and remote inland areas. 

Basically, the more animals eat, the more they poop. When animals eat a lot of plant matter, they release nutrients from vegetation through processes of digestion. Then they transport these nutrients from feeding areas, or nutrient-rich "hot spots," to more remote areas. The valuable nutrients are introduced to scarce areas when animals excrete poop and urine, or when their bodies decompose after death, the release explained.

So how do nutrients cycle through different ecosystems? Marine animals transport vital nutrients, such as phosphorous, to the surface from otherwise unreachable areas deep within the ocean. Then, seabirds and fish spread the nutrients across seas, up rivers and deep inland, where land animals then help transport the nutrients to high mountainous areas, researchers explained. Humans, in turn, depend on these fertilized ecosystems to perform natural life-sustaining functions, such as agriculture or carbon storage.

"Phosphorus is a key element in fertilizers and easily accessible phosphate supplies may run out in as little as fifty years," Chris Doughty, lead author and an ecologist at the University of Oxford, explained in the release. "Restoring populations of animals to their former bounty could help to recycle phosphorus from the sea to land, increasing global stocks of available phosphorus in the future."

From their study, researchers concluded that this animal-powered nutrient pump has decreased to six percent of its former capacity to spread nutrients away from concentrated areas on both land and sea, according to the release.

"But recovery is possible and important," Roman added, as he continued to explain that bringing back herds of North America bison is a prime example of how humans could rejuvenate nutrient cycles.

"The typical flow of nutrients is down mountains to the oceans," Roman explained in the release. "We are looking at ways that nutrients can go in the other direction--and that's largely through foraging animals. They're bringing nutrients from the deep sea that could eventually reach a mountain in British Columbia."

Their study was recently published in the Proceedings of the National Academy of Sciences. 

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