Earth’s largest conveyors of essential nutrients are disappearing.
Via Flickr user libraryems
One of the important functions large animals play in their ecosystems involves a behavior that they (and we) learn from birth: They don’t poop where they eat. As animals travel through their natural habitats—eating and pooping, eating and pooping—they are also distributing vital nutrients through wide swaths of land and sea.
But what happens as those large animals—like rhinos, whales, and elephants—begin to die off? As research published Monday in the Proceedings of the National Academy of Sciences and reported in the Washington Post demonstrates, losing those creatures’ poop can spell trouble for the environment.
A team of scientists led by Chris Doughty of Oxford University zoomed in on one important nutrient found in animal poop: phosphorus. Phosphates are essential ingredients in all life; they are necessary components in all DNA and in cell membranes. Now that there are fewer large animals, the scientists wondered, is our world less biologically productive?
“I wanted to know whether the world of the past with all the endemic animals was more fertile than our current world,” Doughty told the Post.
The research finds that the world is most certainly less fertile. Compared to the late Quaternary Period (1 million to 500,000 years ago), marine animals are moving phosphorous to the ocean’s surface at 23 percent of their former capacity. And land animals are moving phosphorus from sea to land at just 4 percent of their former rate.
In fact, the scientists warn that the world’s readily accessible supply of phosphate rock could run out in as few as 50 years. “How might civilization sustain agricultural productivity once those supplies are exhausted?” they wonder.
Not all of this decrease can be directly attributed to human activity. But the scientists say that humans are certainly not helping. The aggressive, large-scale hunting of whales (which began in the 17th century) means there are many fewer large marine mammals alive today to bring nutrients to the seas’ surface. Though some conservation efforts have helped to nurture formerly endangered whale populations, many are still threatened by human activity.
Via Flickr user Robbie Shade
The researchers also say that popular methods of raising livestock contribute to the decreased circulation of nutrients. Though large populations of livestock exist in many places—eating and pooping, eating and pooping—their movements are often constrained inside fences or indoor spaces. That means they’re not able to spread nutrients as widely as they once did.
The scientists suggest raising more animals in free-range environments, or in areas with a wider diversity of animal life (“such as cattle, sheep, horses, goats, and camels,” they write).
“A world bereft of large wild animals, whether they are whales, salmon, albatrosses, or elephants, is a less productive place—and one that has lost much of its magic," Joe Roman, a University of Vermont researcher who worked on the study, told the Post. "We can turn these effects around by restoring native populations of large vertebrates around the globe.”