Lack of Large Animal Poop Is Hurting Earth’s Ecosystem

The research is based on a series of recent studies on large creatures, coupled with mathematical models to estimate how nutrients move across land and oceans, and how this has changed along with declining animal populations. In particular, their poop.

A new study shows that whales and outsized land mammals, as well as seabirds and migrating fish, play a vital role in keeping the planet fertile by transporting nutrients from ocean depths to mountaintops – but their populations are plummeting.

“It was a relatively simple process”, study co-author Joe Roman of the University of Vermont told The Washington Post.

Overall, the team’s calculations show that the animal-powered nutrient dump has dropped eight percent from what it once was-before the last ice age’s extinction of 150 “megafauna” animal species.

It’s probably no surprise to learn that humans have had a hand in disrupting this ecosystem balance.

These deep-diving animals’ feces spread the nutrient phosphorous around the ocean, so declines in numbers result in a fall in nutrient transport. For example, the new study notes that restoring whale populations could help increase the ocean’s capacity to absorb climate-warming carbon dioxide.

“Animal digestion accelerates cycling of nutrients from more recalcitrant forms in decomposing plant matter to more labile forms in excreta after (wild or domestic) herbivore consumption on land”.

Animals were previously thought to play a minor role in the movement of nutrients in the environment with most of it being carried out by weathering of rocks and the actions of microorganisms like bacteria and fungi.

The situation is similar when it comes to moving nutrients from the sea to the land, such as fish being plucked from the ocean by seabirds and ending up as poop at nesting sites, or when salmon swim upstream and die, their rotting bodies being absorbed into the terrestrial ecosystem. This view assumed that the role of animals was minor, and mostly that of a passive consumer of nutrients. Now, only a few thousand remain.

This is bad news for the world’s phosphorous supply, which could run out in as little as 50 years, lead author of the study Christopher Doughty said in a statement.

The recovery of animals that could once again be instrumental in the transport of nutrients is possible, the scientists say. “Restoring populations of animals could help to recycle phosphorus from the sea to land increasing global stocks of available phosphorus in the future”.

“These nutrients can enhance the growth of algae, invertebrates even fish”, Roman said.

Previously, whales and other marine mammals moved a global total of around 340 million kg of phosphorous a year from the depths to the water surface, but now transport just 75 million kg of phosphorous (about 23% of their former capacity). “That’s achievable. It might be a challenge policy-wise, but it’s certainly within our power to bring back herds of bison to North America”.

“One is the inherent value of the species that we want to keep around, and the second part is that they play important roles ecologically”, he says. “However, in the past, we hypothesize that it would have been at least an order of magnitude larger than today”.