When whales disappear, so does their ecosystem-sustaining poop
Francois Gohler/Science Source

When whales disappear, so does their ecosystem-sustaining poop

Humans have been bad for blue whales. As many as 350,000 of the giant mammals (pictured) once plied the oceans; now, only a few thousand are left. Although removing such creatures from ecosystems can have a host of effects, a new study draws attention to one in particular: There’s a lot less poop getting spread around the planet. In the research, published online today in the Proceedings of the National Academy of Sciences, the scientists describe how losing these animals and other “megafauna” has upset a global cycle that once passed large amounts of nutrients like phosphorus from the ocean depths where large marine mammals like blue whales often feed into the sunlit surface waters where seabirds or migrating fish like salmon browse. As those fish swam back up the rivers where they were born or the birds returned to dry ground, the nutrients went with them, incorporated into their bodies or excreted, eventually feeding a host of terrestrial organisms. In turn, those animals’ own waste—and eventually decomposing bodies—helped spread the nutrients even further, fertilizing the interior of continents, the scientists say. In all, the researchers used a set of mathematical models to reveal that today animals only have about 6% of their former capacity to move such nutrients away from “hot spots” and across the oceans and land. Such a loss may continue to weaken ecosystem health, fisheries, and agriculture, leaving them less naturally productive than they might otherwise be. Protecting whales, migratory fish, and seabirds could make a difference in restoring, at least somewhat, the nutrient pathway, the scientists say.