Nature's Recycling System: The Remarkable Role of Feces in Ecosystems and Fertilization

Does it disgust you to talk about. poop? Yet, in nature, excrement is very useful to the environment, to the life of numerous animals and to the development of certain ecosystems. nature teaches us the message invoked in the lyrics of one of Italy's greatest songwriters, Fabrizio De André. Today our journey begins with a famous phrase of the Genoese man from the famous song "Via del Campo".

From diamonds nothing is born, from dung flowers are born.

Dung beetles, with around 6,000 species, are well-known for feeding on the fibers and nutrients in feces. They create balls of dung, which they either lay eggs in or consume leisurely. These beetles were linked to the Egyptian scarab god Khepri, who moved the Sun across the sky.

Seabird colonies produce guano, a mix of feces and uric acid paste, which contains substances like nitrogen that end up on land, in the air, and in the sea. Tiago Osorio Ferreira from the University of São Paulo and his team estimated that seabirds produce 591 thousand tons of nitrogen and 99 thousand tons of phosphorus yearly. Guano serves as fertilizer for plants and food for other organisms. For instance, larvae of chironomids on Stora Karlsö Island feed on seabird droppings and later become food for house martins.

Stef Bockhorst of Vrije Universiteit Amsterdam found that penguin and elephant seal colonies in the Antarctic Peninsula are biodiversity hotspots, with nitrogen-rich environments supporting mosses, lichens, and invertebrates. Candida Savage from the University of Otago observed that corals near seabird colonies grow more due to nitrogen benefiting symbiotic algae.

Whale fecal plumes, rich in iron, act as a nutrient transport system called the "whale pump." These plumes benefit microscopic algae, which then support the entire food chain. Conversely, hippos are significant silicon pumps, consuming it from plants and releasing it into African rivers, benefiting diatoms and single-celled algae.

Endozoochory is a process where plants disperse their seeds through animal ingestion and subsequent release in feces. Elephants can carry seeds up to 65 km, while birds carry them even farther. Óscar M. Chaves and colleagues analyzed over 315,000 seeds from 98 plant species expelled by howler monkeys. Some plants, like Cerbera floribunda, rely on specific animals, such as the Australian cassowary, for seed dispersal.

Humans have also utilized feces, such as manure and seabird guano, for fertilization purposes. Fossilized feces (coprolites) provide scientists with insights into the diets of living animals, extinct dinosaurs, and ancient humans.