If you've never thought about how a whale's poo affects you, the time is now.

Why? Because the faecal matter of whales, oversized land mammals, seabirds and migrating fish plays a critical role in fertilising the planet.

Whales can act as a "distribution pump," transporting vital nutrients like phosphorus from the ocean floor to the surface, however their ability to do so has reduced by more than 75 per cent. Credit:Tribune

But a new study shows species decline and extinction is threatening the planet's age-old 'biogeochemical cycling' system (or nutrient recycling system), potentially weakening ecosystem health, fisheries and agriculture.

"Previously, animals were not thought to play an important role in nutrient movement," said Christopher Doughty, an ecologist at the University of Oxford and lead author of the study Global nutrient transport in a world of giants.