In the vast machinery of life, few roles are as humble—and as irreplaceable—as those played by the animals that disperse seeds. Their work begins with the unheralded act of consumption: a monkey swallows a fig, a tapir noses through fallen fruit, a bird flies off with a berry in its beak. What follows is a journey through gut and forest, culminating in the drop of a seed onto fertile soil, sometimes miles from where it began. For millennia, this simple, intimate cycle has been the unseen engine of the world’s forests.
But now, that cycle is breaking down.
A sweeping review published in Nature Reviews Biodiversity finds that the global decline of seed-dispersing animals—birds, bats, monkeys, fish, and others—is imperiling not just biodiversity, but the very resilience of ecosystems, reports Kristine Sabillo Guerrero. These creatures, many of them large and wide-ranging, are vanishing under the pressures of deforestation, hunting, invasive species, and climate change. The consequences unfold slowly, almost imperceptibly, over decades. But they are no less devastating.
Without their animal couriers, trees struggle to regenerate. Some, like the Brazil nut, depend on a single species to move their seeds. Others rely on long-distance dispersal to track the shifting climate. Without this movement, forests fragment. Diversity thins. Regrowth slows. Carbon stocks diminish. A tree that should have risen never takes root.
The world has rightly mourned the bees. Yet seed dispersers, no less vital, have slipped from public consciousness. Their decline has halved the number of seeds dispersed far enough to help plants adapt to a warming planet. Forests, once capable of healing themselves, are losing that ability.
Mauro Galetti, a co-author of the study, called these creatures “unknown heroes.” Their heroism, it seems, has gone unrecognized for too long. The tragedy is not only that we are losing them, but that we may not know what we’ve lost until it is too late. Forests will grow quiet—not all at once, but seed by seed, life by life, memory by memory.
Some absences are so gradual, they are mistaken for the natural order of things.
