Arctic defaunation initiated a cascade of mammal–plant interaction shift through dispersal dynamics
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Most large terrestrial mammals are declining rapidly under climate change, but whether their loss triggers broader ecosystem collapse remains unresolved. Using sedimentary ancient metagenomics, we reconstructed ecological networks and community turnover of Arctic mammals and plants over the past 25,000 years. We identified rewiring of mammalian interactions between 25–15 ka initiating cascading effects, culminating in the steppe–tundra’s transition to open woodland by 10 ka. Incorporating traits analysis, we revealed this prolonged process was buffered by long-distance seed dispersal—especially via megaherbivores—but loss of dispersal due to defaunation ultimately drove steppe–tundra collapse. Trophic interactions by megaomnivores and small mammals were insufficient to prevent turnover. Our findings identify resilient interactions and key megafaunal functions, offering insights for targeted rewilding to restore Arctic ecosystem functioning.
