Warming, thresholds and extinctions: lessons from past hyperthermals on land and at sea

The Anthropocene is characterized by an accelerating biodiversity crisis, with extinction rates far exceeding natural background levels and early warning signs reminiscent of past mass-extinction trajectories.The magnitude and pace of disruption raise the prospect of long-lasting, potentially irreversible ecological and evolutionary consequences.To place the present crisis in a long-term context, we synthesize fossil evidence from major intervals of climatic instability, such as the Permian/Triassic catastrophic extinction, the Eocene/Oligocene transition, and the onset of Northern Hemisphere glaciation.These events reveal how rapid warming, physiological thresholds, and cascading ecosystem disruptions have repeatedly reshaped life on Earth in both marine and terrestrial realms.However, the modern crisis differs fundamentally from ancient analogs: direct human pressure now compounds climatic stressors.On land, habitat destruction, fragmentation, exploitation, and the unprecedented velocity of contemporary warming severely limit the capacity of species to track shifting climatic niches.Together, these forces elevate extinction risk at the levels observed in past natural hyperthermal events.This perspective argues for conservation strategies grounded in the long-term behavior of the Earth system.Lessons from deep time, including threshold dynamics, rates of change, and the impact of functional losses, highlight the urgency of policies that reduce warming, secure ecological connectivity, and curb direct anthropogenic impacts.Such approaches offer the most promising route to stabilizing biodiversity, maintaining ecosystem functioning, and safeguarding the well-being of future generations.