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Abstract

Anthropogenic activities, in particular rising CO2 emissions, provoke ocean warming and acidification1,2, altering plankton habitats and threatening calcifying species3,4 such as planktonic Foraminifera (PF). Whether they can cope with these unprecedented rates of environmental change, through lateral migrations and vertical displacements, is unresolved. Here we show, using over a century of data from the FORCIS5 global census counts, that PF display evident poleward migratory behaviours, increasing their diversity at mid to high latitudes, and for some symbiont-barren species descending in the water column. Global PF abundance decreased by 24.24±0.11% over the last decades. Beyond lateral migrations6, our study uncovers intricate vertical migration patterns among PF species, presenting a nuanced understanding of their adaptive strategies. In projected temperature and carbonate saturation states for 2050 and 2100, low-latitude PF species will face physico-chemical environments that surpass their current tolerance. While these species might replace high-latitude ones through poleward shifts, this would radically alter low-latitude ecosystems. Our insights of PF adaptation during the Anthropocene reveals that 'migration is not enough', and has broader implications for the evolution of marine biodiversity under multiple stressors.