160-10 Late Pleistocene Marine Ecological Change and Implications for Modern Climate Change Along the Southern California Coast

Abstract:

Earth has experienced significant climatic fluctuations through geologic time, including warming events of varying duration and intensity. These events leave behind evidence in the fossil record that can provide valuable insights into how biodiversity responded to past warming events, helping us better understand the ecological consequences of future warming trajectories.

The impacts of climate warming in the marine and terrestrial realms can be very different, resulting in highly variable extinction and survival patterns across different environments and taxonomic groups. Southern California serves as an ideal location to study potential linkages between land and sea in the context of climatic variability due to its excellent Late Pleistocene record, which preserves everything from terrestrial megafauna to marine micromolluscs. Several studies have shown vegetation and megafaunal responses to rapid climatic shifts during the last deglaciation, including range shifts and extinction. However, less is known about how coastal marine species responded to climate forcing, particularly whether they experienced extinction or avoided extinction through range shifts, local persistence, or survival in refugia.

Here, we investigate Late Pleistocene coastal molluscan assemblages from Southern California to examine how marine biodiversity responded to the Last Interglacial warming event. We find no major extinction among marine molluscs during this time. Instead, thermally anomalous species preserved in the fossil record provide evidence for an escape hypothesis, in which province-restricted taxa tracked suitable environmental conditions through range shifting. Range shifting taxa could establish populations in shallow, protected warm-water habitats that likely acted as refugia during warming phases, despite climatic instability on the open shelf. As much as 10% of Late Pleistocene molluscan taxa in Southern California exhibited this migratory response, suggesting that marine coastal ecosystems were dynamic and composed of taxa readily shifting their distributions. In contrast topographic complexity on land generates local entrapments, and increases the potential for local extinction. 

Evidence from the fossil and stratigraphic record provides valuable insight into the potential impacts of ongoing climate change and biodiversity loss, linking past ecosystem responses to modern and future warming. These findings also highlight the ecological significance of warm-water embayments or protected habitats as shelters for migratory species during climate change.

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.