How Coastlines Shape the Extinction Risk for Marine Invertebrates

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TTo predict how communities of organisms will respond to environmental changes, scientists look to the deep past. Tracking the relationship between the evolution of biodiversity and change over millions of years provides a window into the factors that enable (or prohibit) organisms to manage change. In an article published yesterday in Science conducted by researchers at the University of Oxford, the risk of extinction of marine invertebrates was linked to the configuration of the coasts.

The researchers examined about 300,000 fossils representing more than 12,000 genera of oceanic invertebrates that lived over the past 540 million years on shallow continental shelves. By reconstructing the layout of the continents over the life of the organisms, they estimated the geometry (both shape and orientation) of the coastlines they inhabited. Then, by statistically modeling the relationship, they tested the hypothesis that shoreline geometry influenced extinction risk.

The data showed that organisms inhabiting north-south oriented coastlines, such as today’s North American coastlines, had a better chance of long-term survival when conditions changed. The study authors hypothesized that north-south coastlines provide a corridor for organisms that rely on shallow waters to migrate and stay within their tolerance ranges when climate or other conditions change.

Read more: “Our boiling seas”

Organisms that lived along islands, inland sea lanes, or east-west oriented coastlines, such as the present-day coasts of the Mediterranean, were at a disadvantage when conditions changed. Migration to newly adapted habitats was probably impossible, short of crossing the ocean. Thus, these coastal invertebrates, which have limited abilities to travel long distances, found themselves confronted with what the researchers dubbed “latitudinal traps”.

“Groups that are trapped at one latitude, because they live on an island or on an east-west coast, for example, are unable to escape inappropriate temperatures and are more likely to become extinct as a result,” study author and Earth scientist Erin Saupe explained in a statement.

During mass extinction events or particularly warm periods, the role of shoreline geometry in extinction risk was more pronounced. Geographic constraints imposed by the shape and orientation of coastlines appear to have amplified their influence on extinction during periods of high environmental stress.

“This work confirms what many paleontologists and biologists have suspected for years: the ability of a species to migrate to different latitudes is vital for its survival,” concluded lead author and earth scientist Cooper Malanoski in a statement.

These patterns detected over millions of years could apply to modern species. Organisms living in the “latitudinal traps” of east-west coasts or islands may be particularly vulnerable to dramatic changes in conditions.

The study calls for attention to shoreline geometry to predict and mitigate how species will cope with continued climate change.

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Main image: Erik Lukas / Ocean Image Bank

• Devin Reese

  Published on January 16, 2026

  Devin Reese is the editor-in-chief of Natural history and a science writer based in Alexandria, Virginia.