As the oceans warm, many marine species are forced to shrink their habitats as coastlines cut off their access to the cooler, safer waters.
If that escape fails, losses extend beyond wildlife, disrupting food supplies, livelihoods, and coastal protection provided by healthy oceans.
Some coastlines block escape.
researchers oxford university I found a simple pattern. In shallow waters, east-west coastlines are at high risk of extinction, while north-south coastlines provide safer evacuation routes.
The study was led by Dr. Cooper Malanosky, who used fossils to map the extinction. His research focuses on how geography and climate set boundaries for marine life, especially during times of rapid warming.
Simple map-based clues offer conservation planners a new way to identify marine populations that may have exhausted their habitat.
Fossils reveal long-term risks
To trace the Phanerozoic extinction of complex life over the past 540 million years, researchers relied on fossils that occurred around the world.
The research team analyzed more than 300,000 fossils from shallow-sea animals spanning more than 12,000 genera, a group of closely related species.
The fossils matched paleogeography – Reconstructing the ancient positions of continents and coastlines – so each mountain range is preserved in its original environment.
Statistical models then compare who survived on different coastline layouts, but the fossils still exclude soft-bodied groups and some areas.
Species are stuck by latitude
Along the east and west coasts, herds of animals can migrate long distances while remaining near the same latitude.
The main sources of risk are latitude trapwhere it is difficult to move north or south, even if the nearby water is cold.
Islands and inland sea routes create dead ends because they block direct routes to open water and cooler areas of land.
As warming moves away from favorable conditions, the geometry transforms local problems into transgenerational, species-level risks.
move north or south
Evidence so far suggests that survival depends on species being able to migrate to cooler waters as the climate warms.
As the north and south coasts cross the latitudinal zone, the temperature changes, and organisms remain within them, slowing their migration. heat resistance – A safe range for bodily functions.
Professor Erin Thorpe from the University of Oxford said: “This reduces the risk of extinction.”
Global warming and extinction risk
Species in these traps may also be unable to mix genes with populations in colder waters, limiting their adaptation if changes arrive quickly.
The risk of extinction due to confined coastlines increases during mass extinctions and during periods of warming.
That pattern will continue to strengthen Interval of high temperature periodan episode of unusually warm global climate in which ocean temperatures rise above what many species can tolerate.
“This shows how important paleogeographical context is, allowing taxa to track their preferred conditions during periods of extreme climate change,” Dr. Malanosky said.
If modern warming accelerates, coasts that limit latitudinal variation could create the same bottlenecks for coral reefs and fisheries.
the sea comes to a dead end
Some ancient oceans had coastlines packed with inlets and inland seas. model We associate that layout with higher vulnerability.
Plate movement can close seaways and open others, changing which edges connect to cold water and which edges are enclosed.
Modern examples include the Mediterranean Sea and the Gulf of Mexico. In these areas, the complex coastline and neighboring lands provide indirect travel routes.
As continents continue to move, the same regions may flip from corridors to traps, changing the long-term risk of settlement systems.
The limits of fossils still remain
Even with huge fossil samples, gaps remain, and by 2024 review They warn that preservation will bias which species emerge.
Hard shells are more likely to fossilize because the minerals do not rot easily, so animals with soft bodies may disappear without leaving a clear record.
Time bins can also blur rapid events, as layers can contain fossils from thousands of years old mixed into a single snapshot.
These limitations mean that the shoreline signal is strongest as a relative warning rather than an accurate prediction of a single species.
Seeds change
Modern warming is already changing ocean ranges. Intergovernmental Panel on Climate Change report summarizes patterns across many studies.
Since the 1950s, typical poleward migration has been 32 miles per decade near the surface and 18 miles per decade near the ocean floor.
Ocean currents, oxygen levels, and the shape of the ocean floor can dictate their movements, so some populations must choose between deeper oceans and new latitudes.
For animals living in bays or closed oceans, such options may not exist, and local extinction can occur rapidly.
Protection from shoreline traps
Long-term fossil studies have shown geographical features. range Particular attention should be paid to narrow distributions, as they often predict who will disappear.
Administrators can map coasts that provide direct north-south routes. Because this corridor allows residents to track temperatures without having to cross land.
In areas where barriers prevail, conservation may need to focus on local refugia, as nearby cool habitats may not be accessible during heat waves.
There are still trade-offs with this approach, as while it may buy time by reducing fishing and pollution, it does not remove geographic locks.
Taken together, fossils, coastlines, and climate history point to migration as a means of survival that geography sometimes precludes.
Future studies may examine populations in closed basins, while conservation plans will consider areas where warming leaves no clear exit.
The research will be published in a journal science.
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