When you hear "sea level rise," you probably picture flooded streets and disappearing beaches. A new study in Nature Ecology & Evolution looks at what moves into that new water. The team modelled 122 non-native marine animals that are already established outside their home ranges. They found that more than two-thirds of the coastline flooded by mid-century and late-century sea level rise could become suitable habitat for them. That's 290,000 to 470,000 square kilometres, somewhere between the size of Italy and Sweden. The most exposed regions are the eastern United States, the Gulf of Mexico, the North Sea coast, southeastern China and northern Australia, with mid-latitude estuaries as the biggest hotspots. We look at the species in line, including Chinese mitten crabs, Pacific oysters, Asian tiger shrimp and the European green crab that Atlantic Canada already knows well. We also cover what the model can and can't tell us, and why early monitoring is the best defence.
Then we listen in on sharks. Researchers at Florida Atlantic University played low-frequency sounds to wild blacktip sharks off Palm Beach County and filmed their reactions with a drone. The sharks responded from up to 243 feet (74 metres) away and turned sharply away from the speaker, showing they could tell which direction the sound came from. More than 70% of the reactions happened in the acoustic far field, where free-swimming sharks had never been shown to respond. We talk about how sharks hear without a swim bladder, why the low frequencies they react to overlap with shipping noise, and what this study doesn't tell us yet.
Next time you see a sea level rise map, ask: what moves in? And next time you see a shark story built around smell, ask: what are they hearing?
Takeaways:
More than two-thirds of newly flooded coastline could become suitable habitat for 122 established invasive marine species, according to a new model.
The area at risk is 290,000 to 470,000 km², roughly the size of Italy to Sweden, under a moderate emissions scenario.
Mid-latitude estuaries face the highest risk. They're nurseries for fish and shellfish, and they're also where ports and aquaculture bring invaders in.
Suitable habitat is one step in an invasion. A species still has to arrive and survive, which is why early monitoring matters.
Blacktip sharks reacted to sounds from up to 243 feet away and could tell which direction the sound came from.
The sharks reacted most to sounds between 100 and 400 Hz and ignored a 10 kHz control tone.
Commercial shipping noise is mostly below 500 Hz, the same range these sharks hear best.
What you can do: learn and report the invasive species on your coast, clean, drain and dry your gear between waters, and count ocean noise as a conservation issue.
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