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Warming Oceans and Changing Marine Habitats
Context:
Human activities release billions of tonnes of greenhouse gases into the atmosphere annually, trapping heat from the Sun and causing the Earth’s temperature to rise.
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- Over 90% of this additional heat is absorbed by the oceans, leading to alarming increases in marine temperatures.
- Estimates suggest that since the onset of the Industrial Revolution over 250 years ago, ocean temperatures have risen by more than 1.5°C.
The Impact on Marine Life
- Marine organisms are highly sensitive to temperature changes due to their narrow “thermal safety margins,” which represent the small difference between the environmental temperature and the maximum temperature they can tolerate.
- With limited ability to escape rising temperatures, such as migrating to cooler depths—which is not always feasible—thousands of marine species face unsafe conditions as the planet continues to warm.
- This could impair their survival and reproduction, leading to population declines or even local extinctions.
- Simultaneously, warming oceans are creating thermal opportunities, allowing some species to move into areas previously too cold for them.
- However, this shift can disrupt ecosystems and cause mismatches between fish stock locations and fishing communities, potentially affecting local economies and food security.
Understanding Thermal Changes
- As scientists studying the effects of climate change on species, ecosystems, and humans, they analysed data from 21,000 marine species alongside future climate projections. Their model examined two key aspects:
- The emergence of thermal opportunities.
- The risks posed by exposure to warmer waters.
Key Findings
- Thermal Opportunities: These emerge earlier and more gradually, primarily in temperate and polar regions, allowing species to colonise new habitats.
- These opportunities are expected to increase until 2050, even with rapid reductions in greenhouse gas emissions, and persist through the century.
- Thermal Threats: Risks from exposure to unsafe temperatures arise later but more abruptly, particularly in tropical ecosystems.
- After 2050, these risks could escalate significantly, especially if global warming exceeds the 2°C threshold set by the Paris Agreement.
- Even under rapid warming, new suitable habitats could remain available for decades, providing species time to migrate and adapt.
- This could prevent declines or extinctions for some species and offer economic or food security benefits to humans.
