Nearly 20% of species residing in UNESCO’s world heritage marine sites live in unsuitably warm waters

Nearly 20% of species residing in UNESCO’s world heritage marine sites live in unsuitably warm waters

Sub: Sci

Sec: Biodiversity  

Context:

• Nearly 20% of species in 21 UNESCO World Heritage marine sites are living at or beyond their thermal limits, making them vulnerable to temperature changes.
• The report, Engaging Communities to Safeguard Ocean Life, highlights the effects of ocean warming on marine species and ecosystems.

Key Findings:

• Species Affected: 881 species out of 4,406 mapped are at risk, including: 342 fish species, 135 algae species, 76 mollusc species.
  • 5 mammal species: Atlantic bottlenose dolphin, West Indian manatee, southern elephant seal, True’s beaked whale, Crabeater seal
  • 7 shark species: Lesser sandshark, Whitespotted eagle ray, Caribbean reef shark, Southern stingray, Krefft’s ray, Lemon shark, Yellow stingray
• Thermal Limit Hotspots:
  • Belize Barrier Reef: 53% of species living near their thermal limits.
  • Coiba National Park (Panama): 26.6% of species at risk.
  • Everglades National Park (USA): 24.4% of species at risk.
  • Banc d’Arguin National Park (Mauritania): 23.9% of species at risk.
  • Sundarbans (Bay of Bengal): 19.8% of species living beyond thermal limits.
• Ocean Heat Trends:
  • Global sea surface temperature (SST) is 1°C higher than 140 years ago.
  • Ocean heat content has impacted all the six major oceans since 1998. The Southern Ocean has seen the most significant warming since 1998.

Implications of Ocean Warming:

• Adaptation or Migration:
  • Species may migrate to cooler waters, but some may not adapt effectively.
  • Tropical species are particularly vulnerable due to limited recent exposure to high temperatures.
• Reproductive Stress:
  • Warm waters impair reproductive rates (e.g., female sperm whales struggle to conceive).
  • Stress levels in marine mammals rise, reducing survival rates.
• Food Chain Disruption:
  • Species like North Atlantic right whales face food shortages due to prey migration.
  • Key habitats for fish, lobsters, oysters, and crabs are shifting.
• Oxygen and Nutrient Cycles:
  • Changes in water movement reduce oxygen levels and nutrient circulation.
  • Altered bacterial behavior impacts water and atmospheric characteristics.
• Pathogen Vulnerability:
  • Migrating species are exposed to new pathogens, increasing disease risks.