Why in News? 

Study on coral microatolls in the Maldives shows sea-level rise in the central Indian Ocean began earlier and progressed faster, challenging previous assumptions and affecting climate science & coastal policy. 

• Coral microatolls stop growing at low tide levels; making them natural recorders, recording sea-level changes.  
  • They provide long-term data, with some surviving for decades/centuries.  
• Maldives, Lakshadweep & Chagos saw a 30–40 cm rise in 50 years.  
• Environmental factors– El Niño and the Indian Ocean Dipole affect coral growth, aiding sea-level tracking.  

Sea-Level Rise (SLR)  

Causes: 

• B/w 2005–13, melting glaciers contributed nearly twice as much to SLR as thermal expansion; Greenland's ice loss increased seven-fold. 
• Changes in groundwater & land water sources add to rising sea levels; sea levels have risen ~ 21–24 cm since 1880.

Impact on Island Nations: 

• Coastal inundation, freshwater salinization, and habitat destruction; Maldives & Tuvalu face existential threats. 
• Saltwater intrusion/coral degradation harms agriculture and fish stocks; Kiribati & Marshall Islands face severe water shortages. 
• Intensified cyclones & floods damage infrastructure and economies; Hurricane Dorian caused USD 3 billion damage. 
• Erosion & reef destruction reduce tourism; Barbados faces declining tourism.  
• Warmer temperatures spread vector-borne diseases; forced migration leads to cultural erosion.