Small island states in the Pacific are opening a new front in the fight against rising seas, to secure rights to an ocean area bigger than the moon that is home to billion-dollar fish stocks.

States from Kiribati to Tuvalu are mapping their remote islands, scattered across the ocean, in a bid to claim permanent exclusive economic zones (EEZs), stretching 200 nautical miles (370 km) offshore, irrespective of future sea level rise.

As global warming pushes waters higher, Pacific nations fear their islands could be swamped, shrinking their EEZs and rights to fishing and mining within their boundaries — so they are trying to lock in existing zones now.