The average island economy is only one-fifth the size of a mainland state, making them vulnerable to overreliance on a particular industry. Notably, a bankruptcy filing of a single mega-resort in the Bahamas weighed enough on its economy to result in a negative sovereign credit outlook from S&P.
Heavy reliance on tourism can prove doubly problematic in regions vulnerable to climate change.
"Coral bleaching, which reflects rising sea temperatures, appears to be causing a decline in fishing activity in the South Pacific, including in the Fiji islands. Temperature changes are also leading to a redistribution of tuna resources out of islands in the Pacific into higher latitudes, with serious economic consequences," Gill said.
Due to their typically small size, islands may also be more vulnerable from a military or geopolitical perspective. The island of Cyprus, for instance, remains divided, although reunification could generate extra GDP growth.