Geothermal/Hydrogen Power Solution
The basic idea is to use geothermal energy plants on the island to create large amounts of electrical energy, which would then be used to create hydrogen and oxygen from water. The hydrogen would be used in vehicles, fishing boats, and fuel cells as a power source, resulting in only water as a "pollutant". Obviously, this is a very idealized vision, and there will be other environmental costs. There can also be some sort of water supply system integrated with the fuel cells.
A similar system to this is being developed in Iceland, which get the majority of it's power from alternative sources (mostly hydro and geothermal), and is looking to integrate hydrogen power into their system.
A few links: