[NoPie]

Santa Cruz where most of the local population lives gets half of its water from desalination plant.

Desalination is already cost-effective and can provide water for tourists if needed. They would just need to build a desalination plant in the south.

Electricity already is largely generated by wind, solar and tide.

Air transportation probably causes the biggest pollution.

Apart from that such tourism is very sustainable. It provides value to people who need to go on holidays. It doesn't matter if the food and necessities are imported because tourists would have consumed the food anyway if they had stayed at home.

While it causes unsustainable rent increases to local population, that can be managed somehow. Maybe give subsidies to them by using the profits from tourism. Tourism tax is not unusual invention in many places.