first of all we need to understand climate change...segregate climate change effects from other environmental dynamics... assess the influence (both positive and negative and where other dynamic are carefully excluded) of climate change on biological productivity and agriculture... and finally we can think of possible best solution
what the Pacific Islands is concerned I think that there are in general no issues of food insecurity. They can come up during disaster events. Some Pacific Island countries have severe challenges with Non-communicable diseases, which -among other reasons- come from over-nutrition and malnutrition, but generally not from under-nutrition. Leaving this aside food security can be strengthened by selecting crops that are better suitable for a changing climate.
It is very important to introduce traditional varieties which is resilient to climate change. Look at past practices of conserving food. These practices were very much successful in the past.