Complex sentence: While the actions of the White-eye on the Hawaiian and Bonin Islands are indeed different, they are both significant, because islands themselves are particularly vulnerable to the drastic effects of introduced competitors, predators, and diseases when these communities have evolved in their absence.
Split into simpler sentences: While the actions of the White-eye on the Hawaiian and Bonin Islands are indeed different, they are both significant. This is because islands themselves are particularly vulnerable to the drastic effects of introduced competitors, predators, and diseases, because these communities have evolved in their absence.