Introduction and Spread of Mangroves in the Hawaiian Islands

The terrestrial flora of Hawaii was derived from a small number of ancestral species as a result of the archipelago's remote location. Great expanses of open ocean separate Hawaii from continents and other islands, and thus water has acted as an effective barrier even to many widespread drift species whose propagules can float and withstand long immersion in seawater. The intertidal zone in Hawaii lacked vascular plants entirely despite the availability of habitats suitable for many of them (Guppy 1906, Egler 1942). The introduction and subsequent naturalization of mangroves and other exotic species has produced significant changes in the coastal environments. Mangroves are opportunist trees that colonize the tidal zone of tropical coasts. The most extensive stands occur on aggrading shores which receive sediments from large drainage systems, but small colonies also can be found on limestone coasts, coral atolls, sand beaches, and lagoons, suggesting that protection from wave action, rather than the presence of fine sediments, is a prerequisite for seedlings to take root (Sauer 1976).