Long-term rain forest succession and landscape change in Hawai'i: The 'Maui Forest Trouble' revisited

Because of their isolation and geographical position, and in contrast to the multi-species tree canopies of tropical rain forests on the continents, the Hawaiian Islands have only two native dominant canopy species in their rain forests, Acacia koa and Metrosideros polymorpha. The wetter forest ecosystems are dominated by only the latter. In 1905, a dieback of lowland tropical Metrosideros rain forest was observed over a 35 km stretch on the lower east slope of Haleakala Mountain on Maui Island. This was dubbed 'The Maui Forest Trouble.' Although the synchronous decline of so many trees was initially believed to be caused by an epidemic disease, a decade of research yielded no pathogen. The conclusion was that the Hawaiian flora consisted primarily of colonizer species that were unable to continue growing on aging soils. Although this made ecological sense at that time, it was a rather limited and thereby unfortunate conclusion. Further research has shown that the Maui Forest Trouble was a 'bog-formation dieback', a process of vegetation dynamics not only related to soil aging but more broadly to geomorphic aging and fundamental landscape change. This process is clearly a marginal-site syndrome, but a natural process of profound consequence for biological conservation. This will be further explained as a paradigm for vegetation ecology.