Introduction

Oahu, Hawaii, USA. (Photograph by David Olson)

Tropical moist forests of Hawai'i are comprised of mixed mesic forests (about 750-1,250 meters (m) elevation), rain forests (found above mixed mesic forests up to 1,700 m), wet shrublands, and bogs in swampy areas. Moist to wet forests are commonly found on the windward lowland and montane areas of the larger islands and on mountain tops of some of the smaller islands. Koa (Acacia spp.) and ‘Ohi’a lehua (Metrosideros spp.) are common dominant canopy tree species.

Biological Distinctiveness

Tree snail (Achatinella mustelina), Hawaii, USA. (Photograph by WWF)

Mesic forests are the richest for many taxa and have the highest proportion of endemic tree species. Many of the honeycreepers, an endemic group of birds that displays many specialized adaptations to different food and plant resources, were found in mesic and wet forests. Hawaiian moist forest is the main habitat for other forest birds including the Hawaiian hawk, Hawaiian crow, Hawaiian honeyeaters (now extinct), and Hawaiian thrushes. This ecoregion was the center for adaptive radiation in honeycreepers, many plant species, Hawaiian Drosophila, and other invertebrates. These forests are also noted for the diverse assemblage of shrubs and trees that were found within the Koa and ‘Ohi’a forests. Rain forests, which occur in montane areas with high rainfall, are largely dominated by the tree Metrosideros polymorpha, with other wet forest tree species commonly present (e.g., Cheirodendron, Ilex, Antidesma, Melicope, Syzygium, Myrsine, Psychotria, Tetraplasandra, etc.), and tree ferns (Cibotium spp.) and a variety of shrubs and epiphytic plants covering the forest floor and tree surfaces. Clermontia, Cyanea, Gunnera, Labordia, Broussaisia, Vaccinium, Phyllostegia, and Peperomia are some typical plant genera. Numerous ferns and mosses as well as Hawaii's three native orchids occur in the rain forest. Bogs occur on montane plateaus or depressions and consist of a variety of sedges, grasses, ferns, mosses, small trees and shrubs that form irregular hummocks.

Conservation Status

Ohia lehua, Oahu, Hawaii, USA. (Photograph by David Olson)

Habitat Loss

Lowland and foothill moist forests have been largely eliminated. Some relatively large blocks of montane forest still exist on the larger islands, but even here there is much degradation from feral ungulates, introduced weed species, development, and recreational activities.

Remaining Blocks of Intact Habitat

Several important areas of relatively intact tropical moist forests currently have incomplete protection, including:

• Wai'anae Mountains of O'ahu
• East Moloka'i Mountains, West Maui Mountains
• Windward East Maui
• Lana'ihale of Lana'i
• the Kohala Mountains
• Hamakua-Hilo subregion
• Kona subregion of Hawai'i

Types and Severity of Threats

As stated above, recreation activities, including trampling by hikers, and the rooting of feral pigs, seriously threatens remaining Hawaiian bogs and wet forests. Introduced weed species and other non-native species threaten native flora.

Suite of Priority Activities to Enhance Biodiversity Conservation

• Control of feral animals and alien plants at Kauai Summit
• Establish protected areas and control alien species in the Koulau block
• Control alien species and continue efforts of TNC preserves in the East Molokai block
• Continue efforts of East Maui Watershed Partnership for control and monitoring of pigs and weeds in the East Maui watershed
• Control alien species in the West Maui block
• Continue efforts of NARs, Hakalau NWR, and Havo National Park in Windward Hawaii
• Establish protected areas and engage in feral animal and weed control in the Ka’u, Hawaii block
• Enhance NARS management and establish protected sites in central and north Kona and Hawaii blocks

Additional information on this ecoregion

• For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
• To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
• World Wildlife Fund Homepage