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Hawaiian High Islands Ecoregion
This page last revised 21 July 2007 

Conservation Targets
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Maps & Figures
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Hawaiian Islands from space
The Hawaiian High Islands Ecoregion lies in the central north Pacific Ocean.

Functional landscapes
Remarkable physiographic and climatic diversity marks the ecoregion.

Major Habitat Types


Major Habitat Types (MHT) are broad, typically large-scale aggregations of ecoregions of similar moisture, physiognomy, and latitude. Example MHTs include Temperate Conifer Forest, Boreal Forest/Taiga, and Tropical Moist Forest. Most ecoregions fall within a single MHT. However, the Hawaiian High Islands Ecoregion contains three major habitat types: Tropical Moist Broadleaf Forest, Tropical Dry Broadleaf Forest, and Tropical Grasslands, Savannas & Shrublands.  The Hawaiian High Islands comprise a significant representation of these MHTs within the Oceanian Realm, with Fiji, Samoa, and the Society Islands also contributing significant occurrences.


The MHT boundaries for the Hawaiian ecoregion are depicted below. The World Wildlife Federation (WWF) recognizes four ecoregions for the Hawaiian Islands (Hawai‘i Tropical Moist Forest [OC0106], Hawai‘i Tropical Dry Forest [OC0202], Hawai‘i Tropical High Shrubland [OC0701], and Hawai‘i Tropical Lowland Shrubland [OC0702]) (Gon & Olson 1999, Ricketts et al 1998). The last two shrubland types are combined into a single MHT (Tropical Grasslands, Savannas & Shrublands), while the moist and dry forest WWF ecoregions represent the other two MHTs (Tropical Moist Broadleaf Forest and Tropical Dry Broadleaf Forest).

(continued next column)
ecological amplitude
The Hawaiian ecoregion contains three Major Habitat Types.

Ecological System targets of the Hawaiian Ecoregion nest cleanly within the MHTs. For example, The Tropical Moist Forest MHT in Hawai‘i is comprised of five ecological systems: Lowland Wet, Lowland Mesic, Montane Wet, Montane Mesic, and Wet Cliffs.Similar nesting can be performed for the Tropical Dry Forest MHT andthe Tropical Grasslands, Savannas & Shrublands MHT.The integration of ecological systems into MHTs allows for ahigh degreeof accuracy reporting on their conservation status (see Global Priorites, below).

Global Priorities

The goal of The Nature Conservancy is to bring effective conservation to at least 10% of all of the Earth's Major Habitat Types by 2015. This 2015 goal is further stratified by biogeographic realms. The global context of the Hawaiian Ecoregion's three MHTs is the Oceanian Realm.
Because of its large size (relative to other Pacific island systems)and a long history of conservation efforts in the Hawaiian Islands,this ecoregion plays a significant role in realizing 2015 goals. 

Worlds wettest regionsSome of the world's wettest regions lie in the ecoregion's montane wet systems, part of the Tropical Moist Forest MHT.

The three Major Habitat Types (MHTs) of the Hawaiian High Islands Ecoregion (right) are comprised of constituent ecological systems and represent Tropical Moist Forest (green), Tropical Dry Forest (brown) and Tropical Grassland, Savanna & Shrubland (yellow). Areas that have been coverted into non-native or anthropogenic systems are shown in grey.

When comparing the current extent (top) of the MHTs to the prehumanextent  (bottom), it is apparent that all MHTs have beensignificantly reduced in extent, particularly at lowerelevations. Tropical Dry Forest has been all but lost except onthe largest island of Hawai‘i. Similarly, nearly all of thelowland grasslands and shrublands have been lost, leaving onlysubalpine and alpine shrublands
(yellow areas at the mountain tops of Maui and Hawai‘i) as the major representative of the Tropical Grassland, Savanna & Shrubland MHT.

The individual islands and their prehuman and current MHT occurrences are displayed and discussed in more detail below.

‘I‘iwi, a native honeycreeper
Hawai‘i boasts the highest overall species and ecosystem endemism of any ecoregion.

Rare natural community
The flora is disharmonic, lacking many of the typical tropical genera and families.

The patterns of MHT loss on the individual islands (right two columns)demonstrates clearly that disturbance and displacement of biodiversityhas been greatest in the lowlands, leaving remnant native areas athigher elevations.  As a result, smaller, lower islands such asMoloka‘i, O‘ahu, and Kaua‘i, show almost completeloss of the Tropical Dry Forest and Tropical
Grassland, Savanna & Shrubland MHT, but retain significant area of Tropical Moist Forest.

Endangered Achatinella tree snail
Hawai‘i includes more endangered species than any other state of the U.S.

land use
Significant portions of the lowlands have been displaced by human development.

Remote area management
Bringing active management to priority land- scapes isthe overall goal.

feral ungulates
Alien species, such as feral ungulates, are a prevailing threat to native ecosystemsin Hawai‘i

The summary statistics for each of the three MHTs in the Hawaiianecoregion shows that about half of the native Tropical MoistForest has been lost, and that only a third of the Tropical DryForest area remains. The summary statistic for Tropical Grassland andShrubland is misleading in a way, because nearly all of the lowland drygrasslands and shrublands have been lost, but the vast majority of thehigh elevation grasslands and shrublands remain. Similarly, it is easyto see that for all but the two largest islands (Maui andHawai‘i), Tropical Dry Forest and Tropical Grassland andShrubland has been largely destroyed.

Summary Statistics:

Tropical Moist Forest
area before humans:  795,867 hectares (1,966,629 acres)
current area:  408,790 hectares (1,010,142 acres) 49% lost

Tropical Dry Forest
area before humans:  507,520 hectares (1,254,110 acres)
current area:  172,653 hectares (426,634 acres) 66% lost

Tropical Grassland & Shrubland
area before humans: 363,299 hectares (897,731 acres)
current area: 212,933 hectares (526,170 acres) 41% lost