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Hawaiian High Islands Ecoregion
This page last revised 21 July 2007 

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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.

Worlds wettest regionsSome of the world's wettest regions lie in the ecoregion's montane systems

Ecoregion Description

Location and context

TheHawaiian High Islands Ecoregion lies in the north central Pacific Ocean. It is comprised of theecological systems, natural communities, and species associated with the terrestrialportion of the main archipelago of the Hawaiian Islands (eight major islandsand immediately surrounding islets). These islands have a total land area of 1,664,100hectares (4,062,660 acres). This terrestrial ecoregion excludes the Northwestern Hawaiian Islands(belonging to Hawai‘i coastal/marine ecoregion) and the surrounding marine environment.  The Hawaiian High Islands Ecoregion lieswithin the Hawaiian Biogeographic Province, which encompasses allof the above ecoregions and occupies the northern portion of the OceanianRealm.

Boundary

TheHawaiian High Islands Ecoregion Boundary is defined by the TNC/NatureServe National Ecoregional Map. It is a modification of Bailey's Ecoregions of the United States. The World Wildlife Federation (WWF) recognizes four ecoregionsfor the Hawaiian Islands(Hawai‘i Tropical Moist Forest [OC0106], Hawai‘i Tropical Dry Forest [OC0202], Hawai‘iTropical High Shrubland [OC0701], and Hawai‘i Tropical Lowland Shrubland[OC0702]) (Gon & Olson 1999, Ricketts et al 1998).

The Hawaiian HighIslands Ecoregion contains three major habitat types:
Tropical Moist Broadleaf Forest, Tropical Dry Broadleaf Forest, and TropicalGrasslands, Savannas & Shrublands.  Theboundaries of the Hawaiian High Islands Ecoregion correspond to the collectivesea-level island boundaries of the main Hawaiian Islands and immediatelysurrounding islets. There are no contiguous terrestrial ecoregions.

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physiography
The Hawaiian ecoregion contains highly diverse physiography.

Physiography

TheHawaiian High Islands Ecoregion is marked by a very wide range of localphysiographic settings. These include fresh massive volcanic shields andcinderlands reaching over 4000 m (13,000 ft) elevation; eroded, facetedtopo- graphies on older islands; high sea cliffs (ca 900 m [3,000 ft] in height);raised coral plains; and amphitheater-headed valley/ridge systems withalluvial/colluvial bottoms. Numerous freshwater stream systems are foundprimarily on the older, eroded islands, but also on the wet, windward slopes of even the youngest island, Hawai‘i (Juvik & Juvik 1998).

Climate

The general climate is tropical/subtropical, butwith combinations of elevation and orographic rainfall patterns that yield extremelywet (>1000 cm [>400 inches] annual rainfall) to extremely dry (<25cm [<10inches] annual rainfall) settings within a short distance of each other (<40km [25 miles]), topped by alpine deserts on the youngest and highest islands(Giambelluca & Schroeder 1998).All but two of the eight main Hawaiian Islands rise to montaneelevations (>1000 m [>3000 ft]). The general patterns of climaticvariationfound on the largest of the Hawaiian islands are shown diagrammatically below:
.

The Hawaiian High Islands Ecoregion (right, yellow oval) lies withinthe Hawaiian Province (red oval), in the Oceanian BiogeographicRealm. 
The global setting High island climatic setting

High islandorographic climate results in both extremes of wet and dry, while broadelevational reach yields tropical hot to alpine temperature regimes.(Click on the image above to view a larger version).
‘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.

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

Biodiversity Significance

The Hawaiian High Islands Ecoregion is marked by extremely high endemism (e.g.,~90% endemism of native flowering plants; >98% endemism of nativeterrestrial invertebrates) (Loope 1999). An estimated 15,000 endemic species occur in the ecoregion (Eldredge & Evenhuis 2003).  TheHawaiian floraof about 1,200 vascular plant species is disharmonic, that is, lackingmany genera and families that typically mark tropical island systems (Sohmer & Gon 1995). Rare and endangered taxa, includingendangered plants, forest birds, and land snails comprise >25% of the fauna. Hawai‘iincludes more endangered species than any other state in the U.S. (USFWS 2005). WWF includes the Hawaiian Islands as the site of four of their"Global 200" priority ecoregions (Olson & Dinerstein 1998).

In addition to species, all but ahandful of the approximately 150 described terrestrial native naturalcommunities are endemic. Vegetation includes grasslands, shrublands, woodlands,and forests in lowland, submontane, montane, subalpine, and alpine settings(Pratt & Gon 1998).  Hawai‘i supportsmore Holdridge life form categories than any other ecoregion known (Tosi et al2001, Ewell 2004). Lists of the natural communities and rare/endangered species of the ecoregion can be found in the appendices.


Endemism

Biological diversity in the Hawaiian Islands is spread among the main highislands because of island-level endemism. Each islandcontains species unique to that island. For example, of 1,050 described taxa ofnative flowering plants, there are three found only on Ni‘ihau, 225 restrictedto Kaua‘i, 157 found only on O‘ahu, 40 known only from Moloka‘i, 12 unique toLāna‘i, 96 found only on Maui, 2 reported only from Kaho‘olawe, and 106 knownonly from Hawai‘i (Wagner et al 1990).

Because of all of these island-levelendemics, fewer than half the flowering plant taxa (409) showmulti-island dis­tri­bu­tions. Fewer than 150 can be foundon allsix of thehigher main islands. The situation is even more pro­nounced amonginvertebrates,which comprise the majority of species-level diversity, and showremarkablediversification and geo­graphic endemism even within a singleisland setting.

Multiple examples of ecological systems acrossthe ar­chi­pelago are clearly required to ade­quate­ly represent species levelbiological diversity. For broad-scale planning, a geographic stratification approach is needed, and was developed as part of this 2nd interation plan.


land use
Significant portions of the lowlands have been dispolaced 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

Hula dancer in lei of native plants
Strong connections between the natural world and indigenous Hawaiian culture can aid conservation. 

Land Use Patterns

Humanresidence and extractive land uses are largely concentrated below 600 m(2000feet) elevation. Land uses include high-density urban, residential,agricultural, grazing, and lands dedicated to military training. Higherelevation areas are more natural, are largely zoned for conservation,andinclude many areas in protective status such as national parks, naturalareareserves, forest reserves, preserves, and refuges. Upland watersheds onmost ofthe main islands are included in informal public-private cooperativemanagementareas called watershed partnerships, managed for maintenance andmanagement offorested watershed. Over 30% of the ecoregion is privately-owned, 29%in state holdings,approximately 8% in federal lands, and the remainder in county andother tenure. These proportions also apply to the biologically intactislandinteriors, necessitating state, federal, and private participation incomprehensive conservation efforts (Hawai‘i GAP 2005).

The consequences of past land use practices canbe seen on Maui island(figure below). Anthropogenic and alien-dominated regions, shown in pink,dominate the lowlands, while native-dominated ecological systems prevail athigher elevations. Typically there is little or no native vegetation below 600m (2000 feet) elevation. In mesic settings suitable for grazing, thedestruction of forest and replacement by alien grasslands extends to thesubalpine zone (e.g., on the upper western flank of East Mauibelow).

Land use patterns on Maui
Remaining native-dominated regions on the Island of Maui (discussion above)


Continue to Ecoregional Conservation Targets

Socioeconomic Setting

The general setting for conservation in Hawai‘i is relatively stable. There isnone of the sometimes violent instability that plagues many tropicalbiodiversity hotspots. Hawaii's economy is marked bylow unemployment, and is largely based on tertiary services related to tourism.The military also plays a large economic role, as Hawai‘i has been a strategichub since World War II. Plantation agriculture (sugar andpineapple) was the primary economy in the early 20th century, but hasbeen declining in importance. 

Largetracts of former agricultural lands are being converted into residential areasor are left fallow, often creating vectors for weed invasions or wildfire. Rapidlyrising land and property costs (among the highest in the U.S.) havecreated a high cost of living, exacerbated by our geographic isolation and needto import many/most necessities (food, shelter, clothing, fuel). Economicallydepressed rural areas occur on all islands where subsistence hunting/fishingpersists. Business centers can be found in Honolulu (O‘ahu), Kahului (Maui), Līhu‘e (Kaua‘i), Hilo and Kailua-Kona(Hawai‘i). Societal stratification includes everythingfrom the very rich to the working poor, with a growing gap between the two.

Socio-economicimpacts on natural systems can be seen in urban and suburban sprawl thatimpinges on the boundaries of the Conservation District, continueddeforestation in agriculturally-zoned lands on the Island of Hawai‘i in theKona District, and damage inflicted by military training exercises in andadjacent to native ecological systems (especially on O‘ahu and Hawai‘iislands). Hawai‘i has largely effective land use zoning,establishing a Conservation District that corresponds well to the remainingnative-dominated areas (with some notable exceptions). 

Government agencies and the public recognize that natural areas and watershedsare important for quality of life. Strong connections between the natural world and indigenous Hawaiian culturehold great potential for conservation. However, conservation andpublic land management areseverely under funded and a multiple use mandate conflictswith management actions focused on biodiversity conservation. Highlandcosts make acquisition a very expensive strategy, and overall highcosts ofliving apply to the costs of essential management actions.