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The Watershed

Waterfalls in Waihe'e Valley (Photo: Chris Brosius)

A healthy watershed = clean water.  Damage from human activities and harmful introduced plants, insects, and large herbivores jeopardize the health of your watersheds.  How much is a healthy watershed worth to you?

Status of the West Maui Watershed

Data from 1999 shows that 70% of the land area of the Partnership is dominated by native vegetation.  That's good news.  However, perhaps less than 20% of this native landscape is without weed problems.

Feral animals, such as pigs, cattle, goats and Axis deer, help to spread weeds while they forage and wallow, displacing native plants and leaving huge areas primed for future invasion. Feral pigs have been seen directly, or their trails, wallows and rooting observed, on over 74% of the watershed, typically below about 3500 feet elevation.

Characteristics of the West Maui Watershed

The West Maui Watershed has horizontal bands of vegetation communities, arranged by elevation zone.  Ancient Hawaiians had long ago recognized these horizontal land divisions as having their own spiritual and practical purposes. 

OUR PRISTINE CORE:  Summit (5,788 ft.) to 2,800 ft.
This uppermost layer is the best of the best, the healthiest of our native forests, protected from grazing, browsing ungulates and the spread of weeds below by harsh terrain and strategic fences.  In this realm,  the dominant species is 'Ohi'a (Metrosideros polymorpha) and a diversity of native wet forest communities such as the montane bogs, wet cliffs, perennial streams, and wet windswept shrublands extend downward to more mesic forests and shrublands.  Other vegetation types include Koa (Acacia koa) forest, Lama (Diospyros sandwicensis) forest, diverse mesic forest (with several native tree species), and a variety of native shrubland types.

TRANSITION ZONE:  2,800 ft. to 2,000 ft.
In this mid-elevation band there is a mixture of native and invasive species.  This is the area where we would  like to continue restoration, gain better ground and hold it against alien invaders.  Below 2,800 feet elevation the vegetation transitions from native-dominated into more alien-dominated vegetation types, with non-native trees such as Strawberry guava (Psidium cattleianum),  Ironwood (Casuarina spp.), and others becoming increasingly prominent in a mixed native and alien canopy. Given enough time invasive species will gain more ground unless we are afforded the chance to do our work.


While this area may be dominated by alien plants, there are still pockets of rare individual plants and plant communities. Naturalized alien vegetation such as Guava forest (Psidium guajava and P. cattleianum) and Java plum (Syzygium cumini) dominate in this zone, with the exception of small native forest and shrubland stands.  At the bottom edge of the watershed, plantings of introduced trees such as Eucalyptus, Cook and Norfolk pines (Araucaria spp.), Silky oak (Grevillea robusta), and naturalized alien vegetation occupy the lowest slopes.