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Introduction and Background - The Value of Forested Watersheds Native Ecosystems - Primary Threats - Existing Management

The greatest current threat to the native forests and watersheds of the KWA lands is a combination of the destructive effects of non-native animals such as pigs, goats, cattle, and deer and invasive plants.  Non-native animals damage the vegetative structure, introduce diseases, and open the way, via groundcover disturbance for plant pests such as Strawberry guava, Clidemia, Melastoma, Australian tree fern, Miconia, and Kahili ginger. Native Hawaiian forests cannot withstand the effects of large land mammals.  The animals browsing, rooting, and trampling, destroy vegetation, accelerate erosion, pollute the water supply with silt, feces, and disease, and create disturbed areas in which weeds can establish and spread.  Some of these weeds have completely displaced diverse assemblages of native plants and replaced them with near monotypic stands.

Natural Resource Manager, Sarah Newton (left) applies herbicide to the growing tip of an Australian Tree Fern.

Kahili Ginger (right) is an extremely invasive understory weed and a first priority species for management.  Left untreated, this flowering clump (right photo) will continue to grow and spread, forming a monotypic stand that prevents recruitment of other plants.

An Australian Tree Fern infestation (left) is present on a hillside in Hanalei Valley.  ATF spores are wind dispersed allowing individuals to penetrate deep into the island's interior.

The showy flowers of kahili ginger forms fruits (right), which are eaten by birds who then distribute the seeds to new locations.

Two severe hurricanes in 1982 and 1992 caused widespread disturbance of native vegetation and accelerated the spread of established weeds over a large portion of the Kaua‘i watershed especially along its edges.  By disrupting access roads, hunter trails, and management programs, these hurricanes also caused feral animals to increase in number in some parts of the area that had previously been only lightly damaged. Hurricane damage will recur on Kaua‘i perhaps at greater frequency than on more southerly Hawaiian high islands.  We must expect that this will continue to set back native vegetation in some areas by encouraging gap-filling weeds.

Weeds and feral animals are well established in the watershed.

Strawberry guava is also well established on Kaua‘i and threatens to spread further into the Alaka‘i.  Guava forms dense monotypic stands which few plants can grow underneath.

One of the greatest weed threats, Miconia (left photo) threatens to spread into the watershed from an outbreak in the Wailua area.

Its relative Clidemia (Right and Left) is already well established in most of the island's forests and forms dense stands in the understory as well as in the open (right), crowding out desirable plants and forming thick patches that are difficult for hikers, hunters, and other outdoor users to pass through.

Pigs are found virtually throughout the island except on steep cliffs; goats are in many areas (including steep cliffs); and black-tail deer are present throughout the western half of Kauai.

A feral goat, within the vegetation on the Na Pali Coast.  Feral goat populations exist in the Waimea Canyon, Na Pali Coast, Makaleha Mountains, Ha‘upu Ridge, Na Pali Kona Forest Reserve, and Lumaha‘i Valley. Pigs are ubiquitous throughout Kaua‘i where they are highly valued as a source of food and recreation by the hunting community.  Intensive reduction of feral pigs is planned only for the most remote and inaccessible areas of Kaua‘i.  The picture, above and to the right, is a dead pig found in the ‘Ili‘ili‘ula Stream.

Other Threats Fire is a major threat to native resources in the western, drier portions of the watershed.  Lately, there has been an increase in human disturbances, including trespass and damage to watershed lands from uncontrolled recreational motorcycle riding, illegal collecting of plant material, illicit cultivation of marijuana, and unauthorized blazing and extension of hiking trails deep into the watershed.  These actions can be curtailed through increased education and outreach efforts.

Introduction and Background - The Value of Forested Watersheds Native Ecosystems - Primary Threats - Existing Management