Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
several dead moths, probably native agrotine noctuids, were found. Nonnative species recorded
during the survey included the millipede Oxidus gracilis, Rhopalosiphoninus latysiphon aphids,
Porcellio isopods, and shells of the garlic snail Oxychilus alliarius. Furthermore, dung of the black
rat (Rattus rattus) was found in the entrances; these animals can navigate through dark cave
passages.
The cave system skylights in the KFU support a variety of diverse native flora including „ākala,
Pipturus, Phyllostegia, Cyrtandra, Ilex, Cyanea, Metrosideros roots, and a variety of ferns (Howarth
and Stone 1998). The endangered Cyanea stictophylla previously occurred in a cave at the KFU;
however, it was destroyed by rat predation. The native plant „ōlapa is also known to occur in and
around the caves at the unit. Cattle often eat „ōlapa growing from the caves (Ball, pers. comm.).
Paleo-ornithological surveys by the Smithsonian Institute have found hundreds of subfossil bird
bones (geese and rails) in the KFU caves. Most of these species are extinct, while some are
considered new to science (USFWS 2008). Howarth and Stone (1998) found roughly 15 flightless
goose skeletons, as well as additional bird skeletons during their reconnaissance survey. None of the
caves surveyed by Raymond and Valentine (2007) in the KFU contain artifacts or other cultural
material.
Cave resources can be drastically altered by physical and biological changes or disturbance over the
surface. Toxins or pollutants on the surface can affect the subterranean ecosystem (Howarth and
Stone 1998). The input of soil and debris restrict water and nutrients from reaching deeper voids.
Herbivore grazing, mining, and chemical pollution are also threats to the subterranean ecosystems
(Howarth et al. 2007).
Nonnative species can alter the native ecosystem and adversely impact native species (e.g., through
predation). Nonnative taxa especially impact host specific animals, such as cixiid planthoppers, that
only utilize a single native species. People can directly impact cave resources by trampling
vegetation during exploration and management activities or through deliberate vandalism. Human
activity can also indirectly impact the ecosystem by inadvertently creating pathways for nonnative
species to invade the habitat (Howarth and Stone 1998).
At the KFU, staff minimize research and trespassing in the caves because heavy foot traffic increases
routes for pigs and other ungulates (Ball, pers. comm.). Any future surveys of the caves at the KFU
should be done with care to ensure as little damage as possible to the cave walls and floor (Howarth
and Stone 1998). Above ground management techniques to help protect these resources include
creating protected reserves around significant caves, controlling invasive plant species, and
encouraging the recovery of deep-rooted native species (Howarth et al. 2007).
4.12 Threats
Most of the habitats of the Hawaiian Islands have been drastically altered by humans, with less than
40 percent of native habitats remaining in the State (most of which are on the Island of Hawai„i). The
first Polynesians to arrive are believed to have brought coconut, taro, and Polynesian pigs. Europeans
arrived later and brought sheep, cattle, goats, and game birds. Before human arrival, the estimated
rate of successful new colonizations was 1 species every 25,000 years. Over the last 2 centuries
alone, the rate of plant introductions alone has been more than 40 species per year. It is estimated that
over 6,000 introduced terrestrial and aquatic species are now established, and that of all the species
4-82 Chapter 4. Refuge Biology and Habitats