'Ewa Plains 'Akoko

Chamaesyce skottsbergii var. kalaeloana

Description

'Ewa Plains 'akoko is a small shrub with sturdy fibrous roots and woody stems with swollen nodes and large buds. Bark is smooth and light gray in color. Opposite, strongly oval leaves are dark green with prominent light green veins. Shrubs grow to a height of 24 in (60 cm) or more.

The cycle of flowering, fruiting and leaf fall is highly dependent upon rainfall. Germination occurs two to four weeks after the first winter "kona" storm in December or January. Leaf, bud, and floral production continues rapidly for four or five weeks, followed by heavy flowering. In years of normally heavy rainfall, the flower period extends for three months. (Cultivated plants will fruit year-round if continually watered.) When rainfall ceases, all the leaves fall and the plant becomes dormant.

Habitat

This species is adapted to the semi-arid conditions of a low coastal plain, built up from layers of coral. This type of coastal plain is characterized by some of the same features as limestone karst regions—sinkholes, irregular ridges, and massive rock outcrops. The plain, which lies at the base of the Koolau Mountains, receives less than 20 in (50 cm) of annual rainfall.

The continued disturbance of the habitat has allowed introduced plants to invade and displace native vegetation. Only small pockets of undisturbed habitat remain.

Distribution

Endemic to Oahu, this shrub was once more widespread on the 'Ewa Plains along the southwestern coast of the island.

'Akoko is now restricted to a single site near Barbers Point in the Naval munitions storage area. A 1981 survey located nearly 5,000 plants at this site, a figure that has remained stable.

Threats

The 'Ewa Plains have suffered from a wide range of human disturbances, beginning with the Polynesian settlement of the islands many centuries ago. Agriculture first claimed arable tracts of the plains. Later, land was pressed into use for various large-scale developments.

Many plants were lost to a coral quarry that was mined in the center of the largest, most concentrated population. When the harbor was dredged, plants occurring on the north side of the quarry were lost. Attempts were made to remove the plants in harm's way, but the adult plants were so firmly rooted that transplantation was not possible.

Although the 'Ewa plains 'akoko is threatened primarily because of habitat loss, it is also susceptible to competition by weeds and a parasitic vine that dominate the habitat. Insect infestations by the croton moth caterpillar denude the plant of leaves, flowers, and fruit within a few days. Heavy infestations of spiraling whitefly during drier months caused plants to die back.

Nearly 90% of the of the original acreage of the plains is currently used for a sugar plantation, an industrial park, and the Barbers Naval Air Station.

Conservation and Recovery

Threats posed by construction of the Barbers Point Deep Draft Harbor, a proposed federal and state project of massive proportions, triggered the federal listing of 'Ewa Plains 'akoko in 1982. Long before the listing was final, however, the U. S. Army Corps of Engineers, which was responsible for the harbor project, began consulting with the U. S. Fish and Wildlife Service (FWS) to head off what was shaping up to become a major conflict between the developers and the conservationists. Redesign of the port facility in its early stages, together with the discovery of a sizable new population of the 'akoko, relieved much of the immediate danger to the plant. Ultimately, only about 50 plants were lost to the construction of port facilities, a loss that was more than recouped through recovery efforts aimed at the surviving plants.

The munitions storage site is being managed to protect the plant population. The Corps of Engineers has funded further surveys and is supporting ongoing research into the plant's biology. The Navy, the Corps, and FWS are cooperating in transplantation experiments to expand the rather limited distribution of the 'akoko population. In the absence of further, unforeseen difficulties, 'akoko will probably thrive on these protected federal lands.

Contacts

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232
http://pacific.fws.gov/

U.S. Fish and Wildlife Service
Pacific Remote Islands Ecological Services Field Office
P. O. Box 50088
Honolulu, Hawaii 96850-5000
Telephone: (808) 541-1201
Fax: (808) 541-1216

References

Kurrus, T. 1985. "Uncle Sam in Paradise." Aloha 8(2):48-55.

Stone, C. P., and J. M. Scott, eds. Hawaii's Terrestrial Ecosystem: Preservation and Management. University of Hawaii Press, Honolulu.

Tabata, R. S. 1980. "The Native Coastal Plants of Oahu, Hawaii." Newsletter of the Hawaiian Botanical Society 19:2-44.

U.S. Fish and Wildlife Service. 1982. "Determination that Euphorbia skottsbergii var. kalaeloana ('Ewa Plains 'akoko) is an Endangered Species." Federal Register 47(164):36846-36849.