Acacia koa 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Fabales Fabaceae

Scientific Name: Acacia koa A.Gray
Common Name(s):
English Koa, Gray Koa
Taxonomic Notes: Acacia koa is very similar to Acacia koaia Hillebr. A. koaia has previously been assessed on the Red List (Bruegmann and Caraway 2003). For the purposes of this assessment A. koa Gray is treated as a separate species.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2012
Date Assessed: 2010-03-03
Assessor(s): Contu, S.
Reviewer(s): Hilton-Taylor, C.
Acacia koa is currently known to be the dominant canopy endemic tree occurring on six of the Hawaiian islands. The species occurs in mesic forest in a wide range of habitats and elevations (60-2,300 m), and is therefore currently rated as Least Concern. Due to the restricted distribution range and to the fact that processes, such as timber extraction or invasion of alien species, might cause a population decline, A. koa should be monitored over a longer period of time to make sure of the health and status of the populations, along with in situ conservation measures to ensure that the supopulations number and range do not decrease in the future.

Geographic Range [top]

Range Description:Acacia koa is endemic to the Hawaiian islands - Kauai, Oahu, Molokai, Lanai, Maui and Hawaii.
Countries occurrence:
United States (Hawaiian Is.)
Additional data:
Lower elevation limit (metres):60
Upper elevation limit (metres):2300
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:A. koa is known to be widespread within its range and often the dominant species.
Current Population Trend:Stable
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:A. koa is a large evergreen broadleaf tree (it can reach 35 m, but more commonly reaches 20-25 m in height, and some populations are much smaller, with a shrub-like form), which can grow in pure stands, but usually is found in mesic forest. Koa is found on all volcanic soil types of all geologic ages. It grows well in moderately to well-drained, medium to very strongly acid soils on both flatland and steep slopes. Occurs in a variety of habitats, has a large elevation range and is often a dominant plant in dry to wet forests at elevations ranging from 60 to 2,300 m (Wagner et al. 1990). Morphological differences in koa have been observed on several islands. Seeds are contained within a pod 15–20 cm long, containing 6–12 seeds. The species is a fast-growing tree.

Use and Trade [top]

Use and Trade: The species is mainly used for the timber (currently one of the most expensive woods in the world (Elevitch et al. 2006)), furniture, veneer, and crafts.

Threats [top]

Major Threat(s): A. koa forests were more extensive in the past but land clearing, destruction by animals (animals such as horses, cattle, goats, and pigs are also a very common source of high seedling losses and damage to trees less than 10 years old), insects (in some areas alien insects destroy almost all of the A. koa seeds), alien invasive plants and fire have all contributed to the reduction of its range. The species in the past could be found at 60 or 90 m of elevation, but pests and diseases currently limit koa’s optimal range to elevations above 610 m. On the other hand with long-lived seeds and the ability to regenerate after fire, koa may have potential as a problematic invasive species outside its native range. The species is used for timber, but at present there is not evidence of a population decline due to the species utilization; population dynamic study should be carried out to better understand the species trend.

Conservation Actions [top]

Conservation Actions: A. koa trees were planted on the islands (more than 1.3 million koa seedlings were planted by the Hawaii Division of Forestry and Wildlife between 1915 and 1946 for watershed protection; in the Hakalau Forest National Wildlife Refuge etc.), because it is an important endemic species for reforestation of degraded lands and is of critical ecological importance because it provides habitat for numerous endemic birds and insects. The abundance and distribution of the Akiapolaau (Hemignathus munroi; Endangered IUCN ver 3.1), Akepa (Loxops coccineus; Endangered IUCN ver 3.1), and Hawaiian Creeper (Oreomystis mana; Endangered IUCN ver 3.1), three of the endangered forest birds on the island of Hawaii, are strongly associated with Koa in forest communities. A. koa has been listed as Apparently Secure (G4) from NatureServe (2009), which is equivalent to IUCN category Least Concern (LC).

Citation: Contu, S. 2012. Acacia koa. The IUCN Red List of Threatened Species 2012: e.T19891713A19999145. . Downloaded on 20 May 2018.
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