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Restoring Native Forests in Hawaii:
The Role of Cooperative Extension

Restored 25 year old koa forest

J. B. Friday
Extension Forester
University of Hawaii
Cooperative Extension Service

Paper presented at the

International Union of Forestry Research Organizations'
6th Extension Working Party Symposium
Troutdale, Oregon, USA

September 28 to October 3, 2003


Hawaii has lost much of one of the few tropical forests in the United States to conversion for agriculture and has become the "endangered species capital" of the country. Remaining native forests face an onslaught of invasive alien weeds. Recently, galvanized by the knowledge of what stands to be lost and a new environmental ethic, private landowners as well as government agencies have been working to restore native Hawaiian forests. Restoration efforts have ranged from small gardens located in urban areas to hundreds of acres of former ranch lands. Some are aimed at restoration of as close to natural plant communities as possible, while others, particularly on private lands, consider possibilities of harvesting timber or non-timber forest products. Cooperative Extension's role includes applied research, technology transfer, and community education. On the applied research side, investigators from the University of Hawaii, the USDA Forest Service, the Nature Conservancy of Hawaii, and the private Hawaii Agriculture Research Center are applying silvicultural principles to management of Acacia koa, Hawaii's largest tree species and one of the world's premier tropical hardwoods. The research is hosted and supported by Kamehameha Schools, Hawaii's largest private landowner, and other private landowners have been well represented at project field days. Other projects include use of herbicides to control alien weeds in forests and natural areas, use of mycorrhizal inoculation for native plants, and the propagation of native Hawaiian species. A series of workshops on "Native Plants in Public Places" has educated arborists and landscape architects about possibilities in featuring Hawaii's native flora in urban settings rather than the more common exotics. In addition to conferences workshops, and field days, Cooperative Extension makes as much material as possible web-based to reach a wide audience spread out on different islands and across the Pacific.

A 27 year old koa tree

Aloalo, Hibiscus clayi, a native Hawaiian hibiscus

Ma'o hau hele, Hibiscus brackenridgei,
the state flower

Restoring, managing, and protecting native ecosystems has become the most important task for the forestry profession in Hawaii. Traditional land grant colleges have a unique strengths in combining research and outreach. Research and programs which have focused on traditional production agriculture for generations are now taking up new challenges in the much broader field of ecosystem management.

Dry alpine forests and snow on Mauna Loa

Akaka Falls

Hawaii is the most geographically isolated set of islands on the globe. Originating from a few pioneer species which drifted to Hawaii on the ocean currents, the wind, or the backs of migrating sea birds, the Hawaiian flora has evolved hundreds of unique native species. Of almost a thousand species of native flowering plants in Hawaii, almost 90% are endemic (Wagner, Herbst and Sohmer 1999). Diverse native forests exist in wet areas that receive over 6000 mm of annual rainfall, in dry areas that get only 500 mm, and in cool alpine areas of over 2500 m elevation. Some forests in leeward and coastal areas were cleared for agriculture by the original Polynesian settlers who arrived from the South Pacific around 300 CE (Juvik and Juvik 1998).
Much more damaging to native ecosystems was the arrival of Western settlement and agriculture in the 19th and 20th centuries. Vast areas of lowland forest were cleared for sugar cane and pineapple plantations, while upland areas were grazed by imported cattle, sheep, and goats.

Native forests cleared for development

Along with the loss of natural areas has come a wave of extinctions. Two hundred and seventy three plant species and 44 animal species are listed as threatened or endangered by the USDI Fish and Wildlife Service, including the state flower, ma'o hau hele or yellow hibiscus (Hibiscus brackenridgei) and the state bird, the nene goose (Branta sandvicensis).

Dryland forest above Kona

Fountain grass, an alien weed

The threat to Hawaiian forests today is less from outright clearing than from depredations of feral domestic animals and invasions of aggressive alien weeds. Wild cattle, sheep, and goats graze native vegetation in the mountains and feral pigs uproot and destroy rare native plants in wet forests and spread the seeds of weedy species. Hawaiian plants are particularly vulnerable to damage from feral animals because they evolved in the absence of large herbivores and in doing so lost most of their natural defenses. Hawaii forests include mints without mint, nettles without stings, greenbriar without thorns, and raspberry without prickles. The native plant ecosystems, composed of accidental introductions and locally evolved species, also are not resistant to invasions of aggressive alien weeds which are often faster growing, more shade tolerant, or dispersed more readily than native species. Many of the trees and plants introduced in the past for ornamental, agricultural, or forestry use have escaped and become serious pests of native ecosystems.

Plantation of tropical ash

Native forest invaded by alien kahili ginger

Pig damage on a native tree fern

Cow grazing in native forest

What is being done? Largely beginning in the 1990s, private landowners have undertaken protecting indigenous plants and restoration of native forests, on scales ranging from small urban gardens to tens of thousands of acres. In a recent needs assessment of clients of the University of Hawaii forestry extension program, information on native forest restoration came out at the top of the list. Currently there are several cost-share programs available for landowners who want to restore native forest, including some from the state of Hawaii Divison of Forestry and Wildlife, the USDA-funded Forest Legacy Enhancement Program (FLEP), the NRCS Environmental Quality and Wildlife Habitat programs, and the USDI Fish and Wildlife Conservation Partnerships program, and the state Kaulunani Urban Forestry program.

Ancient koa tree

One example of large-scale restoration is the koa reforestation program of Kamehemeha Schools' Keauhou Ranch. Kamehameha Schools is a private foundation dedicated to funding education for Hawaiian students. Their lands are used both for income generation and as outdoor classrooms for their students.Acacia koa is the largest tree in the Hawaiian forest and one of the most valuable timbers in the world. Currently koa stumpage ranges from $2000 to $3000 per mbf, and select koa lumber sells for $30 per board foot and up. The koa forest is the habitat for a number of endangered birds and plants. Koa wood has historically been undervalued, however, and large areas that were once koa forest were cleared for ranching in the past two centuries. At Keauhou Ranch, Kamehameha Schools began setting aside portions of the land for reforestation in the late 1970s. Koa regenerates prolifically from buried seed in old pastures after soil scarification, but little is known about how to manage the resulting dense stands (Grace 1995, Pearson and Vitousek 2001).

Thinning dense stands of koa

In a cooperative effort of the University of Hawaii, the USDA Forest Service Institute of Pacific Islands Forestry, and the Hawaii Agriculture Research Center, we are investigating whether middle-aged (25 year old) koa trees respond to thinning, fertilization, and release from weed competition. A similar project is being carried out by The Nature Conservancy and the Forest Service on the other side of the island. Our research plots have also served as demonstration sites for field days for other landowners around the state. Because the profitability of ranching, never great, has declined in recent years, private landowners around the state are looking into reforestation as a possible alterative land use. While most would like to grow native trees, they also require some promise of income from the land. If our thinning and fertilization trials are successful, the techniques developed could be applied to help reforest tens of thousands of acres of marginal ranch lands.
Through Kamehameha Schools, which is dedicated to Hawaiian students, and through the University's Hawaiian Internship Program, we are also working to get more native Hawaiians involved in professional conservation efforts. Currently hundreds of Hawaiian high school students participate Kamehameha Schools' reforestation efforts annually and college students work as interns on various research projects at Keauhou Ranch.

Koa seedling

Koa field day at Keauhou

Another area where the University is aiding in forest restoration is in the working out of techniques for mycorrhizal inoculation of native tree seedlings. Research has established that some major Hawaiian forest species such as the legumes koa and mamane (Sophora chrysophylla) are strongly mycorrhizal (Miyasaka et al. 1993), and inoculation seems to help trees get established quickly in degraded sites. Growers from both public and private nurseries have attended extension workshops on the use of mycorrhizal inoculants for growing native trees.
Techniques for mycorrhizal inoculation of seedlings developed at the University (Habte and Osorio 2001; Miyasaka et al. 2003) are being used by the Hakalau National Wildlife Refuge to restore native forests in former pastures on the Big Island of Hawaii and create new habitat for endangered birds.

Land grant colleges have traditionally worked on weed control for pastures and agricultural areas. In Hawaii, restoration of native ecosystems always entails combating alien weeds. Weed control techniques developed for range lands also serve well in restoring and maintaining natural areas (Motooka et al. 2002). Low-volume, high concentration applications of woody plant-specific herbicides have proven effective in controlling weedy tree species in wet forests. Timely application of grass-specific herbicides coupled with mechanical control has been effective in controlling alien grasses in dryland forests and thus reducing the risk of wildfires. Workers from state and federal land management agencies, along with those from private landowners such as The Nature Conservancy, have been eager participants in workshops on weed control. In the past year Cooperative Extension has published two books on methods of herbicidal weed control for natural areas and on weeds of natural areas and how to identify them (Motooka et al. 2003).

Workshop on control of fountain grass, Kona

Ko'oloa 'ula, Abutilon menziesii

While foresters and naturalists know about the unique biodiversity of the Hawaiian Islands, most people in Hawaii seldom if ever see native Hawaiian plants. Almost all ornamental plants used in the landscape trade are exotic, and one sees the same street trees in Honolulu as in Puerto Rico or Manila. A series of very popular workshops held by the Cooperative Extension Service and horticulturists from the University has focused on Native Plants in Public Places. The aim of the workshops was to introduce arborists and landscape designers to native Hawaiian plants and promote their use so that both local people and visitors begin to recognize and appreciate them.
People only value what they know, and public support for conservation and restoration programs hinges on people being aware of Hawaii's unique flora. Horticulturists with the UH Cooperative Extension Service and 4H programs have also been educating the public through creation of native plant gardens in urban areas.

A field day at the urban native plant garden in Liholiho Park, Hilo

Koki'o ke'o ke'o, Hibiscus arnottianus var. immaculatus

Loulu, Pritchardia martii, Kona

Ma'o, Hawaiian cotton

One of the difficulties nurseries and landscapers have faced in using native plants is the lack of standard, known propagation techniques. While a dozens of native species have been brought into cultivation, many of these require specialized techniques to germinate and culture. Extension leaflets on growing native plants have been written and are available to the public for purchase and on our website (Hollyer 2003; Bornhorst and Rauch 2003). A Native Plant Propagation Database summarizes research done by UH scientists and others on how to grow Hawaii's indigenous and endemic plants.

Nationwide, Cooperative Extension has seen its role expand from promoting production of timber and agricultural commodities to encompass stewardship of the environment. In Hawaii, the most important challenge in natural resources is protecting and restoring native ecosystems. Much of the knowledge and many of the methods traditionally used in agricultural and forestry science are also useful in practicing biological conservation. Most of the biologists who are responsible for managing conservation programs, however, come from pure research backgrounds rather than agriculture or forestry. Although their work often requires interacting with the public, they may not understand or value the role of research-based extension as exists in the land-grant system. Extension programs at land grant colleges have a lot to share.


(On-line reference require Adobe Acrobat Reader)

Bornhorst, HL and F Rauch. 2003. Native Hawaiian plants for landscaping, conservation, and reforestation. Ornamentals and Flowers series no. 30. College of Tropical Agriculture and Human Resources, University of Hawaii, Honolulu, HI.

Grace, KT. 1995. Analysis and Prediction of Growth, Grazing impacts, and Economic Production of Acacia koa. PhD dissertation, Department of Agronomy and Soil Science, University of Hawaii at Manoa, Honolulu, HI.

Habte, M, and NW Osorio. 2001. Arbuscular Mycorrhizas: Producing and Applying Arbuscular Mycorrhizal Inoculum. College of Tropical Agriculture and Human Resources, University of Hawaii, Honolulu, HI. (order blank)

Hollyer, J, ed. 2002. Growing Plants for Hawaiian Lei: 85 Plants for Gardens, Conservation, and Business. College of Tropical Agriculture and Human Resources, University of Hawaii, Honolulu, HI. (order blank)

Juvik, S. and J. Juvik, eds. 1998. Atlas of Hawaii, Third Ed. University of Hawaii Press, Honolulu, HI.

Miyasaka, SC, M Habte, JB Friday, and EV Johnson. 2003. Manual on arbuscular mycorrhizal fungus production and inoculation techniques. Soil and Crop Management series no. 5. College of Tropical Agriculture and Human Resources, University of Hawaii, Honolulu, HI.

Miyasaka, SC, M Habte, and DT Matsuyama. 1993. Mycorrhizal dependency of two Hawaiian endemic tree species. J. Plant Nutrition 16(7): 1339-1356.

Motooka, P, L Castro, D Nelson, G Nagai, and L Ching. 2003. Weeds of Hawaii’s Pastures and Natural Areas: An Identification and Management Guide. College of Tropical Agriculture and Human Resources, University of Hawaii, Honolulu, HI. (order blank)

Motooka, P, L Ching, and G Nagai. 2002. Herbicidal weed control methods for pastures and natural areas of Hawaii. Weed Control series no. 8. College of Tropical Agriculture and Human Resources, University of Hawaii, Honolulu, HI.

Pearson, HL and PM Vitousek. 2001. Stand dynamics, nitrogen accumulation, and symbiotic nitrogen fixation in regenerating stands of Acacia koa. Ecological Applications 11(5): 1381-1394.

Wagner, WL, DR Herbst, and S Soehmer 1999. Manual of the Flowering Plants of Hawaii, revised edition. University of Hawai'i Press, Honolulu, HI.

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Last updated on 8/23/2004