U.S. Department of the Interior USGS FS 2006-3035

U.S. Geological Survey March 2006

Background

The powerful volcanoes that formed the high islands of 

the Hawaiian archipelago block northeasterly tradewinds, 

creating wet, windward rain forests and much drier, leeward 

forests. Dryland forests in Hawai‘i receive only about 20 inches of rain 

a year. However, the trees in these forests intercept fog and increase 

ground moisture levels, thereby enabling these seemingly inhospitable 

habitats to support a diverse assemblage of plants and animals. 

Dryland forests of the Hawaiian Islands, like those worldwide, have 

been heavily impacted by humans both directly and indirectly. Less 

than 10% of Hawai‘i’s original dryland forest habitat remains. These 

forests have been severely impacted by urban development, ranching 

and agriculture, and invasive species. In particular, browsing animals 

and alien grasses have caused significant damage. Feral ungulates, 

including goats, sheep, cattle, and pigs, consume sensitive plants. Alien 

grasses have become dominant in the understory in many dryland 

habitats. In addition, these introduced grasses are fire-adapted and have 

increased the incidence of wildfire in these ecosystems. Native Hawaiian plants did not evolve with frequent fires or mammalian herbivores 

and typically do not survive well under these pressures. 

An Endangered Ecosystem on Maui

 On the east side of the Hawaiian Island of Maui, the dormant, but 

not yet extinct, Haleakalˉa volcano rises over 10,000 feet above sea 

level and that height, combined with the island’s size and age, created 

a large region of diverse dryland forest on its southern flank. Many 

biologists have considered these leeward Haleakalˉa forests to be the 

richest of Hawaiian terrestrial ecosystems. Unfortunately, the combined 

impacts of habitat destruction, ungulates, invasive plants, and wildland 

fires have reduced dryland forest to 5% of its original extent on Maui. 

An especially biologically diverse remnant of this forest type on 

leeward Haleakalˉa volcano is found in the Auwahi district, privately 

owned by ‘Ulupalakua Ranch. At Auwahi, much of the original native 

Restoration of Native Hawaiian Dryland Forest at Auwahi, Maui

A

Figure 1. Dryland forests in Hawai‘i harbor many species found nowhere 

else in the world. A. Maui ‘amakihi (Hemignathus virens wilsoni) on ‘ohia 

lehua (Metrosideros polymorpha, photo © J. Jeffrey); B. wiliwili (Erythrina sandwicensis, photo by J. Jacobi); C. the endangered Blackburn’s 

sphinx moth (Manduca blackburni, photo by B. Harrison Gagné). 

B

C

Maui

Auwahi Forest

The Main Hawaiian Islands

Figure 2. Maui is the second youngest and second largest island of 

the Hawaiian archipelago, positioned west of Hawai‘i island. Auwahi 

dryland forest is in the southern portion of east Maui island. Indicated in 

red, the study site is located along the southwest rift zone of Haleakal ̄a 

volcano. (Landsat images courtesy of NASA.)
shrub and fern understory has been replaced by alien kikuyu grass 

(Pennisetum clandestinum). This African grass forms a matted layer up 

to two feet thick that prevents the regeneration of native plants. Having 

lost many of the processes that keep a forest alive, Auwahi has become 

more like a museum than a forest. Just as in a museum, Auwahi is a 

place to observe isolated specimens of rare plant species, rather than 

a functioning forest. Although the ancient trees in this forest produce 

viable seed, few seedlings have become established in the last century.

The forest at Auwahi was well known to ancient Hawaiians because 

it harbored many useful plants. Of the 50 types of native trees at 

Auwahi, 19 were used for medicine, 13 for tool making, 13 for canoe 

building, and 13 for house building. Some plants had dual uses; species 

found at Auwahi also provided materials for making weapons, fishing 

implements and fish poisons, cordage and firewood, sticky substances 

for trapping birds for feather work, recreation, food, dyes and perfumes, and religious and cultural items. 

Restoration Techniques

In 1997, a partnership among visionary landowners, governmental 

resource managers and scientists was formed to explore methods for 

restoring this unique ecosystem before it was lost. Scientists from the 

USGS Pacific Island Ecosystems Research Center serve as scientific 

advisors and technical consultants to resource managers on the most 

efficient ways to achieve these goals. 

Prior to the experimental restoration of Auwahi forest, efforts to 

conserve dryland forests in Hawai‘i were focused primarily on the 

exclusion of ungulates and the removal of invasive plant species. 

Although these activities are important, they are not sufficient to reestablish self-sustaining native forests. In contrast, an important goal 

at Auwahi is to restore natural forest processes, such as seed dispersal, seed germination, and seedling regeneration. In recent decades, 

invasive plants and animals have destroyed those forest microhabitats 

that would allow natural seedling regeneration (cool, moist sites shaded 

by native shrubs and trees) at the site. The Auwahi restoration project 

encourages unassisted reproduction of long-quiescent forest species, 

once relegated as victims of a slow but inevitable extinction process.

Our approach to restoration includes three main elements: 1) high 

quality forest tracts are fenced to exclude ungulates, 2) volunteer and 

part-time laborers work to eliminate the kikuyu grass and other invasive species using both herbicides and hand-pulling, and 3) native tree, 

shrub, vine and grass species that were elements of the original forest 

community are outplanted during monthly volunteer trips. 

The first project undertaken at Auwahi was the construction of a 

four-hectare ungulate exclosure completed in 1997 (Figure 3). This 

exclosure has served as a prototype for subsequent restoration efforts. 

Within this exclosure, ungulates were eliminated, kikuyu grass mats 

were killed, and a program was initiated to augment numerous native 

plant species by broadcasting seeds and outplanting nursery-raised 

plants (Figure 4). 

Seeds collected from wild plants, particularly from rare and 

endangered species, are germinated and propagated at two nurseries. 

Every month, seedlings are outplanted by 20 to 40 dedicated volunteers 

(Figure 5). To date, over 300 community members have participated 

in these efforts and new people participate each month. As volunteers 

involve their friends and families, our volunteer community grows. 

Meaningful work gets accomplished on these 

trips, and perhaps even more importantly, 

Maui community members are exposed to 

the plight of native species and the positive 

role restoration can have in conservation. 

The impact of the real life environmental 

education being gained during these trips 

may be as significant as the actual restoration work being performed. 

Figure 3. A. Aerial image of 4 ha dryland forest exclosure at 1200m elevation at a site called Pu‘u-ouli in Auwahi. Outplanting of native shrubs and 

trees began here in 2000 and has proceeded to the point where nonnative grasses have been naturally excluded (Photo by A. Palomino). 

B. Native shrubs and trees are recovering inside the Auwahi exclosure. 

Protection from ungulates and establishment of favorable microhabitats 

inside the exclosure has encouraged natural unassisted reproduction of 

over 20 native species that mostly do not reproduce outside the exclosure. Some have not reproduced for many decades.

Figure 4. In the five years following completion of the four-hectare 

exclosure in 1997, dedicated volunteers have outplanted almost 1400 

plants inside the exclosure where they are protected from browsing 

ungulates. These activities have significantly increased the populations 

of many of these species. 

A

B

Scientific Name Status Wild Individuals 

on Maui

Outplanted 

at Auwahi

Population

Increase

Alectryon macrococcus

 var. auwahiensis

E 16 4 25%

Bidens micrantha kalealaha E 2000 200 10%

Melicope adscendens E 30 2 7%

Zanthoxylum hawaiiense E 6 50 833%

Santalum freycinetianum

 var. lanaiense

E 200 51 26%

Ochrosia haleakalae C 250 123 49%

Nothocestrum latifolium R 400 193 48%

Panicum tenuifolium S 350 95 27%

Pleomele auwahiensis S 1000 522 52%

Xylosma hawaiiense S 600 158 26%

E = endangered; C = candidate for protected status; R = rare; S = apparently secure
Native Species Increase in Managed Area

Unassisted natural establishment of seedlings and saplings of native 

shrub-tree species, such as ‘a‘ali‘i (Dodonaea viscosa), ‘ulei (Osteomeles anthyllidifolia), and pilo (Coprosma foliosa) is now common 

inside the exclosure. The increasing cover of these native shrub-tree 

species will likely make the site less susceptible to invasion by nonnative plant species and promote recruitment of native forest species. 

The creation of shaded microhabitats under these native shrubs has also 

enabled the regeneration of numerous rare and endangered species. 

After a single herbicide application, kikuyu grass in treated plots 

within the exclosure declined from 70% to less than 5% cover. The 

lack of subsequent kikuyu grass seedling establishment provides 

evidence of what ranchers believe, that local kikuyu grass does not 

produce seed. Although efforts to control kikuyu grass have been successful, one threat to the long-term conservation of Auwahi and similar 

forests is the spread of aggressive and shade-tolerant, non-native 

tree-shrub species, especially bocconia (Bocconia frutescens, Figure 6). 

Left uncontrolled, bocconia would likely become the dominant species 

at the site. 

The exclosure has provided a refugium for five endangered plant 

species, including: a‘e (Zanthoxylum hawaiiense, Figure 7A), two species of alani (Melicope knudsenii, seen in Figure 7B, and M. adscendens), mahoe (Alectryon macrococcus var. auwahiensis), ‘iliahi (Santalum freycinetianum var. lanaiense), and the endangered Blackburn’s 

sphinx moth (Manduca blackburni). 

Figure 5. A. Volunteers weeding and planting native seedlings in an 

Auwahi gulch, Fall 2000. B. By Fall 2004, native shrubs were the dominant 

vegetation component in the gulch.

Figure 6. The non-native tree bocconia is an ever-present challenge to 

dryland restoration because it produces millions of seeds that are dispersed by many introduced birds and that form a persistent seed bank. 

(Photos by F & K Starr) 

A

Figure 7. A. Less than a half dozen mature individuals of the rare and 

ethnobotanically important a‘e tree exist on Maui, most in the Auwahi 

district. Since 2001, in an attempt to rescue the nearly extinct Maui 

genotype, over fifty seedlings have been grown and outplanted in pollinating proximity of each other. B. There is a single surviving mature 

individual of alani (Melicope knudsenii) in the Auwahi district. This 

previously common endemic species, known only from Maui and Kaua‘i, 

is now limited to this one wild individual and one in cultivation at the 

D.T. Fleming Arboretum at Pu‘u Mahoe. Developing fruits are bagged to 

prevent near total loss of seeds caused by seed predation by the larvae 

of an endemic moth species. In 2005, eight seedlings were outplanted 

surrounding the last adult tree and are now growing vigorously. 

A B

B
For additional information 

please contact:

Art Medeiros, Research Biologist

Phone: (808) 572-4470

Email: amedeiros@usgs.gov

Fact sheet written by: 

Arthur C. Medeiros, USGS Pacific Island Ecosystems 

Research Center, and Erica vonAllmen, Hawai’i Cooperative Studies Unit

Photo Credits:

All photos taken by authors, unless otherwise noted.

Recommended Reading

Abbott, I.A. 1992. La‘au Hawai‘i: Traditional Hawaiian Uses of 

Plants. Bishop Museum Press, Honolulu, Hawaii, 163 pp.

Allen, W. 2000. Restoring Hawaii’s dry forests: research on Kona 

slope shows promise for native ecosystem recovery. Bioscience

50(12): 1037–1041.

Cabin, R.J. et al. 2004. Restoration of tropical dry forests in Hawaii: 

Can scientific research, habitat restoration and educational 

outreach happily coexist within a small private preserve? 

Proceedings of the 16th International Conference of the Society 

for Ecological Restoration, August 24–26, Victoria, Canada.

Medeiros, A.C., C. Davenport, and C.G. Chimera. 1998. Auwahi: 

ethnobotany of a dryland forest. Coop. Natl. Park Resources 

Studies Unit, Univ. Hawaii/Manoa, Dept. Botany. Tech. Rept. 117.

Lessons for the Future

We predict that native shrubs and trees will increasingly dominate 

the exclosure over the next decade, re-creating shaded understory sites 

probably similar to those of the original forest stands. Only time will 

tell whether the return of favorable microsites will spur the spontaneous reproduction of a broader spectrum of native dryland forest tree 

species, many of which have failed to reproduce naturally for decades, 

or whether some other perturbation will interfere.

Dryland forest on Maui constitutes a small but significant part of 

our nation’s natural heritage. Until recently, this ecosystem was believed to be impossible to restore and destined for extinction. With 

multi-agency cooperation, critical information and technology has been 

generated that promises to shift the trajectory of this ecosystem toward 

recovery and long-term conservation.

Both the restoration technology and the public-private partnership 

developed at Auwahi should serve as models for cost-effective, landscape-level restoration of leeward forest ecosystems across the Hawaiian archipelago. It is the hope of USGS scientists that Auwahi will 

serve as an important demonstration project for the restoration of 

ungulate- and fire-degraded ecosystems elsewhere in the Pacific Basin. 

Volunteers have been a key component of the restoration of the Auwahi 

dryland forest.

Auwahi Dryland Forest Restoration Partnership 

The community-based restoration of diverse tracts of dryland 

forest at Auwahi has been a surprising success thanks to the collaborative efforts of a visionary landowner at ‘Ulupalakua Ranch, 

state and federal agencies, and non-governmental organizations. 

These include: 

Federal agencies: 

USGS Pacific Island Ecosystems Research Center

USDA Natural Resources Conservation Service

Haleakalˉa National Park

US Fish and Wildlife Service

State and county agencies: 

State of Hawai‘i Division of Forestry and Wildlife

County of Maui Water Department

Non-governmental organizations: 

Community Work Day Program

D.T. Fleming Arboretum

Friends of Haleakalˉa National Park

Hana High School

Ho‘olawa Farms

Living Indigenous Forest 

Ecosystems

Lyon Arboretum

Maui Community College

Maui Nui Botanical Garden

Na Pua No‘eau

Native Hawaiian Plant Society

Rene Sylva

Private landowners: 

‘Ulupalakua Ranch Figure 8. Ochrosia haleakalae seedling 

(above) and flower (below left; 

photos by F & K Starr).