The objectives of scientific research at the NTBG are to:
- Assess and document plant diversity through field surveys, collecting, and identification
- Contribute to, support, and undertake evaluations and assessments of threatened plants
- Prioritize regional conservation efforts for all plant life
- Identify and target important areas for plant diversity
- Establish methods for sustainable use of plant diversity
- Build capacity for conservation of plant diversity
- Share scientific knowledge and awareness of plant diversity through publications and education
In seeking to achieve these objectives, our research initiatives focus on systematics and taxonomy, floristics, restoration ecology, horticulture, ethnobotany, and even nutrition, with an emphasis on plants and habitats in Hawai‘i and the Pacific Islands overall.
Flora of the Marquesas Islands
The Marquesas Islands (French Polynesia) are of volcanic origin and are the world’s most remote archipelago. Humans, feral animals, and alien plants have severely impacted the lowland and mid-elevation vegetation. Steep and rugged, the Marquesas are critical to understanding Pacific island biogeography, but they have been poorly explored compared to the rest of French Polynesia and many other Pacific islands. Most importantly they lack a written flora, which is essential for providing a basic taxonomic framework and reliable botanical names. Currently the Marquesan vascular flora -- the ferns, fern allies, and flowering plants -- is estimated to comprise 360 species of which 45 percent are endemic or found nowhere else, including three endemic genera.
The Flora of the Marquesas Islands is a collaborative project between the National Tropical Botanical Garden, Smithsonian Institution, and Délégation à la Recherche (Tahiti, French Polynesia). Collecting expeditions have yielded nearly 6,000 herbarium specimens, comprising 714 vascular plant species and 61 new species. An Internet-based flora hosted by the Smithsonian Institution provides access to a database of specimens, plant images, checklists, island distributions, and literature. In addition to this Internet flora, a two-volume flora will be printed.
Hawaiian and Pacific Island Rubiaceae
The primarily tropical Rubiaceae, or coffee family, is the world’s fourth largest flowering plant family, with approximately 637 genera and 11,000 species. Various species produce alkaloids responsible for their economic and medicinal utility. Best known is coffee, the family’s most important commercial crop, derived from seeds of Coffea arabica cultivars. Other useful Rubiaceae include: Cinchona, whose bark is the source of quinine and other anti-malarial compounds that have saved millions of lives, and Psychotria ipecacuanha, whose roots yield ipecac syrup, used medicinally as an expectorant in cough syrups and as an emetic in cases of poisoning. Noni, or Indian mulberry (Morinda citrifolia), from Hawai‘i and other Pacific islands is widely used as a medicinal plant. A number of tropical genera such as Gardenia, Ixora and Mussaenda are widely cultivated for their ornamental and horticultural value.
Many Rubiaceae are poorly known and understudied in terms of their economic and horticultural potential. Through field collecting and exchange with other botanical gardens, an important research and conservation collection of Rubiaceae has been established at the NTBG. The over 400 accessions of Rubiaceae include numerous species from Pacific Islands, as well as rare or endangered Hawaiian species.
Restoration Ecology is the study of recovering degraded, damaged, or destroyed ecosystems. Restoration is essential for the preservation of species on the brink of destruction. Because this is the most effective method for ensuring the survival of endemic plant species, the NTBG has initiated restoration projects in its gardens on the island of Kaua‘i and its preserves on the island of Hawai‘i. In any restoration project a critical need is to understand the ecological history of the site. Information obtained from the fossil and archaeological records combined with the knowledge of traditional cultural practitioners and contemporary field botanists can provide important understanding about the original condition and subsequent changes to the habitat.
There are several restoration projects underway in the Lāwa‘i Valley. An innovative and strategically significant restoration project on the west slope of the valley is the Lāwa‘i Forest Restoration Project, which is recreating a dry-mesic forest ecosystem that has been all but eliminated on Kaua‘i by agriculture, livestock grazing, and real estate development. Re-creation of these plant communities will provide habitat for at least 100 native plant species, many of which are threatened or endangered.
The stream which runs through the McBryde Garden and the Allerton Garden is typical of streams found on volcanic islands throughout Oceania. The Lāwa‘i Stream Restoration Project is addressing stream flow and quality degradation that have accumulated over many years of agricultural and other uses of the watershed. The project includes removal of undesirable plant species, protecting and managing desirable existing vegetation, and restoration of the streambed to improve water flow.
At Lāwa‘i-kai, an ambitious restoration of the beach and adjacent coastal forest has involved removal of alien grasses from the beach strand and the creation of a stable habitat for a wide array of highly endangered endemic plants, as well as restoration of a nesting site for the threatened Hawaiian green turtle or honu. The multi-layered canopy of native and Polynesian plants, with a dense groundcover of native species, has served as an example and inspiration for many other projects, including those of other organizations and agencies.
NTBG is conducting restoration projects in both the lower and upper portions of the Limahuli Preserve. In the Lower Preserve, a multi-year project has resulted in the successful re-establishment of the native canopy; the newest initiative is restoring the native understory, which will produce an environment more conducive to the regeneration of native species. In the Upper Preserve we are augmenting populations of threatened and endangered species natives, while at the same time intensifying efforts to eradicate incipient invasive species in this largely pristine ecosystem.
Additional research is being conducted in one of NTBG’s other preserves, Ka’upulehu, located on the island of Hawai‘i. NTBG staff members and research associates are assessing the resulting impact of eliminating invasive weeds at the 8-acre site.
NTBG collaborates with government agencies and private landowners to expand its research and conservation initiatives. One project involves long-term monitoring and comparison of fenced versus unfenced plots to study the impact of feral ungulates, such as pigs and deer.
Breadfruit has been an important staple food crop in the Pacific for more than 3,000 years and was distributed throughout the Caribbean in the late 1700s. However, it has been underutilized in most tropical areas because of the limited distribution of varieties and the difficulty of importing viable plant material into other countries. The fruit is a good source of Vitamin A, fiber, and is comparable to or better than white rice as a source of calcium, magnesium, potassium, and thiamin.
NTBG’s Breadfruit Institute (BFI) is investigating the potential of breadfruit to address malnutrition and hunger in a number of tropical countries. A ten-year seasonality study was completed, using the comprehensive collection at Kahanu Garden, to determine which varieties best lend themselves to year-round production. A core collection of 20 elite cultivars was next evaluated for nutritional composition, fruit quality, and yields. Thus far, seven varieties are being propagated through in vitro experiments, which includes optimizing conditions to produce more plantlets within a shorter timeframe; acclimatization studies to determine the optimal humidity and temperature regimes to transfer in vitro plantlets to greenhouse or field conditions; salinity studies to determine which varieties are salt-sensitive or salt-tolerant; and tests to determine the optimum method of shipping plantlets to receiving countries.
Pacific Island Ethnobotany
Ethnobotany is the study of how particular cultures use indigenous plants. Many native peoples have extensive and intimate knowledge of the habitats, habits, and properties of the plants where they live. Unfortunately, the traditional knowledge that had once been passed from generation to generation is rapidly disappearing as a result of modernization.
At NTBG, ethnobotanical research in the Pacific Islands is integral to a number of research initiatives, including Restoration Ecology and Breadfruit studies. Traditional knowledge is widely used in the Garden’s educational courses as well.
Data as of May 2006