Photo courtesy of HINHP
Photos: RMyers; HINHP

STRANGERS IN PARADISE:
Alien Plant Species Threaten Hawai`i's Rainforest Birds

Robyn L. Myers, Primary Author; Karen Beardsley, Presenter


Abstract

Hawai`i is unique in many ways, particularly because of the many endemic plant and animal species that have evolved there. It also has the only tropical rainforest in the fifty United States. But in Hawai`i more species also face possible extinction than anywhere else in the US. While the island of Maui has some of the most intact and extensive native rainforests left in Hawai`i today, they are also the most imperiled. A full one-third of Hawai`i's rare, threatened and endangered species occur in Maui's native rainforests, which have the largest concentration of endangered forest birds. Habitat destruction is considered the most important factor in species loss. Research has shown that the spread of alien species currently poses the greatest threat to Hawai`i's rainforest habitats, and the endemic birds and other species that depend on them. This study of the Windward East Maui watershed used a multi-scale approach to identify areas where alien species are posing the most immediate threat of spread into native forest, show how the vegetation canopy has changed over time with the spread of alien species, and identify what different scales of data collection are best for monitoring Hawaiian rainforest bird habitat.


Hawai`i - In the Middle of the Sea

The Hawaiian Islands sit nearly in the center of the Pacific Ocean, and are one of the most isolated island groups in the world. In Hawai`i, more species face possible extinction than anywhere else in the United States. Of Hawai`i's rare, threatened and endangered species, one third are found only on the island of Maui. Maui's native rainforests are among the most imperiled in the world, with the largest concentration of endangered forest birds in Hawai`i. Hawai`i's endangered forest birds evolved in isolation. From a few colonizing individuals over 140 species evolved, providing one of the best examples of adaptive radiation in the world

The first formal surveys of Hawai`i's forest birds were taken in the mid 1970's to early 1980's during the Hawai`i Forest Bird Survey. Coordinated by Dr. Mike Scott and others, the Hawaiian Forest Bird Surveys were conducted on the islands of Hawai`i, Lana`i, Moloka`i and Maui. A multi-disciplinary team approach was used to simultaneously map the distribution of birds, selected food items, and major vegetation types in Native Hawaiian rainforest. The work is often considered the first "gap analysis." The primary objectives were to determine:

A series of parallel transects were laid out perpendicular to the elevational contours. The first transect was randomly located, with the remainder systematically placed. Sampling was then conducted at stations established at regular intervals along the transects. There are thirteen transects in the East Maui watershed that are considered permenant, and are still being used for bird, threat and ecosystem monitoring. This research was based on HFBS recommendation for further study and monitoring of established bird transects and the rainforest habitat, at finer detail.

Research in Hawai`i has shown that habitat destruction is the most important factor in species loss. Native plants and animals are vulnerable to habitat destruction and displacement by the invasion of alien species. Many alien plant and animal species were purposely introduced. For example, the Polynesians brought taro and banana, the Europeans brought African tulip trees for gardens, and more recently, eucalyptus were planted as wind breaks and for timber. But some of these aliens have grown to be a major problem in Hawai`i. European boar mixed with the smaller Polynesian pigs to create an alien that destroys native forest. Alien plants often invade areas disturbed by pigs. One species, Miconia calvescens has prompted a coordinated state wide effort to eradicate it. This species took over the island of Tahiti in the last 40 years, and is invading Hawai`i, threatening Hawaiian forest bird habitat and other native species.

In 1991, seven concerned landowners formed the East Maui Watershed Partnership (EMWP) to coordinate the resource management of 4,047 hectares (100,000 acres) of watershed ecosystem. They were concerned with coordinating efforts to manage and monitor the watershed. Two of the EMWP goals were: To develop and implement a long term inventory and management plan for the greater watershed; and To provide a strategy to target known alien species, and prevent new alien species from entering the watershed. The research reported here was designed to help meet those priorities by: (1) building on the Hawaiian Forest Bird Survey, going to the next level of detail; (2) coordinate with local agencies and researchers; (3) Use a landscape ecology approach to analyze spatial and temporal change; (4) use GIS and remote sensing as the primary analysis tools.

The research area is the Windward East Maui Watershed, a 100,000 acre (40,470 hectare) area extending from the Northern coast to the summit of Haleakala volcano, and from sea level to 10,000 feet. The Ke'anae Valley-Ko'olau Gap Focus Area is a 12 mile long by 2 mile wide valley from sea level to about 8000' elevation, where more detailed study and ground observations were made.

The over all research objectives were to:

There were three research questions:

Why use a Multi-Scale approach? Conservation generally takes place at a landscape level with parks and preserves protecting large areas. Traditional ecology research takes place at the species or community level, studying individuals or populations. The challenge is to integrate the two while focusing on an area that can be both studied and managed.

The Tri-Scale Convergent Hierarchy Approach considers three scales for both research and conservation:

A complete diagram of TriSCHA applied to East Maui, and further details on the approach of this research can be found at http://ice.ucdavis.edu/~robyn/introppt/index.htm

Watershed and Gap Analysis

Q 1: Is the presence and extent of alien species associated with certain land use types and landscape variables?

The Watershed and Gap Analysis was primarily a GIS overlay analysis conducted in PC ARCView. Most of the base data layers were provided for this project from the Hawai`i Office of State Planning The Nature Conservancy of Hawai`i, Hawai`i Natural Heritage Program. Data were generally received in ARC/INFO export format. The data were imported initially into UNIX ARC/INFO then to PC ARCView for development and analysis. Some data were brought in directly as shape files in ASCII format. Ground survey data were linked by GPS coordinates, or by location of individual plants in digital orthophotos, to the GIS.

Data layers included vegetation cover, management type and observations of rare, threatened and endangered species, and other data layers such as elevation and rainfall. In cases where new overlay data were needed for analysis, shape file data were exported into UNIX ARC/INFO, converted to coverages, and traditional "union" overlays were created. These coverages were then immediately exported back into ARCView for analysis. In most cases, cross-tabulations conducted in Microsoft Access, directly from the shape file database (dbf) files, provided summary statistics. SPSS for Windows provided more detailed statistical of these tables when desired.

The results of the watershed and gap analysis showed that most of the native and alien species occur in the multiple use management areas, and therefore more study and coordinated management is needed. Inventory and monitoring efforts should continue, with GPS ground surveys and air photos every 8-10 years, and hot spots monitored by aircraft based remote sensing.

A complete web version of the Powerpoint presentation on the Watershed and Gap Analysis portion of this research can be found at http://ice.ucdavis.edu/~robyn/gapppt/index.htm

Vegetation Change Over Time

Q 2: Can canopy species change be interpreted from historic aerial photos?

Using historical literature as a background of vegetation and land use change for the years prior to aerial photography.

The historic land-use and vegetation literature review began with records describing the land and vegetation prior to the arrival Polynesians, and continued to present time. Lava upwelling from a hot spot in the Pacific built the Hawaiian islands over 70 million years. Archeological and paleontological literature described the arrival and evolution of native species by wind, sea and storm. Species arrived primarily from the Americas and Asia. Once every 100,000 years a new species survived and established itself. These species evolved into over 12,000 new endemic species. Research has shown that species differ from island to island, and in some cases, even from valley to valley.

The arrival of Polynesians led to the introduction Polynesian species, and agriculture, and the co-evolution of the Hawaiians with the landscape. Extinctions accelerated with the Europeans after the arrival of Captain Cook in 1778. Europeans introduced cattle, goats and boars. By the mid 1800's "Sugar cane was King" in the fertile lowlands, thriving on water diverted from the forests. More recent historical records and reports documented influence of the Europeans on the landscape, with continued land development, as well as the introduction and spread of alien species. Current reports on Maui describe modern research to document native, Polynesian and alien species, and the coordinated conservation efforts to protect them.

After all this time, what is gone? Nearly 75% of the nation's documented extinctions are from Hawai`i. Of at least 140 species of native birds, 70 species are extinct. Of the 70 surviving, 30 are endangered. The list of endangered plants is approaching 100 species. 60 species have only 100 individuals left, 31 have less than 10, and 6 have only 1 individual left.

And alien species continue to spread. Local land managers observed species spreading up the Ke'anae Valley over the last 40 years. This spread may have been exacerbated by areas of previous Hawaiian cultivation, long left fallow, that now have a thick growth of alien species. Land managers had observed these changes on various sets of aerial photos over the years. But with each set of photos at different scales, it was difficult to follow and measure these change through time.

Photography for East Maui begins in the early 1950's. A chronosequence of historic aerial photos was created for the Ke`anae Valley focus area of East Maui, including photos from 1951, 1965, 1978, 1991, 1995 were analyzed to detect and measure these changes in vegetation.

The historic aerial photos were digitized at 250 dpi (dots per inch), the photos provide approximately 1 meter pixel resolution. The images were then orthocorrected using softcopy mapping techniques, and then brought into ARCView as TIFF images. This allows the various photo years to be viewed at the same scale, and with other data layers overlaid. Current vegetation classes were interpreted from the paper stereo pairs of the 1995 color infrared photos, and these vegetation boundaries digitized on screen using the orthorectified image as backdrop. The 1995 vegetation boundary polygons were overlaid on the other historic aerial photo images, and the polygons edited to the vegetation of that year. Both areas of individual polygons, and the vegetation they contained could be tracked through time.

The results of the landuse history and vegetation change over time show ly carried out a ground pilot monitoring project to develop and refine the ground transect monitoring methods. GPS points were collected along transects, and these data were included in the GIS.

The Landsat Thematic Mapper proved to be too cloud covered and the resolution to coarse to map more than the most general vegetation types. This was also true of the SPOT Multi-Spectral 20 meter images. The SPOT Panchromatic 10 meter may prove useful as an aide to orthocorrection of smaller scale data, and for middle detail level mapping. The aircraft based remote sensing, (in this case provided by NASA's C-130 NS001 Thematic Mapper Simulator at 7 meter resolution) provided good vegetation canopy detail, and multiple spectral bands for more detailed analysis. It was, however, very difficult to orthocorrect due to the "roll, pitch and yaw" of the aircraft, the uneven terrain, and a lack of ground control points for most the Ke`anae Valley. However, with image processing software and a digital ortho photo or quadrangle, it is not impossible to do. The digital orthophoto mosaic had to be contracted out to softcopy photogrammetric specialists. Diapositives of the air photos had to scanned, and then orthocorrected using specialized software and techniques. In the last few years both the availability and cost for this sort photo orthocorrection has improved substantially. And, again, ground monitoring, whether in formal transects or ground checks of aerial photo mapping is essential. These data can be integrated into the GIS with the collection of GPS points.

This work resulted in three reports published by The Nature Conservancy of Hawai`i, in addition to my dissertation research:

I recommended that current satellite remote sensing (TM and SPOT) is best used for more general land cover mapping. Aircraft based remote sensing, coupled with digital aerial photography can provide good vegetation detail, and that these should be coupled with ground transects the monitoring the native Hawaiian rainforests of the East Maui watershed.

A complete web version of the Powerpoint presentation on the Multi-Scale Analysis portion of this research can be found in a at http://ice.ucdavis.edu/~robyn/multisclppt/index.htm


Acknowledgements

I would like to wish mahalo nui loa to The Nature Conservancy of Hawai`i, the Hawai`i Natural Heritage Program, the Hawai`i Office of State Planning, Advanced Mapping Technologies, the NASA Ames Research Center, the USDA Natural Resources Conservation Service, the Charles Lindbergh Foundation, and the University of California Davis Information Center for the Envrionment.


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Author Information

Robyn L. Myers
Ph.D. Candidate, Graduate Group in Ecology, University of California, Davis
Affiliate Scientist, NRCS Watershed Science Institute
Landscape Ecologist, Water Resources Planning
USDA Natural Resources Conservation Service
2121-C 2nd Street, Davis, CA 95616
email: rmyers@ca.nrcs.usda.gov
http://ice.ucdavis.edu/~robyn

Karen Beardsley
GIS Coordinator, Information Center for the Environment
Division of Environmental Studies
University of California, Davis
Davis, California 95616
Telephone: (916) 752-4389
Fax: (916) 752-3350
E-mail: kbeardsley@ucdavis.edu