As the threat to Hawai‘i’s native species and ecosystems grows with each invasive introduction, the Hawai‘i Conservation Alliance’s annual conference has also grown. This year’s conference on restoration had more speakers than ever before.
Highlights of the gathering were the pre sentation of the alliance’s Distinguished Ser vice Award to Hawai‘i Volcanoes National Park resource manager Tim Tunison and the U.S. Fish and Wildlife Service’s David Woodside, and the unveiling of a new series of photographs of the Northwestern Hawaiian Islands by renowned artists Susan Middleton and David Liittschwager.
For most of the several hundred scientists and resource managers in attendance, though, the main attraction of the event was the chance to glean something new or useful from the nearly 100 speakers and 60 posters featured at the conference, and to make new contacts and catch up with old friends. The following is a brief sample of the talks given during the two-day event, held July 28 and 29 at the Hawai‘i Convention Center in Honolulu.
Paleoecology
“What lived in a particular area before European contact? Before Hawaiians arrived? How stable are various major vegeta tion types over time? How do they respond to disturbance? What role did fire play in particu lar Hawaiian ecosystems before European con tact? How has Hawaiian vegetation responded to past climate change? How has vegetation changed with human land use?”
In her abstract for the 2005 conservation conference, University of Wisconsin botanist Sara Hotchkiss argued that paleoecology can help answer all of these questions.
For example, by analyzing soil in Ka‘au crater on O‘ahu, Hotchkiss said, she knows that the uluhe fern (also known as false stag horn fern) is a native species because its pollen is found in samples that are 2,000 years old. She added that the loulu palm (Pritchardia spp.) was once abundant in Ka‘au crater – its pollen makes up 60 to 80 percent of pollen found in soil samples.
Pollen, seeds, snails, charcoal, and trace plant minerals in ancient soils are all keys to the past and can help explain how vegetation composition and structure in a given area changed over time, Hotchkiss said, adding that on Maui, the U.S. Geological Survey is using paleoecology to compare climate change history with vegetation history to see how vegetation may have responded to changes in climate.
“People doing restoration need more than just species lists,” Hotchkiss said. “They need to know how things will respond to climate change or other disturbances. Paleoecological records can give resource managers a dynamic view of an ecosystem over time.”
At Kohala Ranch on the Big Island, for example, where Stanford University researcher Peter Vitousek and others are working, soils and charcoal deposits show that the area vacil lated between grass-dominant periods and ‘ohi‘a-dominant periods over a 20,000-year period. The abundance of charcoal in certain areas can determine how the landscape changed in response to fire, she said – a significant piece of information when plan ning for a stable ecosystem. When restoring an area, one needs to think of “the potential for change – in climates, and various acceler ating changes in land use or ecosystems,” she said
Lost Birds
The remains of the last known po‘ouli were recently returned by the Smithsonian Institute to the Bishop Museum, where it joined the corpses of scores of other extinct Hawaiian birds. Helen James, a bird paleoecologist with the Smithsonian, discussed her work investigating the many bird species Hawai‘i has lost.
Despite development, James said, Hawai‘i has abundant records of ancient birds in dunes, lakes, wetland sediments, and caves. On the older islands, fossils are found mostly in coastal areas. On the younger islands of Maui and Hawai‘i, the records are located inland – especially in lava tubes where flightless birds may have fallen in, where flying birds got lost in the darkness, or where bird bones were washed down with the rain, she said.
By studying the bones and fossils in these areas, one learns “something rather shock ing,” James said: Hawai`i has lost about 90 percent of its native bird species.
In 400 A.D., the islands were home to 107 endemic species. By 1778, when Europeans arrived in the islands, the number of endemic bird species had dropped to 55. As of 2003, only 31 species remained, and of those species, only 11 are not now endangered.
That means that nine in ten birds are “not playing the ecological role they used to play,” James said. This, she continued, raises the question: what was the bird community struc ture originally like? James said Hawai‘i once had abundant predatory birds, terrestrial herbivores, terrestrial omnivores, granivores (finches), arboreal frugivores/omnivores, insectivores, and nectarivores. Judging by the species that are still around today, James said the insectivores are the “winners,” with the losers being the Maui Nui moa-nalo, a duck-like bird whose ancient scat is full of fern spores; a koa finch on Kaua‘i; eagles; hawks; owls; and a crow that used to live on O‘ahu’s ‘Ewa plain. James noted that there used to be three species of crow on Hawai‘i island, two species on O‘ahu, and one on Maui – all of which are extinct.
James said that radio carbon dating indi cates that 20 of the original 107 endemic bird species went extinct after the arrival of the first humans in the islands. She described the swift extinction as a “decapitation,” but said she doesn’t know exactly why human arrival killed so many birds.
Fossil records not only shed light on what’s been lost, they suggest where reintroductions of the few remaining endemic birds could occur. James said fossils of the endangered palila, which is only found on Hawai‘i island, have been found on O‘ahu and Kaua‘i. And fossils of the Laysan duck, which today is known as a coastal bird, have been found in montane sites on Hawai‘i and Maui.
Soil Moisture
A significant percentage of Hawai‘i’s rare and endangered taxa are in dry forests, which cover only ten percent of the area they once did, says Jarrod Thaxton, a researcher with the U.S.Department of Agriculture’s Forest Service. On the Big Island, Thaxton and others are conducting experiments aimed at restoring Hawai‘i’s dry forests.
Among the chief threats to the dry forests are difficult-to-control alien grasses, Thaxton reported. On the Big Island, for example, African fountain grass covers hundreds of thousands of acres and competes with the native plants for light and water. Those com petition effects, however can be mitigated, Thaxton said.
On Kamehameha Schools land in Ka‘upulehu, at the 600-meter elevation, an nual rainfall is about 300 to 500 millimeters (except for 2004, an unusually wet year that brought more than 1000 mm of rain). On this dry landscape, Thaxton, along with the USDA’s Susan Cordell and Colleen Murray, Robert Cabin of the State University of New York at Plattsburgh, and Darren Sandquist of California State University at Fullerton, conducted an experiment where they manipulated light, water, and fountain grass removal through weed-whacking, herbicides, and bull dozing.
The team planted about 1,800 seedlings of ten different species of vines, shrubs and trees in April 2004 and watered them every week for a year. The seedlings were distributed among 36 subplots of 50 each.
In the bulldozed plots, they saw a 50 percent increase in survival over those plots where the fountain grass was left alone. The seedlings in plots that were weed-whacked or treated with herbicide did not grow as well as the bulldozed plot. Plots that had been shaded also saw a 50 percent increase in outplanting survival. Supplemental water had no signifi cant effect on growth.
These results, Thaxton said, suggest that outplanting survival is closely related to soil moisture, noting that in drier times, the grass plots were the driest, while the bulldozed and shaded plots were significantly moister.
Fountain grass limits the natives at least partly though competition for moisture, he said, suggesting that bulldozing might be effective in heavily degraded areas. But bull dozing is not a panacea. He noted that bull dozing may benefit vines and shrubs more than trees, and may produce conditions that favor aliens. Before selecting this technique, he said, you need to define your goals and determine whether you want to increase na tive cover or restore a particular rare plant’s population.
— Teresa Dawson
Volume 16, Number 3 September 2005
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