Developing a Listening Post in the Tropical Pacific: Sensitivity of Hawaiian High-elevation and Aquatic Ecosystems to Global Change

Duration: March 1999 - September 2004

Islands are extremely valuable as living laboratories for understanding species adaptation and evolution. Much as the Galapagos islands provided exceptional insights for Charles Darwin in the 1830s, the more ancient Hawaiian islands have become a world-premier site for modern day studies of evolution in isolated systems.
Organisms of oceanic islands are notoriously susceptible to extinction. Having been isolated for millions of years from some of the selective forces that shape continental organisms, island flora and fauna are uniquely vulnerable to predators, diseases, and competitors introduced by humans. Nevertheless, in spite of extreme human modification of the Hawaiian landscape and biota, large tracts of near-pristine ecosystems remain at high-elevations in protected areas such as Haleakala and Hawaii Volcanoes National Parks. In Hawaii, as well as on other high islands of the Pacific, relatively intact biodiversity is centered in high-elevation cloud forests.
These cloud/rain forests are particularly vulnerable to climate change, since relatively small climate shifts are likely to trigger major local changes in rainfall, cloud cover, and humidity. Such climatic disruptions will undoubtedly favor the penetration of invasive non-native species into previously intact ecosystems.

Mountain cloud/rain forests are critical to the long-term protection of Hawaii’s wealth of locally-evolved biodiversity. They contain thousands of endemic plants and invertebrates, and are probably among most vulnerable of the Earth's ecosystems to global change.

In addition to supporting rich biodiversity and offering unique insights into evolution, mountain cloud forests can serve as potentially valuable "listening posts" in the tropical Pacific Ocean, allowing us to assess climatic stability in the tropics from the present into the near future.In the Hawaiian islands, rainfall, cloud cover, and humidity are largely determined by the position of the North Pacific subtropical anticyclone and the altitude of the trade wind inversion (TWI). The inversion layer represents the level to which clouds normally rise. It roughly corresponds in elevation to the ecotone (transition zone) between the rain forest and the grassland/shrubland that lies upslope.
There are currently two competing models of the potential effects of global climate change on these high-elevation ecosystems. One raises the possibility of increasingly frequent and intense El Niño events (more droughts) combined with a lowering of the TWI. Under this scenario, cloud levels would be lower, there would be less moisture available to plants - particularly at high elevations - and treeline would recede over time. The second model suggests the opposite: A rising TWI, accompanied by an upward migration of vegetation zones, without a marked increase in drought. Evidence for the latter model lies in the fossil pollen record, which suggests that the upper forest limit was higher under warmer climates in the past.We consider the "increasing drought" scenario to be the more likely of the two outcomes. While our research focuses on this scenario, we address the alternative hypothesis in a subcomponent of the project. Our work will be conducted in and around Haleakala and Hawaii Volcanoes National Parks.We will address the possibility of increasingly frequent and intense droughts by: Comparing the microclimatic, hydrological and ecological effects of extreme El Niño conditions with "normal" conditions using a network of microclimate sensing stations we have installed along an elevational gradient on Maui's Haleakala volcano.
Developing and implementing a methodology to detect early changes within the montane rain forest and at its upper limit ("treeline") due to global warming.
Refining and expanding upon previous pollen analyses to determine how the vegetation in high-elevation bogs changed during past warm periods in the earth's history.
We are documenting baseline conditions and responses to El Niño-induced droughts from the heart of the montane forest, up and through treeline, to the mean elevation of the trade wind inversion (TWI). With the microclimatic information and other ecosystem measurements, such as streamflow, we can begin to quantify the sensitivity of Hawaiian montane rain forest and aquatic ecosystems to a regime of increasing drought.We will investigate the alternate possibility of "rising vegetation zones" by: Testing the use of a variety of native and alien aquatic and semi-aquatic species (damselflies and dragonflies) as sensitive and reliable indicators of drought and global climatic change. We will measure biological responses concurrently with microclimate and hydrological measurements
Left: Large tracts of near pristine ecosystems in Haleakala National Park.
Below: Pollen samples from bogs such as this one will provide information on past vegetation.Application of Results:
Information on the relationship between climate and stream flow will be used to estimate the future availability of water for human consumption and agriculture. We will also evaluate, using case studies, a wide range of probable impacts of global change on Hawaiian ecosystems and species that are being managed for protection of biodiversity.

Products:

We will work with the National Park Service at Haleakala National Park to develop interpretive exhibits dealing with weather, climate, streamflow, palynology (pollen analysis of Haleakala’s bogs), and global warming. Exhibits will highlight the expected human dimensions (displacement, migration, increasing urbanization) of global warming for the Pacific region.

We will incorporate our findings into an environmental education program for Maui schools being developed jointly by park (and USGS) personnel and local high school teachers.

Technical publications will analyze responses of high-elevation and aquatic ecosystems to drought and identify likely effects of global warming on selected biota, such as Haleakala silversword, Hawaiian Dark-rumped Petrel, and picture-winged Drosophila.

Collaborators:

Dr. Thomas Giambelluca, University of Hawaii (microclimate and hydrology)
Dr.David Foote, USGS, PIERC (aquatic invertebrates)
Dr. Sarah Hotchkiss (palynology), University of Wisconsin

	Primary Contact: Dr. Lloyd Loope, USGS Pacific Island Ecosystems Research Center More Information: Learn about other projects in the Sensitive Species and Island Ecosystems Research Theme E-mail Dr. Loope