Long-Term Sustainability of Pacific Island Ecosystems

The Department of Defense (DoD) manages large areas of land in Hawai’i and other Pacific Islands that possess unique biological diversity as a result of their isolated location. The natural biotic communities that DoD manages have become increasingly susceptible to anthropogenic disturbance, be it human development or the introduction of non-native species. In particular, introduced species that have become invasive have altered the composition, structure, and ecological function of Pacific Island ecosystems. Current recovery strategies focused on the eradication of a single species do not recognize that non-native species will likely remain at certain levels and native species extirpations may not be reversed. In addition, future ecological process recovery will need to take climate change and climate variability into account as the resulting impacts may alter remnant ecological processes in these already stressed ecosystems. 

In 2014, SERDP began funding a cohort of projects that are investigating ways to improve the fundamental and applied understanding of ecological processes in the Pacific Islands that have been altered by the introduction of non-native invasive species on lands and near-shore coastal environments managed by the DoD.

Under SERDP project RC-2432, Dr. Christina Liang of the USDA Forest Service Pacific Southwest Research Station and her research team are investigating the impacts of invasive predators' (rodents, ants, and yellow jackets) consumption of animal pollinators on Hawaiian plants. This project combines field observations, experimental manipulations, and laboratory genetic analyses to examine the direct and indirect interactions between native plants, pollinators, and non-native predators. This comprehensive approach will provide a better understanding of current pollinator services and plant reproduction in invaded landscapes.

RC-2433: An example of a fenced enclosure on Pōhakuloa Training Area within which non-native feral goats have been removed. This project will assess the effects of ungulate removal on native ecosystems.

RC-2433: An example of a fenced enclosure on Pōhakuloa Training Area within which non-native feral goats have been removed. This project will assess the effects of ungulate removal on native ecosystems.

Non-native ungulates, such as feral pigs, sheep, and goats, exert a large effect on native biodiversity and the structure and function of native ecosystems on islands throughout the Pacific region; however, non-native ungulate removal is labor and cost intensive. In addition, surprisingly little information is available on the magnitude and time frame of native plant recovery and the response of critical, underlying ecological processes following their removal. Under SERDP project RC-2433, Dr. Creighton M. Litton of the University of Hawai’i at Manoa and his research team are quantifying the recovery of native plant communities and underlying ecological processes following non-native ungulate removal in tropical wet and dry forests on the Island of Hawai’i. By quantifying the mechanisms responsible for patterns following ungulate removal (e.g., changes in ecosystem carbon, nitrogen, and phosphorus cycling, availability, and storage), the project team also will directly test restoration strategies (i.e., soil nutrient manipulation) for increasing native plant species recovery over non-native species.

Under SERDP project RC-2434, Dr. Jeff Foster of the University of New Hampshire and his research team are investigating the effects of non-native invasive birds and rodents on plant communities on the island of Oahu. Specifically, the project team is looking to determine which animals are the major dispersers of seeds from native and non-native plants, what their effects are across the landscape, and how these introduced animals may be shaping the future of plant communities in Hawai’i and throughout the Pacific to enable better natural resource management at Pacific Island military installations. This research will ultimately provide DoD land managers the essential tools for managing and maintaining native plant communities in the Hawaiian Islands and other Pacific Islands and offer meaningful predictive measures of native and non-native plant dispersal and establishment.

RC-2441: Mariana Fruit Dove (Ptilinopus roseicapilla) An example of a native seed dispersing frugivore whose abundance has been reduced on Guam due to invasive species.

RC-2441: Mariana Fruit Dove (Ptilinopus roseicapilla) An example of a native seed dispersing frugivore whose abundance has been reduced on Guam due to invasive species.

Under SERDP project RC-2441, Dr. Haldre Rogers of Rice University and her research team are exploring the impacts of an invasive species on ecosystem function in Guam and developing strategies for restoring function to what is now a novel ecosystem. The invasive brown tree snake (Boiga irregularis) was introduced to the island of Guam in the 1940s. This snake has caused the functional loss of all forest bird species, including all seed dispersers. Island-wide eradication of the snake is unlikely at this time. As a result, this research aims to identify strategies for recovering seed dispersal in the presence of the snake with the ultimate goal of ensuring long-term sustainability of the forests. Results from this project can inform management approaches used for other lands severely impacted by invasive species or extinctions of functionally important species.

RC-2447: ‘O’opu nākea (Awaous guamensis) An example of an at-risk native goby fish in Hawai’i threatened by aquatic invasive species.

RC-2447: ‘O’opu nākea (Awaous guamensis) An example of an at-risk native goby fish in Hawai’i threatened by aquatic invasive species.

Invasive species are primary threats to aquatic biodiversity across the Hawaiian archipelago. In streams on Oahu, where the majority of DoD installations are located, the number of invasive fishes can be an order of magnitude higher than that of native fishes. Although complete eradication of invasive species is often a desired management endpoint, it is rarely feasible because of cost and logistical constraints. With this in mind, under SERDP project RC-2447, Dr. Michael Blum of Tulane University and his research team are examining how a combination of invasive species control and hydrological mitigation can help re-establish ecological functions, boost valued ecosystem services, and enhance native stream fish populations across Oahu. This research will provide defensible and transparent analytical frameworks that can be transferred directly to the DoD as prioritization tools for adaptive watershed management and aquatic species conservation.

For more information on these projects, visit SERDP and ESTCP’s Pacific Island Ecology and Management sub-program area.

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