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About the Authors:
Peter H. F. Hobbelen
Current address: Rothamsted Research, Harpenden, Hertfordshire, United Kingdom
Affiliation: Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, Wisconsin, United States of America
Michael D. Samuel
* E-mail: [email protected]
Affiliation: U.S. Geological Survey, Wisconsin Cooperative Wildlife Research Unit, University of Wisconsin, Madison, Wisconsin, United States of America
Dennis A. LaPointe
Affiliation: U.S. Geological Survey, Pacific Island Ecosystems Research Center, Hawaii National Park, Hawaii, United States of America
Carter T. Atkinson
Affiliation: U.S. Geological Survey, Pacific Island Ecosystems Research Center, Hawaii National Park, Hawaii, United States of America
Introduction
More than one-third of all U.S. listed bird species occur in Hawaii, and 71 Hawaiian birds have gone extinct since humans colonized the islands [1]. Introduction of avian malaria (Plasmodium relictum) and its vector, the Southern House Mosquito (Culex quinquefasciatus), are considered primary contributors to population declines of native Hawaiian forest birds [2]. The endemic Hawaiian honeycreepers (Drepanidinae) are particularly susceptible to avian malaria, have one of the highest rates of extinction in the world [3], and many species survive mainly in higher elevation forests that serve as disease refugia [2].
Temporal and spatial dynamics of malaria in Hawaii are driven by seasonal, annual, and elevational weather patterns [4]–[7]. Due to the steep slopes of many Hawaiian Islands, temperature and rainfall changes quickly, creating altitudinal differences in malaria transmission [2], [8], [9] that are characterized by rapid endemic transmission in warm, low-elevation forests to seasonal epidemics in cooler mid-elevations, and little malaria transmission at high-elevations [7]. In Hawaii, both mosquito dynamics and malaria development respond positively to increased temperatures [4], [5], [10]. As a result, global warming is likely to expand the distribution of malaria into high-elevation forests, decreasing the disease-free refuge for Hawaiian honeycreepers [8], [9] and further reducing avian populations.
To reduce future population impacts and potential species extinctions, conservation strategies that reduce the impact of avian malaria on Hawaiian honeycreepers are essential. However, conservation strategies to preserve future populations of Hawaiian birds can be controversial if focused strictly on habitat improvement [11], are likely costly [1], and have considerable uncertainty related to species impacts. Recently, simulation models have been used to evaluate the potential success of different disease mitigation strategies [12], [13], sometimes with differing conclusions...