James D. Jacobi

Modeling Hawaiian Ecosystem Degradation due to Invasive Plants under Current and Future Climates

Occupation of native ecosystems by invasive plant species alters their structure and/or function. In Hawaii, a subset of introduced plants is regarded as extremely harmful due to competitive ability, ecosystem modification, and biogeochemical habitat degradation. By controlling this subset of highly invasive ecosystem modifiers, conservation managers could significantly reduce native ecosystem degradation. To assess the invasibility of vulnerable native ecosystems, we selected a proxy subset of these invasive plants and developed robust ensemble species distribution models to define their respective potential distributions. The combinations of all species models using both binary and continuous habitat suitability projections resulted in estimates of species richness and diversity that were subsequently used to define an invasibility metric. The invasibility metric was defined from species distribution models with <0.7 niche overlap (Warrens I) and relatively discriminative distributions (Area Under the Curve >0.8; True Skill Statistic >0.75) as evaluated per species. Invasibility was further projected onto a 2100 Hawaii regional climate change scenario to assess the change in potential habitat degradation. The distribution defined by the invasibility metric delineates areas of known and potential invasibility under current climate conditions and, when projected into the future, estimates potential reductions in native ecosystem extent due to climate-driven invasive incursion. We have provided the code used to develop these metrics to facilitate their wider use (Code S1). This work will help determine the vulnerability of native-dominated ecosystems to the combined threats of climate change and invasive species, and thus help prioritize ecosystem and species management actions.

Large-Scale Range Collapse of Hawaiian Forest Birds under Climate Change and the Need 21st Century Conservation Options

Hawaiian forest birds serve as an ideal group to explore the extent of climate change impacts on at-risk species. Avian malaria constrains many remaining Hawaiian forest bird species to high elevations where temperatures are too cool for malaria’s life cycle and its principal mosquito vector. The impact of climate change on Hawaiian forest birds has been a recent focus of Hawaiian conservation biology, and has centered on the links between climate and avian malaria. To elucidate the differential impacts of projected climate shifts on species with known varying niches, disease resistance and tolerance, we use a comprehensive database of species sightings, regional climate projections and ensemble distribution models to project distribution shifts for all Hawaiian forest bird species. We illustrate that, under a likely scenario of continued disease-driven distribution limitation, all 10 species with highly reliable models (mostly narrow-ranged, single-island endemics) are expected to lose >50% of their range by 2100. Of those, three are expected to lose all range and three others are expected to lose >90% of their range. Projected range loss was smaller for several of the more widespread species; however improved data and models are necessary to refine future projections. Like other at-risk species, Hawaiian forest birds have specific habitat requirements that limit the possibility of range expansion for most species, as projected expansion is frequently in areas where forest habitat is presently not available (such as recent lava flows). Given the large projected range losses for all species, protecting high elevation forest alone is not an adequate long-term strategy for many species under climate change. We describe the types of additional conservation actions practitioners will likely need to consider, while providing results to help with such considerations.

Population structure and survival of Palila

Annual survival, age, and sex ratios of the endangered Palila (Loxioides bailleui) on Mauna Kea, Hawaii, were determined from multiple captures and resightings of 984 individuals during 1987-1993. The proportion of Second Year (SY) Palila in the population was relatively constant among years, whereas the proportion of Hatching Year (HY) birds ranged from 3.1 to 22.6% over three years. Sex ratios of nestling and SY Palila did not differ from unity, but the sex ratio of HY and ASY Palila was male-biased. Mean proportion of adult males was 63. ± 1.8 SE, and males outnumbered females in all six years of the study. Mean annual survival of HY Palila (0.36 ± 0.08) was lower than that of After Hatching Year (AHY) birds (0.63 ± 0.05), but annual survival of AHY males (0.65 ± 0.07) did not differ from that of AHY females (0.62 ± 0.06). Survival was negatively correlated with annual changes in the availability of green mamane (Sophora chrysophylla) pods, the primary food of Palila. The skewed adult sex ratio may result from greater emigration or mortality of HY females, or from greater mortality of breeding females due to increased exposure to predation

Evaluating the Long-Term Management of Introduced Ungulates to Protect the Palila, an Endangered Bird, and Its Critical Habitat in Subalpine Forest of Mauna Kea, Hawai‘i

Abstract Under the multiple-use paradigm, conflicts may arise when protection of an endangered species must compete with other management objectives. To resolve such a conflict in the Critical Habitat of the endangered Hawaiian honeycreeper, palila (Loxioides bailleui), federal courts ordered the eradication of introduced ungulates responsible for damaging the māmane (Sophora chrysophylla) forest on which palila depend. During 1980–2011, a total of 18,130 sheep (Ovis aries and O. gmelini musimon) and 310 goats (Capra hircus) were removed from Palila Critical Habitat (PCH) primarily by public hunters (54%) and secondarily by aerial shooting. Nevertheless, our analysis indicates that ungulates have increased over time. Palila numbers have declined sharply since 2003 due to long-term habitat degradation by ungulates and drought. Although culling ungulate populations has allowed some habitat improvement, their complete removal is necessary for palila to recover, especially given the potential for continued drought. Introduced predators are being controlled to reduce palila mortality, māmane and other native trees are being planted to restore some areas, and fencing is being constructed to prevent ungulate immigration. Funds are recently available for more effective eradication efforts, which are urgently needed to eliminate browsing damage in PCH and protect the palila from extinction.

The Kahana Valley Ahupua'a, a PABITRA Study Site on O'ahu, Hawaiian Islands

ABSTRACT The acronym PABITRA stands for Pacific-Asia Biodiversity Transect, a network of island sites and conservation professionals collaborating throughout the Pacific-Asia region. An ideal PABITRA site is a broad landscape transect from sea to summit. Such a landscape is Kahana Valley on Windward O‘ahu. Kahana Valley served during prior centuries as an ahupua‘a, a Polynesian unit of land management that integrated the three biological resource zones, the upland forests, the agriculturally used land below, and the coastal zone, into a sustainable human support system. Results of terrestrial biodiversity surveys, as begun with a vegetation/environment study and a paleoecological investigation, are presented in relation to historical land use and sea level changes. In spite of the many former human-induced modifications of the Kahana Valley landscape, the natural structure and function of its ecosystems are well preserved. The distribution patterns of vegetation can be interpreted in terms of Hawaiian ecological zones in combination with the valleys precipitation, topography, stream system, and archaeological features. Currently, efforts are under way to restore the Kahana State Park (recently renamed Ahupua‘a ‘O Kahana State Park) as a functional ahupua‘a. In addition, focused collaborative research can yield helpful information for further restoration and integrated management of the Kahana ahupua‘a as a historic Hawaiian Heritage Site.

Identifying opportunities for long-lasting habitat conservation and restoration in Hawaii’s shifting climate

Conservation efforts in isolated archipelagos such as Hawaii often focus on habitat-based conservation and restoration efforts that benefit multiple species. Unfortunately, identifying locations where such efforts are safer from climatic shifts is still challenging. We aimed to provide a method to approximate these potential habitat shifts for similar data- and research-limited contexts. We modeled the relationship between climate and the potential distribution of native biomes across the Hawaiian archipelago to provide a first approximation of potential native biome shifts under end-of-century projected climate. Our correlative model circumvents the lack of data necessary for the parameterization of mechanistic vegetation models in isolated and data-poor islands. We identified locations consistently expected to remain the same in terms of the native biome compatibility by the end of the century with a robust evaluation of sources of uncertainty in our projections. Our results show that, despite large differences in climate projections considered, 35% of the areas considered are consistently projected to maintain their current compatibility to native biomes. By integrating our native biome compatibility projections with maps of current actual cover, we identified areas ideal for long-term habitat conservation and restoration. Our modeling approach can be used with relatively simple data; offers multiple forms of projection confidence estimates, model calibration, and variable selection routines; and is compatible with ensemble projections. This method is not only applicable to potential native cover, as done in this study, but to any set of vegetation classes that are related to environmental predictors available for modeling.

Dynamics of the Hawaiian Rainforest at Multiple Scales

This paper is a short version of a recently published book ‘Ōhi’a Lehua Rainforest, which resulted from studies of vegetation at multiple scales in space and time. The objective of this short version is not only to demonstrate some of these changes in scale, but also to show that different perspectives through scale changes were needed for synthesizing the subject matter into a coherent story. In other words, any vegetation study that aims at comprehensive explanations needs to view the subject matter from several different perspectives or scales. The five decade-long research on native Hawaiian rainforest is such a study. Following the introduction, this study is summarized under five subheadings: A rainforest born among volcanoes Turnover by auto-succession From rainforest to bog and stream formation Fragmentation into smaller units as islands age Conclusion: the rainforest on Windward O’ahu

High-Resolution Aerial Imagery for Assessing Changes in Canopy Status in Hawai‘i’s ’Ōhi‘a (Metrosideros polymorpha) Rainforest

’Ōhi‘a Lehua (Metrosideros polymorpha) is the most abundant tree species in the native wet and mesic forests throughout the main Hawaiian Islands. In the late 1960s and early 1970s large areas on the wet, eastern side of Hawai‘i island appeared to have extensive defoliation and death of the ’ōhi‘a trees. The dieback on Hawai‘i island extended to approximately 49,000 ha of which 24,000 ha was considered to be in heavy to severe dieback (>50% of the canopy trees dead or defoliated), and 25,000 ha characterized as having slight to moderate dieback (25–50% of the canopy trees dead or defoliated). Research was initiated in 1976 by a team led by Professor Dieter Mueller-Dombois to assess both extent and ecological characteristics of the forest impacted by canopy dieback relative to areas that did not experience dieback in this same forest zone. To assess the spread or recovery of the ’ōhi‘a dieback forest over time, twenty-six permanent plots were established across the study area. The results from the monitoring of the 26 permanent plots indicate that many of the original dieback sites are now showing strong recovery of the ’ōhi‘a tree canopy through recruitment of new seedlings that have now grown into saplings and even taller trees (Boehmer et al. J Veg Sci 24(4):639–650, 2013). However, it was not clear if these results truly represented the conditions across the entire original dieback area. Therefore, we conducted a much larger survey of response of the ’ōhi‘a forest to that dieback event, across the entire wet forest region on the eastern side of the island of Hawai‘i. We did this by analyzing very high-resolution aerial imagery (<10 cm pixels) taken by Pictometry International (POL), to assess both canopy and understory change throughout this region. The POL imagery proved to be an effective and efficient tool to use for assessing the status of ’ōhi‘a forest across the eastern Hawai‘i Island study area. The results of this large area survey, using the POL imagery, agree closely with the conclusions presented by Boehmer et al. (J Veg Sci 24(4):639–650, 2013), that most of the ’ōhi‘a forests on the eastern side of the island of Hawai‘i that were affected by canopy dieback in the 1960s and 1970s have started to recover their tree canopy, as a new cohort of young trees are growing back in these sites.

Hawaiian Islands Coastal Vegetation Survey 2013-2015

This dataset provides information on the current status and various other habitat and descriptive attributes of the native coastal vegetation for seven of the main Hawaiian Islands (i.e., does not include Niihau). This study was focused on identifying sites that still retain relatively intact and highly diverse native coastal plant communities throughout seven of the main Hawaiian Islands (Kaua i, O ahu, Molokai, Lana i, Kaho olawe, Maui, and Hawai i) that may be further impacted by projected sea level rise. The island of Ni ihau was not included in the survey since there is very limited information for this island on its coastal plant community composition and structure, and very-high-resolution imagery is not available to use for assessing the status of its coastal vegetation. Within the identified threatened coastal sites we also attempted to determine if important cultural sites (e.g., Hawaiian house or wall structures, burial sites, etc.) found at there might also be threatened by the projected sea level rise. The results of this study are intended to provide a spatial foundation for identifying priority sites containing native coastal vegetation which can be used for the development of management strategies to help maintain the viability of native coastal plant communities and other important cultural resources found at these sites.

Surveys of forest bird populations found in the vicinity of proposed geothermal project subzones in the district of Puna, Hawaii

This report presents data on the distribution and status of forest bird species found within the vicinity of proposed geothermal resource development on the Island of Hawaii. Potential impacts of the proposed development on the native bird populations found in the project are are addressed.