The impacts of albatross (Phoebastria immutabilis), Black-footed albatross (Phoebastria nigripes), and Bonin petrel (Pterodroma hypoleuca) on coastal native outplantings at Midway Atoll National Wildlife Refuge

Jacqueline C. Smith Spring 2020

Committee Members: Dr. Travis Idol, Ph.D Dr. Catherine Chan, Ph.D Dr. Mehana Vaughan, Ph.D

Natural Resources and Environmental Management in the College of Tropical Agriculture and Human Resources University of Hawai’i at Mānoa

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TABLE AND FIGURE LIST PAGE

Figure 1: Seabird Entrapment ...... 21

Figure 2: Native Evaluated ...... 21

Figure 3: Restoration Sites ...... 22

Figure 4: Survivorship of E. variabilis, C. oahuense, ...... 22

and S. taccada by site and size class

Figure 5: Species Survivorship by Site ...... 23

Figure 6: Seabird Damage ...... 23

Table 1: Inventory ...... 24

Table 2: Statistical Outputs ...... 25

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I) EXECUTIVE SUMMARY Midway Atoll National Wildlife Refuge (MANWR) is the largest colony of nesting albatrosses in the world. Seabirds are key environmental drivers for island health but are negatively affected by erosion from sea level rise. Planting native species is a cost-effective method to combat erosion and to optimize seabird habitat. However, seabirds defoliate plants for nesting material resulting in reduced plant survivorship. Historically, MANWR staff used plastic fencing to protect new outplantings but this method is costly in terms of time, cost, and labor with risk of seabird entrapment and mortality. This project investigated the efficacy of fencing at four existing restoration sites on Sand island. I hypothesized that fencing would increase survivorship in all species and size classes across the island. In Fall 2017, four restoration sites were outplanted by MANWR staff with six native plant species (Eragrostis variabilis, Scaevola taccada, oahuense, Fimbristylis cymosa, Sesuvium portulacastrum, and Lepidium bidentatum) in three size classes with and without fencing. Biweekly from November 2017 to March 2018 plants were measured for height, circumference, total number of woody stems, length of longest stem, and the total number of stems. In June 2018 plants were screened for survivorship. Small (p = 0.0001727) and Medium (p = 0.02918) fenced S. taccada plants were statistically significant (p < 0.05) for height using Welch’s two sample t-test. Based on these findings, fencing can be avoided if larger plant sizes are deployed in the field and plant species are chosen to match site characteristics. Recommendations for plant species, nursery practices, and in-field practices are provided along with suggested future research opportunities.

II) MOTIVATION Midway Atoll is home to more than 20 species of seabirds and is the largest colony of nesting albatrosses in the world. Approximately 2 million albatross nest or rest at Midway yearly (Midway Atoll Conceptual Site Plan, 2008). However seabirds are losing nesting habitat due to beach erosion from sea level rise. The U.S. Fish and Wildlife Service (USFWS) developed the Papahānaumokuākea Monument Management Plan (PMMP) to address multiple overarching issues. Native plants are cost effective alternatives to maintain coastal sand dunes since they are adapted to the local environment. Through the use of native plants the PMNM is mitigating these global issues on a local level. Completed in December 2008, it was the result of an extensive public review process and identified six priority management needs with supporting action plans and corresponding desired outcomes, for the Papahānaumokuākea Marine National Monument (PMNM). The 6 priorities are: (1) Understanding and Interpreting the Northwestern Hawaiian Islands; (2) Conserving Wildlife and Habitats; (3) Reducing Threats to Monument Resources; 4

(4) Managing Human Uses; (5) Coordinating Conservation and Management Activities; and (6) Achieving Effective Monument Operations (National Oceanic and Atmospheric Administration, 2008)

As evidenced by these priorities, protecting the land and waters of the Northwest Hawaiian islands (NWHI) from the impacts of alien species like Verbesina encelioides (golden crownbeard) is critical to achieving the Monument’s priorities of resource protection. A specific component of Priority 3 was the development of an Alien Species Action Plan (ASAP). The ASAP advanced a series of strategies to address and mitigate the ongoing effects of invasive plant and animal species on the PMNM (National Oceanic and Atmospheric Administration, 2008). Specifically, the ASAP identified the eradication of V. encelioides and replacing with native plants best for nesting seabirds across the entire atoll. MANWR managers have found that native plants provide optimal habitat, use less water and nutrients, and require less labor to maintain long term compared to introduced plant species (Wilkinson et al., 2014). With these goals in place, site managers of MANWR were willing to collaborate with me in the selection, design, and collection of data for this research project. This research specifically addresses priorities (1), (2), (5), and (6) of PMMP’s goals. Infrastructure and outplanting protocol were already established on Midway along with a volunteer crew for fencing and data collection. These are the major factors that made this research opportunity possible.

III) BACKGROUND The risks of accelerated sea-level rise associated with climate change are exacerbated by increases in the frequency of extreme tides changes, waves and the strength of storm surges (Menéndez & Woodworth, 2010), resulting in a higher intensity and frequency of flooding and erosion of vulnerable coastal areas. Observations and numerical analysis have shown that significant wave-height variations are clearly linked to climate modes (Menéndez et al., 2008; Duarte, 2013) and that wave heights have increased in the North Pacific, North Atlantic, and Southern Ocean during the past century (Hemer et al., 2010; Izaguirre et al., 2011; Young et al., 2011). Sea level has been rising globally at an average rate of 1.6±0.2 mm yr–1 since 1901 (Church & White, 2011), and moderate emission scenarios project a future global mean sea-level rise of 0.21–0.48 m by 2100 (Stocker et al., 2007; Soloman et al., 2007). The Intergovernmental Panel on Climate Change (IPCC) 2019 special report confirms that global mean sea level is rising (virtually certain) and accelerating (high confidence). Coastal ecosystems are already impacted by the combination of sea level rise (SLR), other climate-related ocean changes, and adverse 5 effects from human activities on ocean and land (high confidence) (Oppenheimer et al., 2019). Even if wave projections carry substantial uncertainty, the direct connection between wind and storminess indicates that climate change is likely to have a significant impact on wave heights and other wave parameters (Kundzewicz et al., 2014). As a result, coastal flooding and erosion will be, and are already becoming, a major threat to coastal areas, demanding the introduction of sustainable measures to cope with this problem. Coastal flooding and erosion are being addressed on Midway through native outplantings. Native plants recover natural vegetative composition, structure and successional patterns, protect biodiversity and plant genetic resources, provide habitat connectivity, maintain plant and pollinator interactions, support wildlife populations, increase system resilience to disturbances and stressors, provide desired goods, services, and benefits, and provide economic benefit to rural communities (Wilkinson et al., 2014). Coastal sand beaches and dunes are important but understudied arbiters of coastal ecosystem services. They form at low-lying coastal margins where sand transported by oceanic waves and wind combine with vegetation to produce dynamic geomorphic structures. Thus, sandy-shore ecosystems include both marine and terrestrial components and vary, depending on sand supply, in the extent to which the beach versus the dune dominates (Short and Hesp, 1982; Barbier et al., 2011). Coastal beaches and dunes have provided humans with important services such as raw materials, coastal protection, erosion control, water catchment and purification, maintenance of wildlife, carbon sequestration, tourism, recreation, education, and research (Carter, 2013; Pye and Tsoar, 2008; Barbier et al., 2011). Dune formation in coastal areas implies both sand accumulation and erosion, depending on the existing micro-topography (Moreno-Casasola, 1986). Plant colonization accelerates the growth of dunes because surface roughness in the form of vegetation decreases wind flow and increases sand deposition (Chapman, 2016; Olson, 1958; Ranwell, 1972). Dune erosion usually takes place in the areas where the vegetation cover has become damaged. The dune system is very dynamic in time and space (Moreno- Casasola, 1986). Midway managers currently use native plants to repair damaged coastal dune systems. A native plant is a species that occurs naturally in a particular region, ecosystem and/or habitat and was present prior to human settlement. Native plants have evolved to thrive in natural conditions and, after the first season or two of establishment, typically require less maintenance than non-native species. Natives are adapted to the geography, hydrology, and climate of that region (Wilkinson et al., 2014). As a result, a community of native plants provides optimal habitat for a variety of native wildlife species such as seabirds, sea turtles, and monk seals (NOAA 2007). Located on the far northern end of the Hawaiian archipelago, Midway Atoll National Wildlife Refuge (MANWR) is within the Papahānaumokuākea Marine National Monument (PMNM). It is one the oldest atoll formations in the world providing nesting habitat for millions of seabirds (Midway Atoll NWR). The monument is the largest contiguous fully 6 protected conservation area under the U.S. flag, and one of the largest marine conservation areas in the world. It encompasses 1,508,870 square kilometers of the Pacific Ocean. The monument was established in 2006 and later expanded in 2016 by President Barack Obama, nearly the size of the Gulf of Mexico, making it the biggest protected area, terrestrial or marine, on the planet (Papahānaumokuākea Marine National Monument, 2017). Major milestones that influenced ecology of Midway include the importation of approximately 9,000 tons of soil with vertebrate, invertebrate, and arthropod introductions in 1903, to The Battle of Midway on June 3rd 1942 and being an active naval base, to becoming a national wildlife refuge in 1988. Human influence is prevalent throughout the landscape and conservation and/or restoration efforts to improve the nesting habitat for native birds, mammals, reptiles, fish, invertebrates, and plants is on- going (Preserving the Past, 2015). The high density of large-bodied birds nesting in close proximity is potentially responsible for the partial instability of the plant communities in which they live (Gillham, 1961) along with historical direct and indirect human impacts (guano extraction, albatross egg harvesting, and active military base) (Brief History of Midway Atoll, 2019). Midway Atoll is a highly disturbed system that hosts invasive plant species, toxic materials, and human development remnants that, taken together, have created significant adverse impact on indigenous species and their habitat. Efforts focus on restoring atoll habitat and enhancing species populations (Shluker, 1999). Currently, the habitat restoration scheme includes the propagation and reintroduction of native Hawaiian plant species back into their environments along with the systematic removal of invasive mammalian and plant species including mice and top-priority weeds such as V. encelioides (golden crownbeard) from within the landscape. Verbesina presents a significant problem of habitat degradation for seabirds and native plants including the decrease of potential nesting habitat, inhibition of native plant growth, allelopathic effects inhibiting native plant growth, and wildlife entanglement (Shluker, 1999). Common native plant species utilized in outplantings include juvenile Eragrostis variabilis, Scaevola taccada, and Chenopodium oahuense. However, small size class are prone to damage or mortality by defoliation from nesting seabirds and abiotic factors such as drought, saltspray, and wind damage (Holthuijzen, 2017). Fencing has historically been used to reduce damage from seabirds; however, it is both time- and labor-intensive with the risk of animal entrapment (Pterodroma hypoleuca) within or under the fence (Starr, 2008). Seabird Breeding Behavior and Habitat Management Implications Ocean bird species nest on offshore islands where there is a combination of suitable habitat (Ricklefs, 1990) and an absence of predators and human disturbance (Burger and Gochfeld, 1993). These animals provide environmental services such as nutrient deposition, providing uncolonized habitat through burrowing, seed dispersal, and 7 maintaining open areas within the landscape (Ellis, 2005). Seabirds are chemical and physical engineers that are capable of transforming terrestrial vegetation by altering edaphic conditions, generating physical disturbance, and affecting seed dispersal. Seabirds also have the capacity to introduce large amounts of marine-derived nutrients to land, thereby altering resource availability to terrestrial species (Anderson and Polis, 1999; Mulder and Keall, 2001; Vidal et al,. 2003). The activities of nesting seabirds impact important factors to plants including resource availability, disturbance, and seed dispersal. Through foraging in marine habitats and breeding on land, seabirds deposit prey remains, carcasses, feathers, eggshells, and guano in terrestrial systems (Ellis, 2005). Seabirds also generate a considerable amount of physical disturbance through their nesting activities (Ellis, 2005). Burrowing as well as activities that directly damage plant tissues (trampling, uprooting, and pulling leaves off plants) may play a large role in plant community dynamics in and around seabird colonies. Several studies have shown that seabirds can be important agents of seed dispersal (Ellis 2005), thereby influencing plant recruitment. Therefore, a reduction in seabird populations is likely to have negative consequences for native plant species that rely on seabird disturbance for their persistence (Ellis, 2005). Natal philopatry, the tendency for animals to return to breed near their birthplace, is well developed in colonial nesting seabirds (Warham, 1990). In recent years, concern has grown about the increasing vulnerability of the NWHI and their wildlife populations to changing climatic patterns, particularly the uncertainty associated with potential impacts from global SLR and storms (Reynolds et al., 2012). If current climate change trends continue, rising sea levels will inundate low-lying islands across the globe, placing all island biodiversity at risk. The NWHI supports the largest tropical seabird rookery in the world, providing breeding habitat for 20 species of seabirds, 4 endemic land bird species, and essential foraging, breeding, or haul-out habitat for other resident and migratory wildlife. Reductions in limited habitat types due to rising sea levels disproportionally impact philopatric seabirds that may have limited adaptation potential to respond to habitat changes (Laidre et al., 2008). The loss of nesting grounds on islands due to inundation and coastal erosion will directly reduce the survival and reproduction of globally important avian populations (Reynolds et al., 2012). At Midway Atoll, substantial habitat loss is predicted for several globally important populations: one of the largest colonies of Bonin Petrel (Moore, 2009) and the world’s largest colonies of Black-footed and Laysan albatross that represent one-third and three- quarters of the world’s breeding populations, respectively (Flint, 2011).

Bonin Petrels (Pterodroma hypoleuca) The Bonin petrel is a small, burrow-nesting seabird that breeds colonially throughout northern winters. It breeds farther north than any other Pterodroma, or gadfly petrel, in the Pacific Ocean. The Hawaiian population breeds on sandy, grassy areas on 8 small, low coral atolls at sea level. Breeding is confined to these small islands because of predation elsewhere at otherwise appropriate sites (Reynolds et al., 2012). Birds burrow into soil, generally under vegetation such as native bunchgrass (E. variabilis). They prefer soft sandy soil but are known to nest in low densities on maintained lawns and under stands of ironwood (Casuarina equisetifolia) trees on Midway Atoll and under dense native naupaka (Scaevola sericea) shrubs on (Reynolds et al., 2012; Clapp, 1975; Seto, 1999). The roots of native plant species typically provide better substrate stability than non-natives. As a result, petrels typically induce damage to the root system while burrowing beneath outplantings. If the plant is fenced there is also high risk hazard for death from bird entrapment (Figure 1).

North Pacific Albatrosses (Phoebastria) Both Laysan (Phoebastria immutabilis) and Black-footed albatross (P. nigripes) are ground-nesting seabirds. They nest for the most part on remote beaches in the Hawaiian archipelago during the northern winter and spring, and then wander widely across North Pacific waters but usually nest in grass or sand, often close to vegetation, although thick grass can inhibit nesting (Awkerman et al., 2009).

Native Plant Physical Descriptions Bunchgrass (E. variabilis) [Kāwelu] is a perennial grass which is variable in appearance. The smooth, erect stems grow up to 0.914 meters tall or more, with leaves and that are variable in length (Figure 2-A). The panicles are open and spreading or dense and spike-shaped. This plant grows in several types of island habitat from dunes at sea level to ridges and cliffs at up to 1127 meters in elevation. It grows in areas that receive 1016 to 2540 milimeters of precipitation per year. On Midway Atoll this plant provides nesting habitat for seabirds in this study. It is used by other bird species, such as the brown noddy (Anous stolidus), wedge-tailed shearwater (Puffinus pacificus), and red- tailed tropicbird (Phaethon rubricauda). The displacement of this species by invasive weeds reduces the amount of available nesting habitat for birds (Flint and Rehkemper, 2002). This plant was used as thatching by Native Hawaiians. It is also used as an ornamental grass (Joy, 2009). Beach naupaka (S. taccada) [Naupaka] is a large bush reaching about 4 m in height typically in littoral zones where it grows very close to the sea exposed to the salt spray, usually on sandy or pebbly soils (Scaevola taccada, 2009). Leaves are slightly succulent, about 20 cm long, closely alternate and crowded at the stem tips. They are glabrous with a fleshy-looking yellowish green color. The fruits and flowers are white (Figure 2-B). Naupaka blooms the whole year round and the flowers have a fan-like shape which gives them the name fanflower or half flower. The fruits float in seawater and are propagated by ocean currents, this bush being one of the pioneer plants in new sandbanks in tropical areas (Hyland et al., 2010). Naupaka is used to prevent coastal erosion as well as for 9 landscaping. It is also planted on the beach crests to protect other cultivated plants from the salt spray. Parts of the plant are also used in Polynesian and Asian traditional medicine (Global Invasive Species Database, 2018). Hawaiian goosefoot (C. oahuense) [ʻĀweoweo] is a shrub that can reach 5 to 20 meters in height. The fleshy, slightly hairy leaf blades have three lobes and the is a panicle of small flowers (Figure 2-C) (Duvauchelle, 2009). This plant can be used for Hawaiian ecosystem restoration and erosion control. Sooty terns and red- footed boobies use this plant as nesting material. The Hawaiian people used the wood of this plant to make shark hooks, and the cooked leaves were eaten like . It is salt-, wind-, drought-, and heat-tolerant (Chenopodium oahuense, 2009).

Sea purslane (Sesuvium portulacastrum) [Akulikuli] is a sprawling perennial herb up to 30 centimetres high, with thick, smooth stems up to 1 metre long. It has smooth, fleshy, glossy green leaves that are linear or lanceolate, from 10–70 millimetres long and 2–15 millimetres wide (Figure 2-D). Flowers are pink or purple (Prescott, 1984). Akulikuli grows in sandy clay, coastal limestone and sandstone, tidal flats and salt marshes (Western Australian Herbarium, 1998). It is tolerant of waterlogged soil, drought, brackish water, wind, salt spray, foot traffic, and heat (Sesuvium portulacastrum, 2009).

Button sedge (Fimbristylis cymosa) [Mauʻu ʻakiʻaki] is a non-woody, clumping, sedge. It grows 0.3 to 0.75 meters in height and is common on sandy beaches and in shallow sand or silt on and among rocks and cracks in lava. Button sedge does not have the characteristic sharp-edged leaves that many other sedges are known for. Instead the leaves are short, stiff and pointed and thus well suited for its harsh coastal environment (Figure 2-E). The plant has clustered flower and seed spikelets that range from rusty brown to grayish brown (Fimbristylis cymosa, 2009).

Peppergrass (Lepidium bidentatum) [Kūnānā] forms loose, small, herbaceous shrubs to dense covering as a groundcover (Figure 2-F). The edible leaves have a peppery smell and flavor to them and can be added to spice up green salads. The plant root was also used in early Hawaiian medicine (Lepidium bidentatum, 2009).

IV) OBJECTIVES The overarching objective is to enhance optimal habitat for endangered seabirds threatened by sea level rise. This will be accomplished through the support of the Papahānaumokuākea Monument Management Plan’s priorities: (1) Conserve Wildlife and Habitats; (2) Reduce Threats to Monument Resources; (5) Coordinate Conservation and Management Activities; and (6) Achieve Effective Monument Operations (National Oceanic and Atmospheric Administration, 2008). These were executed through the following activities: 10

• Evaluate the survivorship of six native plant species already planted by MANWR staff at four established restoration sites. • Preliminary investigation of the relationship between plant size and fencing measured through survivorship. • Assessment of survivorship of those species with or without fencing. • Descriptive analysis of plant survival by site, species, and size.

V) APPROACH Site Selection There are four major restoration sites across Sand Island: ’Iwa, Bulky Dump, Cable House, and Demo 16 (Figure 3). They were selected based on available size classes of already planted natives. Experimental plots included a minimum of ten individuals or clusters of individuals fifteen centimeters or closer to each other with similar mass within a size class. Of the ten individuals or clusters of each species, five had fencing and five remained unfenced. Monitored plants included the following: E. variabilis, S. taccada, S. portulacastrum, F. cymosa, C. oahuense, and L. bidentatum and had different size values within each size class based off morphology. Plant and Plot Identification All plants included in this study had an adjacent circus stake tied with survey tape for easy detection. Individuals were labeled with the site initial followed by the plant initial and the size class followed by the assigned plant number within the group series (1 through 10). Plant Size Classes at Sites Bulky Dump (Figure 3-A) consisted of outplantings of E. variabilis Unknown (35- 110 cm) and Small (25-100 cm) size classes, S. portulacastrum (5-42 cm) Small size class, F. cymosa (15-40 cm) Small size class, and C. oahuense (2-38 cm) Small class comparing fenced versus non-fenced. Note: At the Bulky Dump site, the only available plants varied in size and were placed in the Unknown size category. Sizes ranged from 35-110 cm. Cable House (Figure 3-B) contained outplantings of E. variabilis (43-100 cm), F. cymosa (30-45 cm), L. bidentatum (24-38 cm), and C. oahuense (32-43 cm), in the Small size class. Data collection at this site focused primarily on assessing differences in fenced and non-fenced plants rather than changes between size classes. Demo 16 (Figure 3-C) included outplantings of E. variabilis and C. oahuense. Size ranges included Small E. variabilis (60-160 cm), Small C. oahuense (15-68 cm) and one Large C. oahuense (68 cm) as a reference. When categorizing plant size at the sites, recorders will assumed a positive correlation between plant age and plant size. 11

‘Iwa (Figure 3-D) site consisted of Large, Medium, and Small plants and the species E. variabilis and S. taccada. Plants from the Large age class were outplanted on 18 March 2017. E. variabilis large class ranged from 73-100 cm in height and corresponding S. taccada size class ranged from 7-30 cm in height. The Medium age class was outplanted on two separate dates: 14 June 2017 and 27 June 2017. E. variabilis (98-144 cm) was planted on both occasions while S. taccada (55-79 cm) was planted only on 27 June 2017. E. variabilis (73-108 cm) and S. taccada (14-30 cm) in the Small age class were planted on 9 August 2017. Plant Measuring Methodology Because of the wide range of plant types and morphology among species, species- appropriate measurements were used to track temporal plant growth and damage. Measurements for E. variabilis included the height of longest stem and the circumference at the base of the plant (cm). If more than one plant occured within a fence and the space between the plants was not large enough for an adult albatross to walk between plants, the diameters of individual plants were summed and the height of the longest stem from the ground of all plants (cm) was recorded. S. taccada measurements included measuring the height of the plant from the highest point (cm) and the number of major stems emerging from the ground. S. portulacastrum measurements were the length of longest stem (cm) and the total number of stems (cm). Measurements of F. cymosa included the base stem diameter and recording the total height of plant (cm). Data recorded for L. bidentatum included the total number of stems and the total height of each plant. Finally, C. oahuense measurements included the total number of woody stems and the height of tallest plant. Measurements began on 18 November 2017 and continued for the first six months biweekly afterwhich all fences were removed with measurements recorded monthly for four months and a final plant evaluation was conducted on 26 June 2018. Statistical Data Analysis The quantitative data were analyzed using R version 3.6.2 and Microsoft Excel version 14.5.2 statistical software programs. A Welch’s two-sample t-test (p < 0.05) was applied to compare the statistical significance of fenced versus non-fenced plant populations.

H0: There is no difference between fenced and unfenced plant populations (species specific measurements: height, circumference, total number of woody stems). H1: There is a difference between fenced and unfenced plant populations (species specific measurements: height, circumference, total number of woody stems).

Welch’s two-sample t-test was used on all sites, species, and size classes when data was available. Due to small sample sizes, statistics were only run on the species by site below: 12

• Bulky Dump: E. variabilis height and circumference and C. oahuense height and total number of woody stems. • Cable House: E. variabilis height and circumference and C. oahuense height and total number of woody stems. • Demo 16: E. variabilis height and circumference and C. oahuense height and total number of woody stems. • Iwa: E. variabilis height and circumference and S. taccada height and circumference.

Survivorship was calculated on all species at each site. Final survivorship was reported as the percentage of alive/dead plants on 26 June 2018. These are reported as “Survivorship of E. variabilis, C. oahuense, and S. taccada by site and size class” (Figure 4) and “Species Survivorship by Site” (Figure 5).

VI) RESULTS Welch t-test

The alternative hypothesis (H1) was rejected in all categories with the exception of S. taccada at Iwa site for the Small (p= 0.0001727) and Medium (p= 0.02918) size classes for height. It is important to note that these statistics evaluated data collected at pre- existing restoration sites rather than data collected from a rigorous experimental design. Refer to Table 2 in the Appendix for a full listing of statistical outputs.

Survivorship Species Survivorship by Site Bulky Dump: goosefoot (50%), sea purslane (20%), bunchgrass (0%), and button sedge (0%). Cable House: bunchgrass (100%), button sedge (90%), peppergrass (80%), and goosefoot (80%). Demo 16: bunchgrass (100%) then goosefoot (40%). Iwa: naupaka (83%) then bunchgrass (56%). Refer to Figure 5: Species Survivorship by Site in the Appendix.

Survivorship of E. variabilis, C. oahuense, and S. taccada by site and size class Bulky goosefoot (Small) (50%) Iwa bunchgrass (Large) (90%) Bulky bunch grass (Unknown size) (0%) Iwa bunchgrass (Medium) (100%) Bulky bunch grass (Small) (0%) Iwa bunchgrass (Small) (70%) Cable goosefoot (Small) (80%) Iwa naupaka (Large) (100%) Cable bunchgrass (Small) (100%) Iwa naupaka (Medium) (100%) Demo goosefoot (Unknown size) (40%) Iwa naupaka (Small) (50%) Demo bunchgrass (Unknown size) (100%)

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Refer to Figure 4: Survivorship of E. variabilis, C. oahuense, and S. taccada by site and size class in the Appendix.

VII) DISCUSSION & RECOMMENDATIONS Community-Level Trends and Recommendations Cable House is located on the north side of Sand island surrounded by windbreaks on three sides giving shelter from the wind and salt spray. The substrate is loose, dry sand making it easier for Bonin petrels to burrow. Cable House consistently has higher temperatures in the afternoon and is crater-shaped. E. variabilis is drought-, wind-, and salt-spray tolerant (Eragrostis variabilis, 2009). F. cymosa and L. bidentatum var. o- waihiense. are drought-, wind-, salt spray-, and heat- tolerant (Fimbristylis cymosa, 2009; Lepidium bidentatum, 2009). All species planted performed well. Recommendations: Plant button sedge, bunchgrass, goosefoot, and peppergrass in small size classes. According to these findings there is no need to invest in fencing nor invest nursury resources to grow out larger size classes.

Bulky Dump is an uncharacterized landfill created by the disposal of scrap metal, used equipment, and unconsolidated waste off the south shore of Sand Island from military activities throughout World War II and the Cold War (A Brief History of Midway Atoll, 2019). The peninsula is approximately 365 meters long by 137 meters (average) wide by 2.75 meters high (U.S. Navy, 1995). It is characterized by high wind and salt spray. Both sea purslane and goosefoot survived with the latter ranking slightly higher. Goosefoot is salt-, wind-, drought-, and heat-tolerant (Chenopodium oahuense, 2009). Sea purslane is tolerant of drought, wind, salt spray, foot traffic, and heat (Sesuvium portulacastrum, 2009). No bunchgrass nor button sedge survived in any size class. Recommendation: Plant sea purslane and goosefoot. More research such as using larger size classes is suggested to improve survival rates of both species. If sensitive species are desired close to the shoreline, consider planting physical buffers like beach naupaka as a screen to reduce stress from heat, salt spray, or a combination. Do not use bunchgrass nor button sedge in the initial stages of restoration.

‘Iwa is a narrow, coastal beach on the south side of Sand island and is adjacent to the active runway. Tall windbreaks are not allowed near Federal Aviation Administration (FAA)- certified airports (FAA Airport Master Record of MDY, 2020). The site experiences high wind and salt spray with accelerated seasonal erosion and deposition. S. taccada is drought-, wind-, salt spray-, and heat- tolerant (Scaevola taccada, 2009). The Welch’s t-test for fencing revealed statistical significance for height for Small and Medium-sized naupaka. Therefore only small and medium naupaka should benefit from fencing. My personal observations at ‘Iwa confirm these findings. Small, unfenced beach naupaka suffered 14 mostly from ripping and shredding from nesting adult seabirds or chicks (Figure 6). Bonin petrels burrowing under fencing were also present at ʻIwa but not at the same density as Cable House. This may have affected survivorship. Recommendations: Save fencing costs by only planting large naupaka and all size classes of bunchgrass.

Demo Site 16 is located on the northeast side of Sand island. The site is more inland with an Ironwood windbreak (C. equisetifolia) therefore wind damage and saltspray are not as much of a stressor (Boland, 2006). All bunchgrass size classes performed well. Goosefoot survival was variable. Recommendations: Plant bunchgrass in small size classes. According to these findings there is no need to invest in fencing nor invest nursury resources to grow out larger size classes. More research is needed to improve goosefoot survival rates.

General Management Recommendations • Nursery Management: Use methods and products to optimize root growth in nursery stock. Hold nursery stock until older plants have a more extensive root system. • In-field Plant Management: Deploy water-retaining gel, slow-release and liquid fertilizers to improve root resiliency in the field to promote survivorship. • Sea purslane performed well at Bulky Dump but was only trialed at this one location. Field observations suggest it is a promising restoration plant particularly for its ability to survive high animal traffic, salt spray, and drought on large seabird colonies. This sprawling species also provides weed suppression to reduce labor and herbicide costs. • Biodegradable fencing or a physical buffer is a natural alternative to traditional plastic fencing. If installed during an outplanting, a biodegradable fence could protect the vulnerable native outplanting from seabird damage, provide nesting material and/or enrichment to seabirds, and provide supplemental nutrients through decomposition.

Future research opportunities 1) Improve statistical power by implementing a scientifically rigorous experimental design. This could include researching paired study sites with similar environmental conditions with larger data sets. 2) Managers could better match plant adaptations to site characteristics. For example, at Bulky Dump consider using salt-tolerant S. portulacastrum in salt spray zones, S. taccada as a wind and salt barrier, and less salt-tolerant C. oahuense farthest from the shoreline. 15

3) Compare plant growth rates to seabird chick growth-development rates to identify when chicks become mobile and begin defoliating native plants. This could optimize fence deployment dates. 16

VIII) ACKNOWLEDGEMENTS

This capstone would not have been possible without the time and collaboration of Dr. Travis Idol, Dr. Linda Cox, Dr. Catherine Chan, Dr. Mehana Vaughan, Dr. Melissa Price, staff and crew of Midway Atoll, and the undying support from my friends and family.

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VIII) REFERENCES A Brief History of Midway Atoll. (2019). Retrieved from https://www.papahanaumokuakea.gov/maritime/midway.html Anderson, W. B., & Polis, G. A. (1999). Nutrient fluxes from water to land: seabirds affect plant nutrient status on Gulf of California islands. Oecologia, 118(3), 324-332. Awkerman, J. A., D. J. Anderson, and G. C. Whittow (2009). Laysan Albatross (Phoebastria immutabilis), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org.eres.library.manoa.hawaii.edu/10.2173/bna.66 Barbier, E. B., Hacker, S. D., Kennedy, C., Koch, E. W., Stier, A. C., & Silliman, B. R. (2011). The value of estuarine and coastal ecosystem services. Ecological monographs, 81(2), 169-193. Boland, D. J., Brooker, M. I. H., Chippendale, G. M., Hall, N., Hyland, B. P. M., Johnston, R. D., & Turner, J. D. (Eds.). (2006). Forest trees of Australia. CSIRO publishing. Broome, S. (2015). Restoration and Management of Coastal Dune Vegetation SoilFacts. Retrieved from https://content.ces.ncsu.edu/restoration-and-management-of- coastal-dune-vegetation Burger J. and Gochfeld M. 1993. Tourism and short-term behavioral responses of nesting masked, red-footed, and blue-footed boobies in the Galapagos. Environ. Conserv. 20: 255–259. Carter, R. W. G. (2013). Coastal environments: an introduction to the physical, ecological, and cultural systems of coastlines. Elsevier. Chapman, V. J. (2016). Coastal vegetation. Elsevier. Chenopodium oahuense. (2009). Retrieved April 9, 2020, from http://nativeplants.hawaii.edu/plant/view/Chenopodium_oahuense Church, J. A. & White, J. W. (2011). Sea level rise from the late 19th to early 21st century. Surv. Geophys. 32, 585–602. Clapp, R. B., & Wirtz, W. O. (1975). The natural history of Lisianski Island, Northwestern Hawaiian Islands. Duarte, C. M., Losada, I. J., Hendriks, I. E., Mazarrasa, I., & Marbà, N. (2013). The role of coastal plant communities for climate change mitigation and adaptation. Nature Climate Change, 3(11), 961. Duffy, D. C. (2010). Changing seabird management in Hawai'i: from exploitation through management to restoration. Waterbirds, 33(2), 193-208. Duvauchelle, D. (2009). Plant fact sheet for aweoweo (Chenopodium oahuense (Meyen) Aellen). USDA Natural Resources Conservation Service, Hawaii Plant Materials Center, Hoolehua, Hawaii 96729. Ellis, J. C. (2005). Marine birds on land: a review of plant biomass, species richness, and community composition in seabird colonies. Plant Ecology, 181(2), 227-241. Eragrostis variabilis. (2009). Retrieved April 12, 2020, from http://nativeplants.hawaii.edu/plant/view/Eragrostis_variabilis FAA Airport Master Record of MDY. (2020). Retrieved April 9, 2020, from https://www.airportiq5010.com/5010web/dashboard/general Fimbristylis cymosa. (2009). Retrieved from http://nativeplants.hawaii.edu/plant/view/Fimbristylis_cymosa 18

Flint, E., & Rehkemper, C. (2002). Control and eradication of the introduced grass, Cenchrus echinatus, at Laysan Island, Central Pacific Ocean. Turning the tide: the eradication of invasive species, 110-115. Flint, E., 2011, Albatross population summary: Hawaiʻian Islands National Wildlife Refuge and Midway Atoll National Wildlife Refuge—annual nest counts through hatch year 2011: Unpublished report for the U.S. Fish and Wildlife Service. Gillham, M. E. (1961). Alteration of the breeding habitat by sea-birds and seals in Western Australia. The Journal of Ecology, 289-300. Global Invasive Species Database. (2018). Species profile: Scaevola sericea. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=1532 on 06-12-2018. Hemer, M. A., Church, J. A. & Hunter, J. R. (2010). Variability and trends in the directional wave climate of the Southern Hemisphere. Int. J. Climatol. 30, 475–491. Holthuijzen, W. (2017). Common Plants of Midway Atoll NWR (2nd ed.). Retrieved from https://www.friendsofmidway.org/ Hyland, B. P. M.; Whiffin, T.; Zich, F. A.; et al. ( 2010). "Factsheet – Scaevola taccada". Australian Tropical Rainforest Plants. Edition 6.1, online version [RFK 6.1]. Cairns, Australia: Commonwealth Scientific and Industrial Research Organisation (CSIRO), through its Division of Plant Industry; the Centre for Australian National Biodiversity Research; the Australian Tropical Herbarium, James Cook University. Retrieved 16 Mar 2013. Izaguirre, C., Méndez, F. J., Menéndez, M., & Losada, I. J. (2011). Global extreme wave height variability based on satellite data: Worldwide Extreme Wave Height. Geophysical Research Letters, 38(10), n/a-n/a. https://doi.org/10.1029/2011GL047302 Joy, R. (2009). Natural Resources Conservation Service. Retrieved from https://www.nrcs.usda.gov/wps/portal/nrcs/detail/pia/plantsanimals/?cid=nrcs1 42p2_037728 Kundzewicz, Z. W., Kanae, S., Seneviratne, S. I., Handmer, J., Nicholls, N., Peduzzi, P., & Muir- Wood, R. (2014). Flood risk and climate change: global and regional perspectives. Hydrological Sciences Journal, 59(1), 1-28. Laidre, K. L., Stirling, I., Lowry, L. F., Wiig, Ø., Heide-Jørgensen, M. P., & Ferguson, S. H. (2008). Quantifying the sensitivity of Arctic marine mammals to climate-induced habitat change. Ecological Applications, 18(sp2), S97-S125. Lepidium bidentatum var. o-waihiense. (2009). Retrieved from http://nativeplants.hawaii.edu/plant/view/Lepidium_bidentatum_o-waihiense Menéndez, M., & Woodworth, P. L. (2010). Changes in extreme high water levels based on a quasi-global tide-gauge data set. Journal of Geophysical Research, 115(C10). https://doi.org/10.1029/2009JC005997 Menéndez, M., Mendez, F. J., Losada, I. J. & Graham, N. E. (2008). Variability of extreme wave heights in the northeast Pacific Ocean based on buoy measurements. Geophys. Res. Lett. 35, L22607 Midway Atoll Conceptual Site Plan. (2008). Retrieved 2020, from https://www.papahanaumokuakea.gov/management/mp.html Moore, J. (2009). A comparative analysis of population estimation methods for a burrow- nesting seabird: a novel ground-count method and closed population capture- recapture modelling. 19

Moreno-Casasola, P. (1986). Sand Movement as a Factor in the Distribution of Plant Communities in a Coastal Dune System. Vegetation, 65(2), 67–76. Mulder, C. P., & Keall, S. N. (2001). Burrowing seabirds and reptiles: impacts on seeds, seedlings and soils in an island forest in New Zealand. Oecologia, 127(3), 350-360. National Oceanic and Atmospheric Administration. (2008). Papahānaumokuākea Marine National Monument Management Plan. Retrieved from https://nmspapahanaumokuakea.blob.core.windows.net/papahanaumokuakea- prod/media/archive/management/mp/vol1_mmp08.pdf NOAA. (2007). Recovery Plan for the Hawaiian Monk Seal. Retrieved from https://www.fisheries.noaa.gov/resource/document/recovery-plan-hawaiian- monk-seal Olson, J. S. (1958). Lake Michigan dune development 2. Plants as agents and tools in geomorphology. The Journal of Geology, 66(4), 345-351. Oppenheimer, M., B.C. Glavovic , J. Hinkel, R. van de Wal, A.K. Magnan, A. Abd-Elgawad, R. Cai, M. Cifuentes-Jara, R.M. DeConto, T. Ghosh, J. Hay, F. Isla, B. Marzeion, B. Meyssignac, and Z. Sebesvari. (2019). Sea Level Rise and Implications for Low-Lying Islands, Coasts and Communities. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N.M. Weyer (eds.)]. In press. Papahānaumokuākea Marine National Monument. (2017). Retrieved from https://www.papahanaumokuakea.gov/ Prescott, A. & Venning, J. (1984). "Aizoaceae". Flora of Australia. 4. Canberra: Australian Government Publishing Service. Preserving the Past - Midway Atoll National Wildlife Refuge and Battle of Midway National Memorial - U.S. Fish and Wildlife Service. (2015). Retrieved from https://www.fws.gov/refuge/Midway_Atoll/Preserving_the_Past.html Pye, K., & Tsoar, H. (2008). Aeolian sand and sand dunes. Springer Science & Business Media. Ranwell, D. S. (1972). Ecology of salt marshes and sand dunes. In Ecology of salt marshes and sand dunes. Chapman and Hall. Reynolds, M. H., Berkowitz, P., Courtot, K. N., & Krause, C. M. (2012). Predicting sea-level rise vulnerability of terrestrial habitat and wildlife of the Northwestern Hawaiian Islands (No. 2012-1182). US Geological Survey. Ricklefs R.E. (1990). Seabird life histories and the marine environment – some speculations. Colonial Waterbirds 13: 1–6. Scaevola taccada. (2009). Retrieved April 12, 2020, from http://nativeplants.hawaii.edu/plant/view/Scaevola_sericea Sesuvium portulacastrum. (2009). Retrieved April 9, 2020, from http://nativeplants.hawaii.edu/plant/view/Sesuvium_portulacastrum Seto, N. W. and D. L. O'Daniel (1999). Bonin Petrel (Pterodroma hypoleuca), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi- org.eres.library.manoa.hawaii.edu/10.2173/bna.385 Shluker, A. (1999). Verbesina encelioides [(Cav.) Bentham & Hooker fil. Ex Gray] ssp. exauriculata [Robinson & Greenman]. HNIS Report for Verbesina encelioides, 12 pp. 20

Short, A. D., & Hesp, P. A. (1982). Wave, beach and dune interactions in southeastern Australia. Marine geology, 48(3-4), 259-284. Solomon, S., Manning, M., Marquis, M., & Qin, D. (2007). Climate change 2007-the physical science basis: Working group I contribution to the fourth assessment report of the IPCC (Vol. 4). Cambridge university press. Starr, K., & Starr, F. (2008). Botanical Survey Of Midway Atoll. Retrieved from http://www.starrenvironmental.com/ Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M. M. B., Allen, S. K., Boschung, J., Midgley, P. M. (2013). Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, 14. Tutorials for learning R. (2017). Retrieved from https://www.r-bloggers.com/how-to- learn-r-2/ U.S. Navy. 1995. Technical Memorandum for Evaluation of Remedial Alternatives Naval Air Force (NAF) Midway Island. Ogden Environmental and Energy Services Co., Inc. Comprehensive Long-Term Environmental Action Navy (CLEAN) Contract No. N62742-90-D-0019 Cto No. 0136. Vermeer, M., & Rahmstorf, S. (2009). Global sea level linked to global temperature. Proceedings of the National Academy of Sciences, 106(51), 21527–21532. https://doi.org/10.1073/pnas.0907765106 Vidal, E., Jouventin, P., & Frenot, Y. (2003). Contribution of alien and indigenous species to plant-community assemblages near penguin rookeries at Crozet archipelago. Polar Biology, 26(7), 432-437. Warham, J. (1990). The petrels: their ecology and breeding systems. A&C Black. Welcome to the Pacific Region - U.S. Fish and Wildlife Service. (2018). Retrieved from https://www.fws.gov/pacific/ Western Australian Herbarium (1998). FloraBase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions.https://florabase.dpaw.wa.gov.au/ Wilkinson, K. M., Landis, T. D., Haase, D. L., Daley, B. F., & Dumroese, R. K. (2014). Tropical nursery manual: a guide to starting and operating a nursery for native and traditional plants. Agriculture Handbook 732. Washington, DC: US Department of Agriculture, Forest Service. 376 p., 732. Young, I. R., Zieger, S., & Babanin, A. V. (2011). Global Trends in Wind Speed and Wave Height. Science, 332(6028), 451–455. https://doi.org/10.1126/science.1197219

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IX) APPENDIX

Figure 1: Bonin petrels (P. hypoleuca) burrow into soil, generally under vegetation such as native bunchgrass (E. variabilis). The roots of native plant species typically provide better substrate stability than non-natives. As a result, fencing entrapment may occur as the bird exits its burrow.

Figure 2: Native plants evaluated within this study; a) E. variabilis, b) S. taccada, c) C. oahuense, d) S. portulacastrum, e) F. cymosa, and f) L. bidentatum. All are species used across the Hawaiian archipelago for coastal restoration. 22

Figure 3: The four restoration sites across Sand island evaluated within this study; a) Bulky Dump, b) Cable House, c) Demo Site 16, and d) Iwa. Cable House and Demo Site 16 are located on the north side of the island with physical buffers that reduce wind and salt spray. Iwa and Bulky Dump are located on the southside of the island with strong winds and salt spray. Both are coastal sites and adjacent to the active runway.

Figure 4: Survivorship results of E. variabilis, S. taccada, and C. oahuense by site and size reported as percentages. These species had the largest sample sizes with multiple size classes and/or were across multiple sites. Final survivorship percentage was recorded on 21 June 2018. 23

Figure 5: Total survivorship results by site and by species reported as percentages. Species include E. variabilis, S. taccada, C. oahuense, S. portulacastrum, F. cymosa, and L. bidentatum. Final survivorship percentage was recorded on 21 June 2018.

Figure 6: Seabird-induced damage varies depending on the plant morphology. a) A juvenile chick roughly two months old near a medium sized E. variabilis at Iwa when chicks are becoming interested in ripping and shredding. Its stems are clipped to the crown however the roots are still intact and may recover (photo taken 8 March 2018). b) Circus stake at Iwa where a small, unfenced S. taccada was located, its death was most likely due to bird damage.

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Table 1: Complete plant inventory for this evaluation. It is important to note that there is an equal number of plants per category and per fenced versus unfenced. Small sample sizes limited statistical power therefore a Welch’s two sample t-test was run exclusively on E. variabilis, S. taccada, and C. oahuense with the largest sample sizes.

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Table 2: Complete list of all Welch’s two sample t-test values generated by site and species- appropriate measurements such as height, circumference, and total number of woody stems (p < 0.05). Of all values generated, Small (p = 0.0001727) and Medium (p = 0.02918) sized S. taccada at Iwa were statistically significant for height.