Sediment core studies from Saipan suggest that fires did not play a prominent role in the disturbance regime of the Mariana Islands and have increased in frequency since human settlement around 4,000 years ago. On Saipan fires are understood to interrupt the pattern of succession leading to the degradation of native limestone forests, the proliferation of grasslands and the eventual creation of badlands. Little baseline data regarding the spatial and temporal patterns of fire on Saipan exist to create effective Fire Management Plans. This project uses Landsat 8 images from April 2013 to July 2020 and the Normalized Burn Ratio to identify historic fires to evaluate patterns that will inform on effective fire management policies. Over the study period we detected 1,608 ha of burnt land, in four specific hotspots. Of the area burned, 40% were in grasslands, 31% in evergreen forests, and 21% in scrub-shrub. 41% of all hectares that burned more than once throughout the study period were grasslands, indicating that this was the landcover type most vulnerable to repeat burn events. We also found a strong seasonal trend, with the average amount of burnt land detected in the dry season 280% higher than the average amount of burnt land detected in the wet season. Finally, both total precipitation and the absence of precipitation were highly correlated to the amount of burn area identified (P < .05). The information elucidated through this study will be used by local agencies to implement management plans geared toward controlling wildfires.

The Hawaiian Islands have long been seen as relatively devoid of native toxic plant species, a result of the paucity of herbivorous predators in this biogeographically isolated archipelago. This assertion has been subjective, without quantitative comparison to floras that evolved in the presence of such predators. We test this assertion by comparing the richness of toxic species in the native flora of the main Hawaiian Islands to that in the naturalized flora of these islands. That test shows the assertion to be correct: the relative abundance of toxic plant species in the naturalized Hawaiian flora is nearly ten times greater than the relative abundance of those species in the Hawaiian native flora. Of the approximately 150 toxic plant species now found in these islands, 92% are naturalized. The species richness of both native and naturalized Hawaiian plant species correlates positively with island size, as does the richness of toxic native and toxic naturalized plant species. These results, and the lack of significant residuals in species–area relationships across the main Hawaiian Islands, suggest that the relative youth of Hawai‘i Island is not needed to account for native plant species richness on this island.

The White Tern (Gygis alba) is a common seabird that nests on islands in tropical and subtropical oceans. In the southeastern Hawaiian Islands, White Terns breed only in urban and suburban areas of Honolulu. The Honolulu population has grown from a single pair in 1961 to 2,300 birds in 2016. We measured breeding success of White Terns in Honolulu and examined aspects of their breeding biology and the environment that may affect breeding. We documented 3,855 breeding events in Honolulu from 2016 to 2019. Breeding success was 68.3% and varied less than 3% among years. Breeding occurred in all months, with lowest activity in the summer and a peak in the winter and spring, but the pattern varied among years. White Terns bred in 64 tree species. Breeding success varied among tree species and was related to characteristics of the trees and their attractiveness to non-native predators. The height of breeding events was 9.26 ± 0.05 m and success was related to height, with higher success in events 5–10 m above ground. The diameter of branches on which breeding occurred was 10.2 ± 0.1 cm and success was related to branch diameter, with lower success on branches >20 cm. The high breeding success of White Terns in Honolulu is related to: the small size and isolation of the O‘ahu population, which may result in reduced intra-specific competition for food; protection from predators provided by the urban environment; and trimming of trees by arborists, which unintentionally improves the value of trees as breeding sites for terns.

Soil erosion has been recognized as a significant environmental issue in the United States for over 200 years. Numerous attempts have been made to predict and quantify the phenomenon, yet significant issues remain that hinder the accuracy and effectiveness of such models. This article describes the application of the new generation Unit Stream Power Erosion and Deposition (USPED) model that estimates soil erosion and concomitant sediment deposition at Schofield Barracks, Hawai‘i, an active Army training installation. The model accurately placed modeled estimates of soil erosion and sediment deposition in the correct visually determined category 85% the time (51 of 60 randomly assigned points). While not perfect, the USPED model estimates exceeded a predetermined accuracy threshold of 80%, recognizing that model estimates represent long-term estimates while visual estimates are based primarily on relatively recent conditions.

Understanding the behavior of birds around tall structures such as electrical-transmission lines, communication towers, and wind turbines is important in assessing the potential effects of those structures on bird populations; it is especially important for threatened or endangered species. We studied responses of the mostly crepuscular/nocturnal Hawaiian Petrel (Pterodroma sandwichensis) and the mostly nocturnal Newell's (Townsend's) Shearwater (Puffinus newelli; Aves: Procellariiformes) to coastal and near-coastal transmission lines on Kaua‘i Island, Hawai‘i, USA, in 1992–2002. Hawaiian Petrels responded to transmission lines significantly more often (19.1% of the time; N = 209) than Newell’s Shearwaters did (7.4%; N = 392), responded significantly more often with decreasing distance from a line, and responded significantly less often if a study-site was dark (i.e., unlit by ambient lights from nearby towns) than if it was light (i.e., lit by ambient lights from nearby towns), regardless of whether the sky was light (i.e., daylight or crepuscular light conditions) or dark (nocturnal light conditions). In contrast, Newell’s Shearwaters showed little variation in response rates by distance or by whether the study-site or sky was light or dark. Hawaiian Petrels mostly responded to transmission lines by changing flight velocity and flight altitude, whereas Newell’s Shearwaters mostly responded by changing flight direction and flight altitude. The higher response rates and more-buoyant flight characteristics of Hawaiian Petrels than Newell’s Shearwaters may contribute to lower rates of fatality of Hawaiian Petrels than Newell’s Shearwaters at coastal and near-coastal transmission lines on Kaua‘i.

The integument of marine mammals provides an ideal substrate for colonization by photosynthetic epizoans. A review of the literature and new data from the harbor seal (Phoca vitulina richardsi) revealed at least eight genera of photosynthetic cyanobacteria and algae colonizing the pelage of six species of pinnipeds. The relationship may be considered a facultative association, beneficial to the photosynthetic epizoans and relatively neutral (but perhaps slightly costly) to their mammalian hosts. We studied the incidence of algal growth on the pelage of harbor seals in central California during 1985–1987 and 2017. The green alga Ulva sp. occurred on adult females throughout the year and rarely occurred on adult males. Algal growth appeared to be most frequent during the breeding season (February to May) and least frequent during the molt and post-molt seasons (June to October). Algal growth occurred more frequently on harbor seals in estuaries than along the coast. Much remains to be learned about the colonization of pinnipeds by photosynthetic epizoans and why some seals are more susceptible to colonization by algae than others.

Globally, coral reefs have been in significant decline for several decades. In contrast, the reefs in Kāne‘ohe Bay, Hawai‘i have presented an opposite trend during the same period, showing recovery and resilience even while experiencing significant disturbances. Since the diversion of sewage outfalls from southern Kāne‘ohe Bay in the late 1970s, coral populations have made a gradual recovery despite periodic mortality from heat-induced coral bleaching, competition from native and invasive algae, and freshwater inundation during heavy rainfall events. This study repeated surveys originally performed in 2000 for the free-living, solitary, common mushroom coral Lobactis (Fungia) scutaria to investigate population stability and size structure in the north, central, and south regions of the Bay. We found significant increases of up to 538% in the density of L. scutaria in Kāne‘ohe Bay between 2000 and 2018. An increased abundance of sexual recruits was particularly noteworthy. In 2018, the population structure reflected 9.2% sexual recruits and 3.8% asexual buds compared to 2000 when sexual recruits were nearly absent (0.4% of population.) We also found a positive linear relationship between sexual recruit density and adult density. Sites on patch reefs under management actions that involved the physical removal of invasive algae and sea urchin out-planting to crop the algae showed no difference in mushroom coral densities from control sites. While the growing population of mushroom corals in Kāne‘ohe Bay, Hawai‘i provides an exemplar species for resilience and recovery, it is unclear if this short-term expansion will continue under future conditions.