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Wildfire is a major threat to natural resources and native species in Hawai‘i, but the frequency and extent of wildfires across the archipelago has not been well quantified. Our objective was to summarize the available wildfire data for Hawai‘i and synthesize the social and ecological dimensions of wildfire drivers, impacts, and management responses. We constructed a 110-yr span of wildfire records for the state of Hawai‘i to examine historical trends (1904–2011) and summarized relationships between contemporary wildfire occurrence (2005–2011) and land use/land cover types and human population. Total area burned statewide increased more than fourfold from 1904 to 1959 to peaks in the 1960s–1970s and mid-1990s to present. From 2005 to 2011, on average, 1,007 wildfires were reported across the state per year (±77 SE), burning an average of 8,427 ha yr-1 (±2,394 SE). Most fires (95%) were <4 ha, while most area burned (93%) was attributed to fires ≥40 ha. Ignition frequency was positively correlated with human population across islands. Wildfires were most frequent in developed areas, but most areas burned occurred in dry nonnative grasslands and shrublands that currently compose 24% of Hawai‘i’s total land cover. These grass-dominated landscapes allow wildfires to propagate rapidly from areas of high ignition frequencies into the forested margins of the state's watersheds, placing native habitat, watershed integrity, and human safety at risk. There is an urgent need to better assess fire risk and impacts at landscape scales and increase the integration of prefire planning and prevention into existing land management goals.
The eradication of dominant, nonnative trees can alter soil conditions in forest ecosystems by changing the forest's water balance. To test this idea, we measured water in surface soil in forests dominated by an invasive nonnative tree (Casuarina equisetifolia Forst.) on Nishijima Island, a subtropical island in the Ogasawara Islands group, northwestern Pacific Ocean. The volumetric water content of surface soils at sites where all trees of C. equisetifolia were killed by herbicide was compared with adjacent invaded control sites, and effects of time since tree removal (up to 3 yr) were assessed. Dry weights of accumulated litter, total canopy openness of the forest canopy, maximum heights, and total plant cover of herbaceous vegetation were also compared between treatment and control plots. Volumetric soil water content in quadrats where C. equisetifolia trees were removed (removal area) was significantly higher than at control quadrats. We found that the effect of C. equisetifolia removal on soil water content slightly decreased 3 yr after removal. In addition, the dry weights of accumulated litter in removal quadrats decreased with time after removal, and maximum heights and total plant cover increased. We observed higher values of total canopy openness at removal sites regardless of time after removal. These results suggested that the death of these dominant, nonnative trees could increase the available water in soils of invaded forests, and that increases may be related to changes in the water balance of the ecosystem, which can in turn affect restoration of forest ecosystems.
Climate change has resulted in the geographic and vertical expansion of oxygen minimum zones but their impact on the vertical distribution of commercially important species, such as tunas, is not well understood. Although La Niña events are characterized by increased upwelling along the equator, the increased primary productivity and bacterial proliferation drive the expansion of oxygen minimum zones. Vertical habitat of four tropical tuna species were characterized using direct observations of the oceanographic conditions of the Central Pacific Ocean during the 2008 La Niña event and existing primary literature on temperature and dissolved oxygen physiological tolerances for these tunas. Concentrations of potential prey were estimated using Acoustic Doppler Current Profiler raw backscatter and surface zooplankton tows. Based on the oceanographic conditions observed from February to June, low dissolved oxygen levels, more so than low temperatures, were inferred to restrict the predicted vertical habitat of four commercially important tuna species (bigeye, yellowfin, skipjack, and albacore). During peak La Niña conditions, temperature and dissolved oxygen tolerance limits of all four tuna species were reached at approximately 200m. Zooplankton and myctophid fish densities peaked in the upper 200m between 0° N and 5° N, which corresponded to a region with a shallow thermocline (150 m). Our findings suggest the possibility that competition and susceptibility to surface fishing gears may be increased for tropical tunas during a strong La Niña event due to vertical habitat restrictions.
Blue whales are infrequently reported from New Zealand and their taxonomic status is unclear. Here we present new information on the residency, external morphology, and habitat use of blue whales encountered in New Zealand waters. Thirty-one blue whales were photo-identified around the North and South Islands of New Zealand from 2004 to 2014 in seven different months of the year. One photographic match was found between June 2011 and March 2013: the first evidence that an individual blue whale has remained in or returned to New Zealand waters in different years and seasons. Observations of the external morphology of blue whales encountered off the South Island confirm that there is a shorter, non-Antarctic form of blue whale occurring near New Zealand. Body length and proportion, head shape, body condition, and skin condition were similar to Australian but not Antarctic blue whales. In 2013, feeding behavior was observed off the South Island's west coast and strong evidence of feeding was observed off the east coast and is the first reported occurrence of feeding for these locations. Feeding behavior was also observed in the Hauraki Gulf in November 2010. Feeding in these widely spread locations, in addition to the recently reported foraging ground in the South Taranaki Bight, suggest that New Zealand coastal waters are a feeding area for blue whales.
Sponges are functionally important coral reef fauna and there is strong evidence from the Caribbean that predation has important impacts on sponge-assemblage dynamics; whether the same is true for Indo-Pacific sponges remains unknown. As a first step toward understanding the potential effects of spongivores on sponge diversity and abundance, we identified sponge predators at nine sites in Wakatobi Marine National Park, Indonesia, and conducted a short-term caging experiment to examine the effects of excluding predators on noncryptic reef sponges at this location. Nudibranchs were the most abundant invertebrate spongivores, although their low densities are likely to limit their influence on sponges. Fish were the most abundant vertebrate spongivores with 16 species from six families observed feeding on sponges. Based on their abundance and our feeding observations, the fish with the greatest potential to influence sponge assemblages in Wakatobi Marine National Park were Zanclus cornutus, Chaetodon kleinii, Pygoplites diacanthus, and Pomacanthus sexstriatus. We did not detect an effect of excluding spongivores on noncryptic reef sponge abundance in our caging experiment, which may be due to these species having evolved chemical defenses against predators. Important areas for further research include the chemical ecology of Indo-Pacific sponges and whether spongivory currently restricts some species to cryptic or nonreef habitats.
The grapsoid and gall crab fauna of Easter Island is reviewed, based on historical records and material collected by the Science Museum of Long Island Easter Island Expedition of 1998–1999. Previously, nine grapsoids identified to the species level, but no gall crabs, were recorded from the island. The present work reports on eight species of grapsoids: Pachygrapsus laevimanusStimpson, 1858 (previously recorded from the island as Pachygrapsus transversus [Gibbes, 1850]); Pachygrapsus plicatus (H. Milne Edwards, 1837) (new record); Leptograpsus variegatus (Fabricius, 1793); Cyclograpsus longipesStimpson, 1858; Ptychognathus easteranusRathbun, 1907; Percnon pascuensisRetamal, 2002 (redescribed and figured); Guinusia dentipes (De Haan, 1835); and Guinusia integripes (Garth, 1973) (new combination). Geograpsus crinipes (Dana, 1851) and Guinusia chabrus (Linnaeus, 1758) have been previously recorded from the island; no material of the former was collected and the latter is considered an erroneous identification of Guinusia dentipes. Dacryomaia japonica (Takeda & Tamura, 1981) is the first identified gall crab from the island. Color notes for six species and illustrations for several important morphological characters of Percnon pascuensis are provided.
Here we report on two new reef fish species from the remote and isolated Easter Island—the striped boarfish Evistias acutirostris and the ornate butterflyfish Chaetodon ornatissimus were observed during scuba dives and underwater video around Easter Island, as well as at nearby Apolo Seamount. These observations are the first records of these species for the southeastern Pacific, which represents a major extension to their distributions and raises questions about the origins and persistence of reef fishes in remote subtropical locations.
Archaeological excavations on Tiga provide the first vouchered herpetological records for this small island between Lifou and Maré in the Loyalty Islands. Eighty-three skeletal elements from four sites yielded material assignable to skinks (Emoia loyaltiensis, Lioscincus nigrofasciolatus), geckos (Bavayia crass i-collis, B. sp., Gehyra georgpotthasti, Nactus pelagicus), and a boid snake (Candoia bihroni) all known from elsewhere in the Loyalties, as well as undetermined material consistent with these and other Loyalties lizards. Diagnostic features of geckos versus skinks for elements commonly recovered from archaeological sites and from owl pellets are discussed. Gehyra georgpotthasti has a limited distribution in the Loyalties and its occurrence on Tiga clarifies its range. The boid snake is the only reptile likely to have been harvested by human inhabitants of Tiga. The presence of gekkonid geckos in pre-European times is confirmed and contrasts with the situation of Grande Terre fossil sites, where only diplodactylid geckos have been recovered. Although it is anticipated that all species recovered from archaeological sites are still present on the island, a modern herpetofaunal survey is needed.
The island of Kaua‘i, Hawai‘i has several remaining populations of endangered, endemic Hawaiian petrels (Pterodroma sandwichensis) and Newell's shearwaters (Puffinus newelli) that would be threatened by the presence of predatory mongooses (Herpestes javanicus). Despite over 200 putative sightings, 1 road-kill and 2 recent captures, it is not clear if mongooses have actually become established on Kaua‘i. Comparing road transects on three Hawaiian islands, we found mongooses present on O‘ahu and Maui where they are known to occur and no evidence of significant populations on Kaua‘i. Three population scenarios are presented that would account for the three specimens, the past sightings, and the absence of sightings on our transects on Kaua‘i.