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Removal of Nonnative Vines and Post-Hurricane Recruitment in Tropical Hardwood Forests of Florida
BRB
Available Online

Horvitz, Carol C.

,

Koop, Anthony

2001
In hardwood subtropical forests of southern Florida, nonnative vines have been hypothesized to be detrimental, as many species form dense ‘‘vine blankets’’ that shroud the forest. To investigate the effects of nonnative vines in post-hurricane regeneration, we set up four large (two pairs of 30 3 60 m) study areas in each of three study sites. One of each pair was unmanaged and the other was managed by removal of nonnative plants, predominantly vines.Within these areas, we sampled vegetation in 5 3 5 m plots for stems 2 cm DBH (diameter at breast height) or greater and in 2 3 0.5 m plots for stems of all sizes. For five years, at annual censuses, we tagged and measured stems of vines, trees, shrubs and herbs in these plots. For each 5 3 5 m plot, we estimated percent coverage by individual vine species, using native and nonnative vines as classes. We investigated the hypotheses that: (1) plot coverage, occurrence and recruitment of nonnative vines were greater than that of native vines in unmanaged plots; (2) the anagement program was effective at reducing cover by nonnative vines; and (3) reduction of cover by nonnative vines improved recruitment of seedlings and saplings of native trees, shrubs, and herbs. In unmanaged plots, nonnative vines recruited more seedlings and had a significantly higher plot-cover index, but not a higher frequency of occurrence. Management significantly reduced cover by nonnative vines and had a significant overall positive effect on recruitment of seedlings and saplings of native trees, shrubs and herbs. Management also affected the seedling community (which included vines, trees, shrubs, and herbs) in some unanticipated ways, favoring early successional species for a longer period of time. The vine species with the greatest potential to ‘‘strangle’’ gaps were those that rapidly formed dense cover, had shade tolerant seedling recruitment, and were animal-dispersed. This suite of traits was more common in the nonnative vines than in the native vines. Our results suggest that some vines may alter the spatiotemporal pattern of recruitment sites in a forest ecosystem following a natural disturbance by creating many very shady spots very quickly.
A systematic review of human and animal leptospirosis in the Pacific Islands reveals pathogen and reservoir diversity
BRB
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Benschop, Jackie

,

Goarant, Cyrille

,

Guernier, Vanina

,

Lau, Colleen L.

Background: The Pacific Islands have environmental conditions highly favourable for transmission of leptospirosis, a neglected zoonosis with highest incidence in the tropics, and Oceania in particular. Recent reports confirm the emergence and outbreaks of leptospirosis in the Pacific Islands, but the epidemiology and drivers of transmission of human and animal leptospirosis are poorly documented, especially in the more isolated and less developed islands.Methodology/Principal findings:We conducted a systematic review of human and animal leptospirosis within 25 Pacific Islands (PIs) in Polynesia, Melanesia, Micronesia, as well as Easter Island and Hawaii. We performed a literature search using four international databases for articles published between January 1947 and June 2017. We further included grey literature available on the internet. We identified 148 studies describing leptospirosis epidemiology, but the number of studies varied significantly between PIs. No data were available from four PIs. Human leptspirosis has been reported from 13 PIs, with 63% of all studies conducted in Hawaii, French Polynesia and New Caledonia. Animal leptospirosis has been investigated in 19 PIs and from 14 host species, mainly pigs (18% of studies), cattle (16%) and dogs (11%). Only 13 studies provided information on both human and animal leptospirosis from the same location. Serology results were highly diverse in the region, both in humans and animals. Conclusions/Significance: Our study suggests that, as in other tropical regions, leptospirosis is widespread in the PIs while showing some epidemiological heterogeneity. Data are scarce or absent from many PIs. Rodents, cattle, pigs and dogs are all likely to be important carriers, but the relative importance of each animal species in human infection needs to be clarified. Epidemiological surveys with appropriate sampling design, pathogen typing and data analysis are needed to improve our understanding of transmission patterns and to develop effective intrevention strategies.
The red vented-bulbul (Pycnonotus cafer): invasion dynamics and ecological impacts of an introduced pest bird in New Caledonia and implications for management
BRB
Available Online

Martin Thibault

2018
Suite à la soutenance de thèse effectuée en juillet 2018 à l’Université de Massey, le manuscrit de Martin Thibault, intitulé « Le bulbul à ventre rouge (Pycnonotus cafer): dynamique d’invasion et impacts écologiques d’un oiseau introduit en Nouvelle Calédonie. Invasive alien species are a major cause of biodiversity loss globally, especially on islands where high species richness and levels of endemism accentuate their impacts. Various international institutions have constructed lists of the most harmful invasive species to help environment managers at both global and local scales to prioritize their efforts. The red-vented bulbul (Pycnonotus cafer) is a passerine bird species considered among the three worst invasive birds on the planet. This species is currently spreading over the tropical archipelago of New Caledonia, one of the 36 world biodiversity hotspots. This dissertation presents the findings of a PhD study conducted in New Caledonia with two objectives: 1) to describe this introduced population, and 2) to evaluate the threats from its dispersal using both existing knowledge and new in-situ and ex-situ data and a variety of analysis techniques. From the literature, I identified three key impacts explaining the species’ status: i) damage to agricultural crops, ii) noxious seed dispersal, and iii) competition with other avifauna. I estimated the local population size (approx. 140,000 individuals), its habitat use (inhabited areas), its density along an urbanization gradient (30-120 ind/km2), and I produced lists of consumed plant and animal species and identified a colour preference in the foraging strategy of the red-vented bulbul. Exploration of each impact category revealed i) substantial losses on fruit production (18% of tomato production), ii) impact on the abundance of nine native bird species that may be driving a spatial reassembly of the community, and iii) a short distance dispersal (77-92 m) that could promote the dispersal of introduced plant species at the expense of endemic species. Finally, through modelling, I estimated the climatic niche of the species at a global scale and identified that most island territories as suitable for the establishment of this invasive bird species. Regardless of whether the red-vented bulbul deserves its status as “world worst” species, quantitative impact assessments in its alien range such as the studies presented here are needed to prevent the dispersal and harmful impacts of this species on human activities and sensitive ecosystems. Implications for management are discussed.
Global evidence that deforestation amplifies flood risk and severity in the developing world
BRB
Available Online

Bradshaw, Corey J. A.

,

Brook, Barry W.

,

Peh, Kelvin S. H.

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Sodhi, Navjot S.

2007
With the wide acceptance of forest?protection policies in the developing world comes a requirement for clear demonstrations of how deforestation may erode human well?being and economies. For centuries, it has been believed that forests provide protection against flooding. However, such claims have given rise to a heated polemic, and broad?scale quantitative evidence of the possible role of forests in flood protection has not been forthcoming. Using data collected from 1990 to 2000 from 56 developing countries, we show using generalized linear and mixed?effects models contrasted with information?theoretic measures of parsimony that flood frequency is negatively correlated with the amount of remaining natural forest and positively correlated with natural forest area loss (after controlling for rainfall, slope and degraded landscape area). The most parsimonious models accounted for over 65% of the variation in flood frequency, of which nearly 14% was due to forest cover variables alone. During the decade investigated, nearly 100?000 people were killed and 320 million people were displaced by floods, with total reported economic damages exceeding US$1151 billion. Extracted measures of flood severity (flood duration, people killed and displaced, and total damage) showed some weaker, albeit detectable correlations to natural forest cover and loss. Based on an arbitrary decrease in natural forest area of 10%, the model?averaged prediction of flood frequency increased between 4% and 28% among the countries modeled. Using the same hypothetical decline in natural forest area resulted in a 4–8% increase in total flood duration. These correlations suggest that global?scale patterns in mean forest trends across countries are meaningful with respect to flood dynamics. Unabated loss of forests may increase or exacerbate the number of flood?related disasters, negatively impact millions of poor people, and inflict trillions of dollars in damage in disadvantaged economies over the coming decades. This first global?scale empirical demonstration that forests are correlated with flood risk and severity in developing countries reinforces the imperative for large?scale forest protection to protect human welfare, and suggests that reforestation may help to reduce the frequency and severity of flood?related catastrophes.
Recruitment dynamics of invasive species in rainforest habitats following Cyclone Larry
BRB
Available Online

Bradford, M.J.

,

Ford, A.F.

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Galway, K.E.

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Metcalfe, D.J.

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Murphy, H.T.

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Sydes, T.A.

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Westcott, D.J.

2008
In tropical forests, natural disturbance creates opportunities for species to claim previously utilized space and resources and is considered an important mechanism in the maintenance of species diversity. However, ecologists have long recognized that disturbance also promotes exotic plant invasions. Cyclones cause extensive defoliation, loss of major branches and multiple tree falls, resulting in a significantly more open canopy and increased light and heat levels in the understorey. The widespread and massive disturbance caused by cyclones provides ideal conditions for rapid recruitment and spread of invasive species. The ecological roles of invasive species in rainforest habitats following such a severe disturbance are poorly understood. Severe category 4 Cyclone Larry crossed the North Queensland coast in March 2006 causing massive disturbance to rainforest habitats from Tully to Cairns and west to the Atherton Tablelands. We established 10 plots in an area extensively damaged by this cyclone near El Arish in North Queensland. On each plot nine 2×2 m quadrats were established with three quadrats per plot in each of the following treatments: (i) complete debris removal down to the soil layer, (ii) removal of coarse woody debris only, and (iii) uncleared. We monitored recruitment, growth and mortality of all native and invasive species in the 90 quadrats every 3 months since the cyclone. Here we present the recruitment dynamics of invasive species across the study area in relation to the level of disturbance, the type of quadrat treatment, and the diversity and abundance of the native recruiting flora over the first 12 months post?cyclone. Our results suggest that invasive species will mostly comprise a transient component of the flora in the early stages of the successional response. However, some species may have longer?term effects on the successional trajectory of the rainforest and future forest composition and structure.