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Global evidence that deforestation amplifies flood risk and severity in the developing world
BRB
Available Online

Bradshaw, Corey J. A.

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Brook, Barry W.

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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.

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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.
ECOLOGIE ET IMPACTS D’UN PREDATEUR INTRODUIT AU SEIN D’UN HOT-SPOT MONDIAL DE BIODIVERSITE - LE CHAT HARET FELIS CATUS DANS L’ARCHIPEL NEO-CALEDONIEN
BRB
Available Online

Pauline Palmas

Le chat haret est l’un des prédateurs invasifs les plus dommageables pour la biodiversité insulaire. Sa présence est associée à une perte de biodiversité sur l’ensemble des îles sur lesquelles il est établi, et où il constitue une menace pour de nombreuses espèces de vertébrés souvent endémiques et menacés. En Nouvelle-Calédoniedes populations de chats harets sont présentes dans tous les milieux et habitats et l’étude de son écologie et de ses impacts sur la faune ont fait l’objet de ce travail de thèse. L’analyse du régime alimentaire sur 14 sites d’études représentatifs des 4 habitats majeurs a révélé un régime très diversifié et une forte prédation sur les vertébrés natifs et notamment sur le groupe des scinques, des roussettes et des pétrels. Parmi les 44 espèces de vertébrés retrouvées dans le régime alimentaire de ce prédateur invasif, la plupart sont endémiques et 20 sont listées comme menacées sur la liste rouge mondiale de l’UICN. Le suivi des déplacements d’une dizaine d’individus équipés de colliers GPS au niveau d’une presqu’île de la côte ouest abritant une importante colonie d’oiseaux marins, a permis de mettre en évidence de grands domaines vitaux pour les mâles, des domaines vitaux petits pour les femelles et des patrons de déplacements importants liés aux différentes étapes du cycle reproducteur des oiseaux marins. Ces éléments, couplés aux analyses de régime alimentaire suggèrent une prédation à la fois sur les adultes reproducteurs mais également sur les jeunes oiseaux proches de l’envol, et ceci à une large échelle géographique puisque certains des chats harets concernés avaient le coeur de leur domaine vital situé à plus de 3km de la colonie. Une opération expérimentale de contrôle d’une population de chats harets a été conduite sur cette presqu’île et a montré une faible durabilité des effets de la suppression des individus sur les densités observées et une rapide recolonisation du site. Les résultats de ce travail plaident pour la mise en place de mesures de limitation des impacts occasionnés et permettent en particulier de cibler les habitats de maquis et forêt humide comme prioritaires en matière de limitation des abondances. Ces travaux nous éclairent également sur l’emprise spatiale et l’intensité des futures mesures de contrôle à conduire dans le contexte d’îles de grande superficie et fortement envahies.