Les effectifs d’oiseaux de mer ont chuté de plus de 60 % depuis soixante ans

Fou varié (Sula variegata) mort, visiblement en état d'inanition, sur la plage Lobos marinos, à 127 km au sud de Lima, au Pérou. Mai 2012. Ph.: Pierre-Olivier Combelles. http://pocombelles.over-blog.com/article-les-oiseaux-meurent-au-perou-105025096.html

Information de Reporterre:

http://www.reporterre.net/spip.php?page=redirect&id_article=7883

La planète compte 200 millions d’oiseaux de mer en moins. C’est ce que révèle une recherche universitaire publiée dans la revue scientifique PlosOne.

Les chercheurs du projet « Sea around us » se sont penchés sur plus de 300 espèces, qui constituent environ 20 % des populations totales d’oiseaux marins. D’après eux, cet échantillon est « représentatif » car les données ont été récoltées sur différents sites côtiers à travers le monde. Les conclusions sont implacables : 69,7 % des effectifs d’oiseaux marins auraient disparu sur une période de 60 ans, entre 1950 et 2010.

 Source (en anglais) : Sea around us

Population Trend of the World’s Monitored Seabirds, 1950-2010

Michelle Paleczny ,Edd Hammill , Vasiliki Karpouzi, Daniel Pauly.

PLOS. Published: June 9, 2015
DOI: 10.1371/journal.pone.0129342.

Abstract

"Seabird population changes are good indicators of long-term and large-scale change in marine ecosystems, and important because of their many impacts on marine ecosystems. We assessed the population trend of the world’s monitored seabirds (1950–2010) by compiling a global database of seabird population size records and applying multivariate autoregressive state-space (MARSS) modeling to estimate the overall population trend of the portion of the population with sufficient data (i.e., at least five records). This monitored population represented approximately 19% of the global seabird population. We found the monitored portion of the global seabird population to have declined overall by 69.7% between 1950 and 2010. This declining trend may reflect the global seabird population trend, given the large and apparently representative sample. Furthermore, the largest declines were observed in families containing wide-ranging pelagic species, suggesting that pan-global populations may be more at risk than shorter-ranging coastal populations."

Introduction

Human activities such as fisheries and pollution are threatening the world’s marine ecosystems [1], causing changes to species abundance and distribution that alter ecosystem structure, function and resilience [2–4]. In response, increasing numbers of marine biologists and managers seek to achieve management measures allowing the persistence of healthy, productive and resilient ecosystems [5]. Such ecosystem-based management requires better understanding of ecosystems pre-disturbance, as baselines of harvested and/or otherwise impacted species such as fish, marine mammals, and seabirds have shifted from their historical levels [6–9].

Seabird population changes are good indicators of long-term and large-scale change in marine ecosystems because seabird populations are relatively well-monitored, their ecology allows them to integrate long-term and large-scale signals (they are long-lived, wide-ranging and forage at high trophic levels) [10–11], and their populations are strongly influenced by threats to marine and coastal ecosystems. These threats include entanglement in fishing gear, overfishing of food sources, climate change, pollution, disturbance, direct exploitation, development, energy production, and introduced species (predators such as rats and cats introduced to breeding islands that were historically free of land-based predators) [12]. Knowledge of changes in seabird populations is also inherently important because seabirds play important roles in island and marine ecosystem processes, function and resilience, by acting as predators, scavengers, cross-ecosystem nutrient subsidizers, and ecosystem engineers [2, 13–16].

Despite the global importance of seabirds, both to marine ecosystems and as indicators of marine ecosystem status, analysis of their population trends is typically limited to the relatively small spatial and temporal scales at which data are collected. The only global assessment of seabird population status, based on extinction risk as assessed by the IUCN Red List of Threatened Species, indicates that one third of seabird species are threatened with extinction, one half are known or suspected to be in decline, and at least four species are extinct [12].

To investigate overall patterns in the world’s seabird population data over an ecologically-relevant timeframe, we assembled a global database of seabird population size records and applied multivariate autoregressive state-space (MARSS) modeling to estimate the global trajectory of all seabird populations with sufficient data (i.e., at least five records of population size between 1950 and 2010).

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Source et suite de l'article: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0129342

Sur le même blog: http://pocombelles.over-blog.com/article-les-oiseaux-meurent-au-perou-105025096.html