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Auteur Llope, M.; Daskalov, G.M.; Rouyer, T.; Mihneva, V.; Chan, K.-S.; Grishin, A.N.; Stenseth, N.C.
Titre Overfishing of top predators eroded the resilience of the Black Sea system regardless of the climate and anthropogenic conditions Type Article scientifique
Année 2010 Publication Revue Abrégée Global Change Biology
Volume 17 Numéro 3 Pages 1251-1265
Mots-Clés Black Sea; ecological thresholds; ecosystem resilience; eutrophication; Gam; Regime shifts; Scenarios; trophic regulation
Résumé It is well known that human activities, such as harvesting, have had major direct effects on marine ecosystems. However, it is far less acknowledged that human activities in the surroundings might have important effects on marine systems. There is growing evidence suggesting that major reorganization (i.e., a regime shift) is a common feature in the temporal evolution of a marine system. Here we show, and quantify, the interaction of human activities (nutrient upload) with a favourable climate (run-off) and its contribution to the eutrophication of the Black Sea in the 1980s. Based on virtual analysis of the bottom-up (eutrophication) vs. top-down (trophic cascades) effects, we found that an earlier onset of eutrophication could have counteracted the restructuring of the trophic regulation at the base of the food web that resulted from the depletion of top predators in the 1970s. These enhanced bottom-up effects would, however, not propagate upwards in the food web beyond the zooplankton level. Our simulations identified the removal of apex predators as a key element in terms of loss of resilience that inevitably leads to a reorganization. Once the food web has been truncated, the type and magnitude of interventions on the group replacing the apex predator as the new upper trophic level have no effect in preventing the trophic cascade. By characterizing the tipping point at which increased bottom-up forcing exactly counteracts the top-down cascading effects, our results emphasize the importance of a comprehensive analysis that take into account all structuring forces at play (including those beyond the marine system) at a given time.
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ISSN 1365-2486 ISBN Médium
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Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1671
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Auteur Meynard, C.N.; Kaplan, D.M.; Leroy, B.
Titre Detecting outliers in species distribution data: Some caveats and clarifications on a virtual species study Type Article scientifique
Année 2019 Publication Revue Abrégée J. Biogeogr.
Volume 46 Numéro 9 Pages 2141-2144
Mots-Clés enm; observation errors; outliers; prevalence; probabilistic approach; sample bias; simulations; species distribution models; thresholds; virtual ecology; virtual species
Résumé Liu et al. (2018) used a virtual species approach to test the effects of outliers on species distribution models. In their simulations, they applied a threshold value over the simulated suitabilities to generate the species distributions, suggesting that using a probabilistic simulation approach would have been more complex and yield the same results. Here, we argue that using a probabilistic approach is not necessarily more complex and may significantly change results. Although the threshold approach may be justified under limited circumstances, the probabilistic approach has multiple advantages. First, it is in line with ecological theory, which largely assumes non-threshold responses. Second, it is more general, as it includes the threshold as a limiting case. Third, it allows a better separation of the relevant intervening factors that influence model performance. Therefore, we argue that the probabilistic simulation approach should be used as a general standard in virtual species studies.
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Langue English Langue du Résumé Titre Original
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Volume de collection Numéro de collection Edition
ISSN 0305-0270 ISBN Médium
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Notes WOS:000483602900019 Approuvé pas de
Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2640
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Auteur Shin, Y.-J.; Bundy, A.; Shannon, L.J.; Simier, M.; Coll, M.; Fulton, E.A.; Link, J.S.; Jouffre, D.; Ojaveer, H.; Mackinson, S.; Heymans, J.J.; Raid, T.
Titre Can simple be useful and reliable? Using ecological indicators to represent and compare the states of marine ecosystems Type Article scientifique
Année 2010 Publication Revue Abrégée Ices Journal of Marine Science
Volume 67 Numéro 4 Pages 717-731
Mots-Clés comparative approach; indicators; marine ecosystems; reference levels; thresholds
Résumé Within the IndiSeas WG, the evaluation of exploited marine ecosystems has several steps, from simple binary categorization of ecosystems to a more-complex attempt to rank them and to evaluate their status using decision-tree analyses. With the intention of communicating scientific knowledge to the public and stakeholders, focus is on evaluating and comparing the status of exploited marine ecosystems using a set of six ecological indicators and a simple and transparent graphic representation of ecosystem state (pie charts). A question that arose was whether it was acceptable to compare different types of marine ecosystems using a generic set of indicators. To this end, an attempt is made to provide reference levels to which ecosystems can be objectively compared. Unacceptable thresholds for each indicator are determined based on ecological expertise derived from a questionnaire distributed to a group of scientific experts. Analysis of the questionnaires revealed no significant difference in the thresholds provided for different ecosystem types, suggesting that it was reasonable to compare states directly across different types of ecosystem using the set of indicators selected.
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ISSN 1054-3139 ISBN Médium
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Numéro d'Appel LL @ pixluser @ collection 105
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