Browsing by Subject "POPULATION-DENSITY"

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Open Access
A baseline paleoecological study for the Santa Cruz Formation (late–early Miocene) at the Atlantic coast of Patagonia, Argentina
(Palaeogeography, Palaeoclimatology, Palaeoecology, 2010-06) Vizcaíno, SF; Bargo, MS; Kay, RF; Fariña, RA; Di Giacomo, M; Perry, JMG; Prevosti, FJ; Toledo, N; Cassini, GH; Fernicola, JC
Coastal exposures of the Santa Cruz Formation (late-early Miocene, southern Patagonia, Argentina) between the Coyle and Gallegos rivers have been a fertile ground for recovery of Miocene vertebrates for more than 100 years. The formation contains an exceptionally rich mammal fauna, which documents a vertebrate assemblage very different from any living community, even at the ordinal level. Intensive fieldwork performed since 2003 (nearly 1200 specimens have been collected, including marsupials, xenarthrans, notoungulates, litopterns astrapotheres, rodents, and primates) document this assertion. The goal of this study is to attempt to reconstruct the trophic structure of the Santacrucian mammalian community with precise stratigraphic control. Particularly, we evaluate the depauperate carnivoran paleoguild and identify new working hypotheses about this community. A database has been built from about 390 specimens from two localities: Campo Barranca (CB) and Puesto Estancia La Costa (PLC). All species have been classified as herbivore or carnivore, their body masses estimated, and the following parameters estimated: population density, on-crop biomass, metabolic rates, and the primary and secondary productivity. According to our results, this model predicts an imbalance in both CB and PLC faunas which can be seen by comparing the secondary productivity of the ecosystem and the energetic requirements of the carnivores in it. While in CB, the difference between carnivores and herbivores is six-fold, in PLC this difference is smaller, the secondary productivity is still around three times that of the carnivore to herbivore ratio seen today. If both localities are combined, the difference rises to around four-fold in favour of secondary productivity. Finally, several working hypotheses about the Santacrucian mammalian community and the main lineages of herbivores and carnivores are offered. © 2010 Elsevier B.V. All rights reserved.
Open Access
Local Institutional Responses to Global Market Pressures: The Sea Cucumber Trade in Yucatán, Mexico
(World Development, 2018-02-01) Bennett, A; Basurto, X
© 2017 Elsevier Ltd The expansion of global seafood trade creates opportunities as well as risks for small-scale fisheries (SSFs) livelihoods. Markets provide economic opportunity, but without effective governance, high demand can drive resource degradation. In the context of small-scale sea cucumber fisheries in Yucatán, Mexico, this study documents local governance responses to new markets and identifies factors driving those responses. We conducted a comparative case study of two SSF communities, collecting participant observation and interview data during 16 months of fieldwork. Our study found that local rules-in-use did not match government regulations and that the emergence of local rules was shaped by relations of production in each study site. Specifically, patron–client relationships promoted an open access regime that expanded local fishing fleets while fishing cooperatives attempted to restrict access to local fishing grounds through collective action and multi-level linkages with government. We propose that the different material incentives arising from the way that patron–client relationships and cooperatives organize labor, capital, and profits help explain these divergent governance responses. We hypothesize that this finding is generalizable beyond the study context, especially given that patron–client relationships and cooperatives are common throughout the world's SSFs. This finding builds on previous research that indicates local institutions can mediate the effects of market pressures, showing that the emergence of local rules depends on how resource users are organized not just in relation to resource governance but vis-à-vis the markets themselves. Therefore, effective policies for SSFs facing market pressures require a greater emphasis on regulating local-level trade and governing the commercial aspects of fishing livelihoods. These lessons are relevant to the estimated 540 million individuals whose livelihoods SSFs support who may increasingly engage in the global seafood trade.