Entity

Time filter

Source Type

Montevideo, Uruguay

Defeo O.,UNDECIMAR | McLachlan A.,Nelson Mandela Metropolitan University
Geomorphology | Year: 2013

Global patterns in species richness in sandy beach ecosystems have been poorly understood until comparatively recently, because of the difficulty of compiling high-resolution databases at continental scales. We analyze information from more than 200 sandy beaches around the world, which harbor hundreds of macrofauna species, and explore latitudinal trends in species richness, abundance and biomass. Species richness increases from temperate to tropical sites. Abundance follows contrasting trends depending on the slope of the beach: in gentle slope beaches, it is higher at temperate sites, whereas in steep-slope beaches it is higher at the tropics. Biomass follows identical negative trends for both climatic regions at the whole range of beach slopes, suggesting decreasing rates in carrying capacity of the environment towards reflective beaches. Various morphodynamic variables determine global trends in beach macrofauna. Species richness, abundance and biomass are higher at dissipative than at reflective beaches, whereas a body size follows the reverse pattern. A generalized linear model showed that large tidal range (which determines the vertical dimension of the intertidal habitat), small size of sand particles and flat beach slope (a product of the interaction among wave energy, tidal range and grain size) are correlated with high species richness, suggesting that these parameters represent the most parsimonious variables for modelling patterns in sandy beach macrofauna. Large-scale patterns indicate a scaling of abundance to a body size, suggesting that dissipative beaches harbor communities with highest abundance and species with the smallest body sizes. Additional information for tropical and northern hemisphere sandy beaches (underrepresented in our compilation) is required to decipher more conclusive trends, particularly in abundance, biomass and body size. Further research should integrate meaningful oceanographic variables, such as temperature and primary production, in deciphering latitudinal trends. © 2013 Elsevier B.V. Source


McLachlan A.,University of Sydney | Defeo O.,UNDECIMAR | Jaramillo E.,Austral University of Chile | Short A.D.,University of Sydney
Ocean and Coastal Management | Year: 2013

This paper addresses the need for a simple model for managers to employ when planning strategies for management of sandy beaches. It is based on the premise that in the overwhelming majority of cases beaches are suitable for recreation or for conservation or a combination of the two, whereas other uses are rare. The broad range of physical, ecological and socio-economic factors relevant to beaches, are reviewed briefly. Then three key factors are selected to develop each of two simple indices, an index of conservation value, CI, based on dune state of health, the presence of iconic species and macrobenthic species richness; and an index of recreation potential, RI, based on the extent of infrastructure, the level of safety/health of the beach and its physical carrying capacity. By combining these two indices, a beach can be simply classified as suitable for intensive recreation, or primarily for conservation, or for mixed use. Ten principles are outlined for consideration and potential application to beach management strategies. Finally, 23 beaches from three continents are classified, with detailed descriptions of a beach typical of each major use type. © 2012 Elsevier Ltd. Source


Defeo O.,UNDECIMAR | Castilla J.C.,University of Santiago de Chile
Current Opinion in Environmental Sustainability | Year: 2012

We discuss coastal shellfisheries management and governance models in Latin America and the Caribbean (LAC) at different scales. Self-imposed governance with spatial property rights, internal rules and co-management resulted in successful local shellfisheries. At the national level, the long-term Chilean governability system, which included sea-zoning for artisanal and industrial fleets and exclusive allocation of rights to artisanal shellfish communities, successfully tamed wicked management problems. However, the combination of weak governance, globalization of markets, fishing pressure and climate change exacerbated depletion patterns in most LAC shellfisheries. Increasing market prices exceed the low costs of harvesting low abundance coastal shellfish, and together with illegal trade, have driven some species to levels close to extinction (anthropogenic Allee effect). Mass shellfish mortalities driven by climate variability are threatening stocks and may swamp management and governance schemes. Coastal shellfisheries urgently require the implementation of resilient management and effective long-term governance schemes under pressing conditions of change and uncertainty. © 2012 Elsevier B.V. Source


Gutierrez N.L.,University of Washington | Hilborn R.,University of Washington | Defeo O.,UNDECIMAR
Nature | Year: 2011

One billion people depend on seafood as their primary source of protein and 25% of the world's total animal protein comes from fisheries. Yet a third of fish stocks worldwide are overexploited or depleted. Using individual case studies, many have argued that community-based co-management should prevent the tragedy of the commons because cooperative management by fishers, managers and scientists often results in sustainable fisheries. However, general and multidisciplinary evaluations of co-management regimes and the conditions for social, economic and ecological success within such regimes are lacking. Here we examine 130 co-managed fisheries in a wide range of countries with different degrees of development, ecosystems, fishing sectors and type of resources. We identified strong leadership as the most important attribute contributing to success, followed by individual or community quotas, social cohesion and protected areas. Less important conditions included enforcement mechanisms, long-term management policies and life history of the resources. Fisheries were most successful when at least eight co-management attributes were present, showing a strong positive relationship between the number of these attributes and success, owing to redundancy in management regulations. Our results demonstrate the critical importance of prominent community leaders and robust social capital, combined with clear incentives through catch shares and conservation benefits derived from protected areas, for successfully managing aquatic resources and securing the livelihoods of communities depending on them. Our study offers hope that co-management, the only realistic solution for the majority of the world's fisheries, can solve many of the problems facing global fisheries. ©2011 Macmillan Publishers Limited. All rights reserved. Source


Defeo O.,UNDECIMAR | McLachlan A.,University of Sydney
Marine Ecology Progress Series | Year: 2011

Species richness and abundance of macrofauna on sandy shores increase from micro - tidal reflective to macrotidal dissipative beach conditions. However, no attempt has been made to deconstruct these patterns. Using information on the macrofauna from 63 microtidal sandy beach surveys in South America, we deconstructed the community to discriminate among taxonomic groups, supralittoral and intertidal forms, and groups with different feeding habits and development modes. We also separated the effects of development mode and beach zone (intertidal vs. supralittoral) at the species level and scaled body size to density estimates. Total species richness decreased towards reflective beaches, but this trend was less marked in crustaceans than in molluscs or polychaetes. Supralittoral air-breathing crustaceans increased in richness and abundance from dissipative to reflective conditions, a reverse trend to that seen in intertidal crustaceans. Development modes (species with direct development and with planktonic larvae) showed the same response to beach type as the community as a whole. Filter feeders, scavengers and deposit feeders showed the same trend, but the latter were scarce or absent on reflective beaches. Zone was more important than either development or feeding modes in determining individual species responses to beach type. Body size decreased and density increased from reflective to dissipative beaches, suggesting that smaller forms are more sensitive to harsh conditions where density is lower, and hence there is less scope for biological interactions in reflective beaches. The deconstruction approach provided insights into the relationships between life cycle characteristics and richness and abundance patterns and the relative importance of environmental variables in beach ecology. © Inter-Research 2011 www.int-res.com. Source

Discover hidden collaborations