Aquaculture induced erosion of tropical coastlines throws coastal communities back into poverty

Shallow tropical coastlines harbour unique mangrove ecosystems, which support livelihoods and provide a natural barrier against coastal flooding. Non-sustainable land-use practices, such as large-scale clear cutting of mangroves for aquaculture, ground water withdrawal and alteration of river flows, result in rapid subsidence. The collapse of aquaculture production, due to pollution and disease, is followed by coastal erosion, damage to infrastructure, intrusion of salt water and coastal flooding. Standard engineered interventions for protection often fail or are extremely expensive in these soft muddy environments. Subsidence and erosion render re-planting of mangroves in front of retreating coastlines impossible. Short-term solutions should focus on restoration of abiotic conditions, such as hydrology and sediment fluxes, to facilitate rapid establishment of protective mangrove belts. However, to ensure long-term sustainability, improved governance frameworks are required that put in place criteria for sustainable aquaculture, guide coastal infrastructure designs and limit ground water extraction

Ontwikkeling van eilandstaarten : geomorfologie, waterhuishouding en vegetatie

In deze rapportage worden de oostelijke, buitendijkse delen van de Nederlandse Waddeneilanden behandeld, de zgn. eilandstaarten. Wanneer deze volledig ontwikkeld zijn bestaat ze uit wadplaten, kwelders en duinen. Dit rapport behandelt de geomorfologie, waterhuishouding en vegetatie van eilandstaarten. De ontwikkeling van eilandstaarten is mede van belang voor de functie die ze hebben in de waterveiligheid

Distinct habitat types arise along a continuous hydrodynamic stress gradient due to interplay of competition and facilitation

Though species interactions across local environmental gradients are well studied, the way in which species interactions shift between different habitats on a landscape scale has received less attention. We hypothesised that interactions among a suite of shoreline plant species shift across a hydrodynamic-exposure gradient, leading to generation of apparently distinct habitat types (e.g. bare cobble beaches, vegetated cobble beaches, fringing marshes and salt marshes). We examined hydrodynamic forcing and found that it was strongly correlated with shoreline habitat type. A transplant experiment revealed that all plants were rapidly crushed and abraded in bare cobble areas with high hydrodynamic energy and were out-competed by grasses in the low-energy salt marshes. Vegetated cobble beaches are inhabited by the largest amount of plant species under intermediate conditions, where hydrodynamic energy is sufficiently low to allow the establishment of the ecosystem engineer Spartina and sufficiently high to prevent the monopolisation of space by competitively dominant, but stress intolerant grasses. Experimentally reducing physical and biotic stresses (hydrodynamics and interspecific competition) on bare cobble beaches and salt marshes, respectively, enabled forbs to persist across the whole gradient. These results demonstrate that the outcome of interspecific interactions at landscape scales is driven by background physical conditions, and that this can result in the development of what are considered distinct habitats.

Stuurbaarheid van kwelders

Het beheer van de kwelderwerken in de Nederlandse Waddenzee is dusdanig, dat snel ingegrepen kan worden als er ongewenste achteruitgang zou ontstaan. Echter, kwelders kunnen door hun karakteristieke dynamiek en terugkoppelings-mechanismen onverwacht (niet-lineair) reageren als bepaalde grenzen van sturende factoren worden overschreden. Daarom is het belangrijk om de ontwikkeling van kwelders te blijven monitoren en het systeembegrip op orde te hebben, zodat er ingegrepen kan worden wanneer het nodig is. De stuurbaarheid is afhankelijk van de mate waarin de mens wil ingrijpe

Strong effects of a plantation with Pinus patula on Andean Subparamo vegetation: a case study from Columbia

The effect of a pine plantation on a native subparamo system in the Andes of Colombia (3 100 In above sea level) was studied. The vegetation of an 8 year-old plantation with Pinus patula was compared to that of the surrounding native subparamo. 59 plots made in the subparamo vegetation contained 121 vascular plant species. These plots were classified into three subparamo communities and one Andean scrub community. Sixty-four plots made in the pine plantation contained 76 vascular plant species and were subdivided into four classes of pine cover. With increasing pine cover, pine plantation plots tended to become less similar to the subparamo communities. Habitat-specific subp ramo species tended to disappear with increasing pine cover. After controlling for the effects of environmental variables in a partial canonical correspondence analysis, pine cover had a significant impact on plant species patterns. It is concluded that afforestation with Pinus patula resulted in strong negative effects on diversity and composition of the subparamo vegetation at the study site. (C) 2003 Elsevier Ltd. All rights reserved

Pole and pontoon hulas: An effective way of ecological engineering to increase productivity and biodiversity in the hard-substrate environment of the port of rotterdam

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