Thousands of artificial (‘human-made ’ ) structures are present in the marine environment, many at or approaching end-of-life and requiring urgent decisions regarding their decommissioning. No consensus has been reached on which decommissioning option(s) result in optimal environmental and societal outcomes, in part, owing to a paucity of evidence from real-world decommissioning case studies. To address this significant chal- lenge, we asked a worldwide panel of scientists to provide their expert opinion. They were asked to identify and characterise the ecosystem effects of artificial structures in the sea, their causes and consequences, and to identify which, if any, should be retained following decommissioning. Experts considered that most of the pressures driving ecological and societal effects from marine artificial structures (MAS) were of medium severity, occur frequently, and are dependent on spatial scale with local-scale effects of greater magnitude than regional effects. The duration of many effects following decommissioning were considered to be relatively short, in the order of days. Overall, environmental effects of structures were considered marginally undesirable, while societal effects marginally desirable. Experts therefore indicated that any decision to leave MAS in place at end-of-life to be more beneficial to society than the natural environment. However, some individual environmental effects were considered desirable and worthy of retention, especially in certain geographic locations, where structures can support improved trophic linkages, increases in tourism, habitat provision, and population size, and provide stability in population dynamics. The expert analysis consensus that the effects of MAS are both negative and positive for the environment and society, gives no strong support for policy change whether removal or retention is favoured until further empirical evidence is available to justify change to the status quo. The combination of desirable and undesirable effects associated with MAS present a significant challenge for policy- and decision- makers in their justification to implement decommissioning options. Decisions may need to be decided on a case-by-case basis accounting for the trade-off in costs and benefits at a local level.
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The Wasatchian Wa-0 mammalian fauna from the Paleocene-Eocene Thermal Maximum (earliest Eocene) is reasonably well sampled in North America, but mammals of small body size are still poorly known. Here we describe a new species of the insectivore Didelphodus based on a cranial rostrum, both dentaries, and a nearly complete upper and lower dentition, all found by screen-washing. The new species, D. caloris, is the oldest species of the genus known in North America. It differs from later early Eocene Didelphodus in being substantially smaller, in having relatively simple premolars, and in having a more reduced M3 relative to preceding molars. Precursors of Didelphodus are not known with certainty, and the species D. caloris may be an immigrant to mid-continent North America. D. caloris is tentatively interpreted as a dwarfed form like other Wa-0 mammals because of its small size relative to the better-known successor species D. absarokae.
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