Department of Biological Sciences, Humboldt State University, 1 Harpst Street, Arcata, California 95521, USA.
Ecol Appl. 2012 Sep;22(6):1743-61. doi: 10.1890/11-1083.1.
Managers need to predict how animals will respond to habitat redistributions caused by climate change. Our objective was to model the effects of sea level rise on total eelgrass (Zostera marina) habitat area and on the amount of that area that is accessible to Brant geese (Branta bernicla), specialist grazers of eelgrass. Digital elevation models were developed for seven estuaries from Alaska, Washington, California (USA), and Mexico. Scenarios of future total eelgrass area were derived from combinations of estuarine specific sediment and tectonic rates (i.e., bottom change rate) with three rates of eustatic sea level rise (ESLR). Percentages of total eelgrass areas that were accessible to foraging Brant were determined for December when the birds overwinter at more southerly sites and in April as they move north to sites where they build body stores on their way to nesting areas in Alaska. The modeling showed that accessible eelgrass area could be lower than total area due to how daytime low-tide height, eelgrass shoot length, and the upper elevation of eelgrass determined Brant-reaching depth. Projections of future eelgrass area indicated that present-day ESLR (2.8 mm/yr) and bottom change rates should sustain the current pattern of estuarine use by Brant except in Morro Bay, where use should decrease because eelgrass is being ejected from this estuary by a positive bottom change rate. Higher ESLR rates (6.3 and 12.7 mm/yr) should result in less Brant use of estuaries at the northern and southern ends of the flyway, particularly during the winter, but more use of mid-latitude estuaries. The capacity of mid-latitude estuaries to function as Brant feeding refugia, or for these estuaries and Izembek Lagoon to provide drift rather than attached leaves, is eventually limited by the decrease in total eelgrass area, which is a result of a light extinction affect on the eelgrass, or the habitat being pushed out of the estuary by positive tectonic rates. Management responses are limited to the increase or decrease of sediment supply and the relocation of levees to allow for upslope migration of eelgrass habitat.
经理们需要预测动物将如何应对气候变化导致的栖息地重新分配。我们的目标是建立一个模型，以评估海平面上升对总鳗草（Zostera marina）栖息地面积的影响，以及鳗草对伯氏滨鹬（Branta bernicla）的可及性，伯氏滨鹬是鳗草的专门食草动物。为美国阿拉斯加、华盛顿和加利福尼亚的七个河口以及墨西哥的河口开发了数字高程模型。未来总鳗草面积的情景是根据河口特定的沉积物和构造速率（即底部变化速率）与三种海平面上升速率（即海平面上升率）的组合得出的。确定了 12 月候鸟在较南部越冬时和 4 月向北迁徙到在前往阿拉斯加筑巢区的途中储存身体脂肪的地点时，可觅食伯氏滨鹬的总鳗草面积的百分比。该模型表明，由于白天低潮高度、鳗草芽长度以及鳗草的上限如何决定伯氏滨鹬的可达深度，可及鳗草面积可能低于总面积。对未来鳗草面积的预测表明，目前的海平面上升率（2.8 毫米/年）和底部变化率应维持伯氏滨鹬目前对河口的使用模式，除非在莫罗湾，由于底部变化率为正值，鳗草正被从这个河口排出，否则这里的使用应该会减少。更高的海平面上升率（6.3 和 12.7 毫米/年）可能会导致候鸟在飞行路线的北端和南端对河口的使用减少，特别是在冬季，但对中纬度河口的使用会增加。中纬度河口作为伯氏滨鹬觅食避难所的能力，或者这些河口和伊泽姆贝格泻湖提供漂移而不是附着的叶子的能力，最终会受到鳗草总面积减少的限制，这是由于对鳗草的光衰减效应，或由于构造速率为正值，栖息地被推出河口。管理对策仅限于增加或减少沉积物供应以及重新安置堤坝，以允许鳗草栖息地向上坡迁移。
