Abstract The floodplains of brackish coastal lagoons are subject to a highly dynamic hydrological regimen mainly due to their intermittent connection with the ocean. Coastal lagoons generally support fisheries, while livestock ranching and human settlements are found in the floodplain. Therefore, it is common practice to artificially open the sand barrier to avoid floods and manage fish stocks. Saltmarsh species are subject to grazing pressure and to changes in flooding and salinity regimens, affecting plants’ community structure. In the Laguna de Rocha Protected Landscape, a shallow brackish coastal lagoon located in Uruguay (South America), livestock ranchers complain about the spreading of the native cyperacea Juncus acutus L. The plant forms dense mats in the outermost zones of the floodplain, apparently displacing natural grasslands where the cattle graze. Also, stakeholders have encouraged the park authorities to artificially open the lagoon to obtain short-term benefits for fisheries and cattle raising. The study evaluated the increase in the surface area occupied by J. acutus and analyzed the possible causes of this increase as a basis for suggesting management actions. Historical and current aerial and satellite images, historical hydrological and climatic data and local ecological knowledge about the biology of the species and its spatial distribution over time were analyzed. The results indicate that J. acutus expanded in the floodplain of Laguna de Rocha, possibly starting ca. 2000, to cover less than 100 ha of the study area at low and high density. The results confirm most of the information obtained from the local stakeholders, whose local ecological knowledge was highly useful in understanding some local processes and providing information regarding periods for which data were not available. The expansion of J. acutus can be explained by a multiplicity of causes that acted synergistically to favor the species through a series of changes in the management of the sand barrier, livestock management and climate variability. However, a quantification of the economic effects of J. acutus on cattle feeding and fisheries is needed. Possible actions to control J. acutus expansion involve management of the grazing pressure using sheep, burning with fire, mechanical removal and avoiding artificial opening of the lagoon to allow larger and longer floods to occur and permit recovery of the previous, more natural hydrological regime. Our results suggest that it is important to be cautious before taking management actions to avoid costly solutions that are only short-term palliatives that could trigger other unforeseen environmental impacts.

中文翻译：

---

基于 GIS 的评估与当地生态知识相结合，以支持对在受保护沿海泻湖洪泛区蔓延的 Juncus acutus L. 进行管理

摘要 半咸水沿海泻湖泛滥平原受高动态水文方案的影响，主要是由于它们与海洋的间歇性连接。沿海泻湖通常支持渔业，而在洪泛区发现牲畜牧场和人类住区。因此，通常的做法是人为地打开沙障以避免洪水和管理鱼类种群。盐沼物种受到放牧压力以及洪水和盐度方案的变化，影响植物的群落结构。在位于乌拉圭（南美洲）的浅咸水沿海泻湖 Laguna de Rocha Protected Landscape 中，牲畜牧场主抱怨本地莎草属植物 Juncus acutus L 的蔓延。该植物在洪泛区的最外围区域形成密集的垫子，显然取代了牛吃草的天然草原。此外，利益相关者鼓励公园当局人为地开放泻湖，以获得渔业和养牛的短期利益。该研究评估了尖头刺猬所占表面积的增加，并分析了这种增加的可能原因，作为建议管理措施的基础。分析了历史和当前的航空和卫星图像、历史水文和气候数据以及有关物种生物学及其空间分布随时间变化的当地生态知识。结果表明 J. acutus 在 Laguna de Rocha 的洪泛区扩张，可能开始于大约 2000 年，以低密度和高密度覆盖不足 100 公顷的研究区域。结果证实了从当地利益相关者那里获得的大部分信息，他们的当地生态知识对于理解一些当地过程和提供有关数据不可得时期的信息非常有用。J. acutus 的扩张可以通过多种原因来解释，这些原因通过沙障管理、牲畜管理和气候变化的一系列变化协同作用有利于该物种。然而，需要量化 J. acutus 对牛饲养和渔业的经济影响。控制 J. acutus 扩张的可能行动包括使用绵羊管理放牧压力、用火焚烧、机械清除和避免人工开放泻湖以允许发生更大和更长的洪水并允许恢复以前的洪水，更自然的水文情势。我们的结果表明，在采取管理行动之前要谨慎，以避免代价高昂的解决方案，这些解决方案只是可能引发其他不可预见的环境影响的短期缓解措施。