Coastal waters are increasingly degraded worldwide through human activities on land. Because coastal waters have open boundaries to the ocean, there are no simple local engineering solutions to maintain or restore their ecosystem health and the ecological services that they provide. In coastal waters, further applications of ecohy-drology are the use of macrophytes to enhance the internal consumption rate, and benthic suspension feeders, such as bivalve mollusks, sponges, tunicates, and polychaetes, to filter and pelletize excess nutrients and plankton. As detailed in Estuary Restoration, attempts to restore coastal water quality by planning to restore seagrass beds and coral reefs are bound to fail until the land-use practices that degraded these habitats in the first place are modified.
The only ecologically sustainable management strategy for coastal waters is adopting ecohydrology as the guiding principle for managing human activities on land while at the same time protecting fisheries, implementing a fisheries buy-out program, and using engineering and technology to treat sewage and storm water. Ecohydrology science offers a number of solutions, including top-down and bottom-up ecological manipulation and the creation and restoration of wetlands to help restore the health of rivers and estuarine waters. This ecological engineering approach can be combined with some technological fixes, such as the creation of freshets and smarter land use. This necessitates changing present governmental practices based on political geography or specific activities (e.g., farming, water resources, fisheries, and urban developments). Generally, the political geography limits or the usage units do not coincide with the basin boundaries. The ecohydrology approach also necessitates a high level of collaboration among stakeholders in order to develop best practices. Without these changes, estuaries and coastal waters will continue to degrade worldwide, despite local integrated coastal management plans that are implemented.
This solution is easy to preach and a nightmare to implement, mainly for political and socioeconomic reasons. Worldwide, the implementation of this science-based strategy will most likely stall until a political solution is found to regulate human activities on land. Indeed, local farmers, fishermen, and urban developers are often at odds with the imposition of land use, water resources, and fishery management rules that they claim jeopardize their ability to earn a living.
The coastal water ecosystem modeler is faced with complex processes and feedback processes between physics and biology, which often cannot be fully quantified because the data are inadequate. Models should not be seen as able to replace reality and the need for field observations.
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