Ecoengineering with Ecohydrology: Successes and failures in estuarine restoration

© 2016 Elsevier Ltd. Ecological Engineering (or Ecoengineering) is increasingly used in estuaries to re-create and restore ecosystems degraded by human activities, including reduced water flow or land poldered for agricultural use. Here we focus on ecosystem recolonization by the biota and their functioning and we separate Type A Ecoengineering where the physico-chemical structure is modified on the basis that ecological structure and functioning will then follow, and Type B Ecoengineering where the biota are engineered directly such as through restocking or replanting. Modifying the physical system to create and restore natural processes and habitats relies on successfully applying Ecohydrology, where suitable physical conditions, especially hydrography and sedimentology, are created to recover estuarine ecology by natural or human-mediated colonisation of primary producers and consumers, or habitat creation. This successional process then allows wading birds and fish to reoccupy the rehabilitated areas, thus restoring the natural food web and recreating nursery areas for aquatic biota. We describe Ecohydrology principles applied during Ecoengineering restoration projects in Europe, Australia, Asia, South Africa and North America. These show some successful and sustainable approaches but also others that were less than successful and not sustainable despite the best of intentions (and which may even have harmed the ecology). Some schemes may be 'good for the ecologists', as conservationists consider it successful that at least some habitat was created, albeit in the short-term, but arguably did little for the overall ecology of the area in space or time. We indicate the trade-offs between the short- and long-term value of restored and created ecosystems, the success at developing natural structure and functioning in disturbed estuaries, the role of this in estuarine and wetland management, and the costs and benefits of Ecoengineering to the socio-ecological system. These global case studies provide important lessons for both the science and management of estuaries, including that successful estuarine restoration is a complex and often difficult process, and that Ecoengineering with Ecohydrology aims to control and/or simulate natural ecosystem processes

Salmon at River\u27s End: The Role of the Estuary in the Decline and Recovery of Columbia River salmon

The continued decline of Columbia River salmon (Oncorhynchus spp.) populations has long focused concerns on habitat changes upriver, particularly the effects of large hydroelectric dams. Increasing evidence that ocean conditions strongly influence salmon production, however, has raised questions about the importance of the estuarine environment to salmon and whether the hydropower system has affected estuarine-rearing habitats. In response to Northwest Power Planning Council recommendations, we initiated a review of what is known about the effects of the hydroelectric system on the hydrology, habitats, and ecology of the Columbia River estuary. Our goal was to develop recommendations for improving estuarine conditions or to identify research that may be needed before appropriate salmon-management changes can be defined. Our review and analyses addressed four major questions: (1) What habitats and processes support native salmon populations during the estuarine phase of their life cycle? (2) Have changes to the estuary had a significant role in salmon decline? (3) What have been the impacts of flow regulation on the hydrology, habitat, and biological interactions in the estuarine ecosystem? (4) What estuarine conditions are necessary to maintain salmonid diversity in the Columbia River basin

Variation in juvenile Chinook salmon diet composition and foraging success between two estuaries with contrasting land-use histories

The transition of juveniles from fresh water to estuarine and marine environments is a critical period in the life cycle of Pacific salmon, during which survival can be strongly size-selective. Because the amount and quality of food consumed are major determinants of juvenile salmon growth, successful acquisition of energy rich prey during estuarine residence is critical for survival. Humans have likely impacted the feeding relationships of juvenile salmon in estuaries by destroying estuarine wetlands and by altering the abundance of salmon in estuaries. While the estuarine foraging habits of juvenile salmon have been extensively examined, few studies have conducted quantitative comparisons between estuaries that have experienced different levels of human modification. However, comparisons between whole estuaries with different degrees of wetland loss and degradation may be a useful scale of analysis for the diet composition and consumption rates of mobile consumers such as juvenile salmon. To improve our understanding of the effects of wetland loss and conspecific density on juvenile Chinook salmon consumption rate and diet composition in estuaries, we assembled Chinook salmon density and diet data from two Salish Sea estuaries with dramatically different levels of wetland loss and modification. We compared juvenile Chinook salmon diet composition, diet energy density, and instantaneous ration (a proxy for consumption rate) between the two estuaries. We also evaluated the effect of conspecific density on instantaneous ration. We found significant differences in diet composition between juvenile Chinook salmon in the two estuaries, but little difference in instantaneous ration or diet energy density. However, in the highly modified estuary, conspecific density had a significant, negative effect on instantaneous ration, while in the more natural estuary there was little effect on instantaneous ration. These findings suggest that wetland loss may interact with salmon density to constrain the consumption rates of juvenile salmon in estuaries, with resulting consequences for growth and survival

Geographic Variation in Salt Marsh Structure and Function for Nekton: a Guide to Finding Commonality Across Multiple Scales

Coastal salt marshes are distributed widely across the globe and are considered essential habitat for many fish and crustacean species. Yet, the literature on fishery support by salt marshes has largely been based on a few geographically distinct model systems, and as a result, inadequately captures the hierarchical nature of salt marsh pattern, process, and variation across space and time. A better understanding of geographic variation and drivers of commonalities and differences across salt marsh systems is essential to informing future management practices. Here, we address the key drivers of geographic variation in salt marshes: hydroperiod, seascape configuration, geomorphology, climatic region, sediment supply and riverine input, salinity, vegetation composition, and human activities. Future efforts to manage, conserve, and restore these habitats will require consideration of how environmental drivers within marshes affect the overall structure and subsequent function for fisheries species. We propose a future research agenda that provides both the consistent collection and reporting of sources of variation in small-scale studies and collaborative networks running parallel studies across large scales and geographically distinct locations to provide analogous information for data poor locations. These comparisons are needed to identify and prioritize restoration or conservation efforts, identify sources of variation among regions, and best manage fisheries and food resources across the globe

UN Decade on Ecosystem Restoration 2021–2030: what chance for success in restoring coastal ecosystems?

On 1 March 2019, the United Nations (UN) General Assembly (New York) declared 2021–2030 the “UN Decade on Ecosystem Restoration.” This call to action has the purpose of recognizing the need to massively accelerate global restoration of degraded ecosystems, to fight the climate heating crisis, enhance food security, provide clean water and protect biodiversity on the planet. The scale of restoration will be key; for example, the Bonn Challenge has the goal to restore 350 million km2 (almost the size of India) of degraded terrestrial ecosystems by 2030. However, international support for restoration of “blue” coastal ecosystems, which provide an impressive array of benefits to people, has lagged. Only the Global Mangrove Alliance (https://mangrovealliance.org/) comes close to the Bonn Challenge, with the aim of increasing the global area of mangroves by 20% by 2030. However, mangrove scientists have reservations about this target, voicing concerns that it is unrealistic and may prompt inappropriate practices in attempting to reach this target (Lee et al., 2019). The decade of ecosystem restoration declaration also coincides with the UN Decade of Ocean Science for Sustainable Development, which aims to reverse deterioration in ocean health. If executed in a holistic and coordinated manner, signatory nations could stand to deliver on both these UN calls to action

Juveline Salmon Utilization of Freshwater Tidal Ecosystems: an Essential Restoration Link?

Simenstad will provide an overview of tidal freshwater ecosystems. These systems are complex and highly variable ecotones between fluvial and estuarine processes. They are particularly important in dynamic migration and rearing of juvenile Pacific salmon. Watershed and floodplain changes have modified that function, particularly relative to salmon life history diversity. Are habitat opportunity and capacity in the lower estuary extensively supplemented by tidal freshwater? Restoration strategies tend to discount potential role of freshwater tidal ecosystems, especially scrub-shrub and forested tidal wetlands and floodplains, in salmon recovery

ADF&G-OCS Fish food habits analysis

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