Ecoengineering with Ecohydrology: Successes and failures in estuarine restoration

Abstract

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 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT2 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.

Effects of shoreline armouring and overwater structures on coastal and estuarine fish: opportunities for habitat improvement

“…Thus, there is great potential to align ecological, economic and human safety goals through shoreline rehabilitation projects (Elliott et al . ).…”

Maximizing the benefits of oyster reef restoration for finfish and their fisheries

“…Ecological restoration of oyster reefs for finfish and their fisheries is an important component of many coastal management and enhancement schemes (Baggett et al., ; Creighton, Boon, Brookes, & Sheaves, ; Humphries & La Peyre, ). Oyster reef restoration encompasses both categories of ecoengineering: Type A, the restoration of habitats thus allowing the desired species to colonize or expand; and Type B, which involves the direct increase in a species, such as through restocking or replanting (Elliott et al., ). Globally, 46 studies detail oyster restoration projects which seek to enhance finfish and/or their fisheries around reefs (as identified from the ISI Web of Knowledge; Figure , Table S1).…”

The state of the world’s mangroves in the 21st century under climate change

“…Huge efforts are being put into mangrove rehabilitation and creation at landscape scales. While such large-scale efforts are generally unsuccessful due to poor species selection, inappropriate choice of rehabilitation locations, and local governance issues (Lewis, 2005;Primavera & Esteban, 2008;Elliott et al, 2016;Kodikara et al, 2017), some efforts are becoming more successful as elements of species biology and hydrological requirements are incorporated into the design and implementation of rehabilitation projects (e.g., Matsui et al, 2010;Oh et al, 2017). On a larger scale, climate change may promote some positive gains, especially at the northern and southern latitudinal limits of mangroves, as mangroves encroach on and replace saltmarsh species in some localities, which was a major theme of the 4th Mangrove and Macrobenthos Meeting (MMM4) held in St. Augustine, Florida in 2016.…”