Ecological restoration of tidal estuaries in North Western Europe: an adaptive strategy to multi-scale changes

Abstract

Abstract:Estuaries are subject to increasing pressures due to local human activities. In addition, global change is affecting coastal habitats. Such disturbances impinge on goods and services provided by these ecosystems. The paper is devoted to efforts to restore environmental quality in some industrialised estuaries during the few past decades. It then compares strategies to recover damaged habitats and methods to restore lost ecological functionalities. Case studies are taken from the Seine in France, the Humber in England, the Scheldt in Belgium and the Netherlands and the Elbe in Germany. The article retraces briefly the morphological and ecological changes which have been inflicted on the estuaries over the last century. It puts into light actions which have been successful in improving their ecological functioning. Through comparing the various restoration schemes, policies are assessed. Details are given on efforts made lately in the Seine estuary which has lost more than 90% of its intertidal areas in about 150 years. Recently, losses due to an extension of harbour facilities in le Havre ("Port 2000") have been compensated by the rehabilitation of a former mud flat and various constructions such as an artificial island for birds.The discussion confronts the present management of tidal estuaries to future challenges, including global changes. Such changes will not only include global warming and its consequences (sea level rise, biogeochemical cycles alteration . . .), but also socio-economic adjustments and a possible geo-political reorganization expected to take place in relation to increased harbour activities and the increasing need for more space dedicated to natural habitats and leisure activities (sports, tourism . . .).The conclusion puts together the various approaches from the considered European estuaries. Resting on a rigorous scientific approach, it proposes a synthetic approach to restoration:1. Efficient procedures of socio-ecological evaluation, 2. A methodology to assess the ecological quality of systems considered, 3. Rigorous monitoring programs, resting on a relevant choice of indicators, and 4. Participation of local communities, in order to define strategies compatible with conservation and sustainable development at the local, regional and European levels.

Modeling the biogeochemical functioning of the Seine estuary and its coastal zone: Export, retention, and transformations

“…In 1998, an extension project for Le Havre harbor (Port 2000) was approved, and several compensatory actions were planned to keep the balance between the economic development objectives and the protection of aquatic habitats. In a first restoration effort in 2005 some breaches were opened in the dykes to favor the connectivity between the estuary and the nearby salt marshes (Ducrotoy and Dauvin ; Ducrotoy , and references therein).…”

Long term anthropogenic changes and ecosystem service consequences in the northern part of the complex Rhine-Meuse estuarine system

“…The implementation of the Kierbesluit is now foreseen for mid-2018 and is a separate decision that does not prelude a further recovery of the estuarine dynamics (Staf Deltacommissaris, 2013) This implies that it is not very likely that the near future will see a recovery of estuarine dynamics and hence of soft estuarine ecotopes within the Rhine-Meuse estuary. This policy is at odds with NWP and the recommendations of DC II, and contrasts with the development of estuarine restoration elsewhere in Europe (Attrill, 1998, Dauvin, 2006, Antheunisse and Verhoeven, 2006, Ducrotoy and Dauvin, 2008, Ducrotoy, 2010. The restoration of estuarine dynamics may however get a boost from a completely different side, that of safety.…”

Coastal use accelerated the regional sea-level rise

“…In Europe, many analytical and numerical models have been applied to estuary areas, e.g. the Ems, Schelde, Elbe and Seine estuaries, to estimate tidal range, storm surges and mixing and dispersion processes and evaluate the effects of coastal use (Frouin et al, 2007;Lebbe et al, 2008;Ducrotoy, 2010;Tessier et al, 2012). The Ems, for example, is a relatively well studied estuary and the relative research projects are focusing on tidal dynamics and affects of dredging in the high turbidity zone (Talke and Swart, 2006).…”