River Restoration & Biodiversity Conservation

cover_net 4/20/06 2:49 PM Pagina 1 R IVER R ESTORATION River Restoration & Biodiversity Conservation & B IODIVERSITY A DISORDER APPROACH C ONSERVATION : A Kris Van Looyv DISORDER APPROACH Central question for the research was the role played by river dynamic processes in the river ecosystem and its regulatory aspects, useful for the development of conservation and restoration strategies. These aspects were investigated in the terrestrial riverine communities of floodplain vegetation and riparian ground beetles and forests. This thesis contains a number of papers featuring a range of river restoration and biodiversity conservation topics, brought in the picture at different scales with an array of techniques and approaches for a wide variety of biotic communities, emphasized upon in habitat templets, population dynamic strategies, habitat net- works or diagnostic species. Yet, they all tell the same story of a river expressing itself in its unique setting of geomorphology, landscape and biotic features, in a non-equilibrium relation that is governed by the flow dynamics. These observations were integrated in a river disorder approach for the target setting and objective definition of the restoration and conservation strategies. Guidelines and targets were K RIS derived for local, reach or even catchment’s scale conservation strategies, based on determined responses to disorder elements of specific communities. V AN L OOY inbo phd_kv_deel1 4/18/06 3:54 PM Pagina 1 Universiteit Antwerpen River Restoration & Biodiversity Conservation A disorder approach Kris Van Looy Proefschrift voorgedragen tot het bekomen van de graad van Doctor in de Wetenschappen Promotor: Patrick Meire Co-promotor: Eckhart Kuijken phd_kv_deel1 4/18/06 3:54 PM Pagina 2 Prof. dr. Patrick Meire (Universiteit Antwerpen, promotor) Prof. dr. Eckhart Kuijken (Instituut voor natuur- en bosonderzoek, copromotor) Prof. dr. Ivan Janssens (Universiteit Antwerpen, voorzitter) Prof. dr. Stijn Temmerman (Universiteit Antwerpen) Prof. dr. Ivan Nijs (Universiteit Antwerpen) Prof. dr. Wim Van Leussen (Universiteit Twente) dr. Bas Pedroli (Alterra) 2 phd_kv_deel1 4/18/06 3:54 PM Pagina 3 ACKNOWLEDGEMENTS I want to thank all the colleagues and friends that shared thoughts, visions, ideas and joy in river restoration with me and that brought me this far. The River Meuse inspired me in this work, gave me valuable friends and brought me in many nice places, so maybe I owe her some thanks too. Special thanks goes in the first place to Geert De Blust for the enlightenment, there was always some enlightened ideas at hand right next door. Olivier Honnay for talking me into this late-night job and all the support. Of course Patrick Meire who taught me a lot, for the encouragement also and not the least for the competi- tion between Flanders’ streams, of which I had the honour to study the largest and most natural, but that discussion remains, I guess and hope. Eckhart Kuijken for the trust and the persistence to harden me. The river authority AWZ granted this research for a good part, was very cooperative in the experiments and the experiencing in the Meuse restoration efforts. The enthusiasm of Herman Gielen is not mentioned as important driver for restoration and conservation in this thesis, but it definitely is. And last but not least, Anouck, Siemen and Wannes, who make it all worth it. Acknowledgement / 3 phd_kv_deel1 4/18/06 3:54 PM Pagina 4 4 phd_kv_deel1 4/18/06 3:54 PM Pagina 5 TABLE OF CONTENTS chapter I. Introduction and outline chapter II. A conceptual framework for target setting in river restoration II.1 Setting targets for river restoration II.2 Order and disorder in the river continuum chapter III. Drivers of riparian biodiversity III.1 Effects of river embankment and forest fragmentation on species richness and composition of floodplain forest III.2 The role of river dynamics in the conservation of dry river grasslands III.3 Ground beetle habitat templets and riverbank integrity chapter IV. Thresholds and boundary conditions IV.1 Predicting riparian forest restoration IV.2 A conservation paradox for river corridor plants IV.3 Hydropeaking impact on a riparian ground beetle community chapter V. Tools for assessment and evaluation V.1 Including riparian vegetation in the definition of morphological reference conditions for large rivers; a case study for Europe’s Western Plains V.2 Dynamische voorspelling in het riviergebied V.3 Defining an ecological minimum in river restoration chapter VI. Synthesis and conclusions VI.1 Defining conservation objectives VI.2 Conclusions: The disorder approach in river restoration Samenvatting Table of contents / 5 phd_kv_deel1 4/18/06 3:54 PM Pagina 6 phd_kv_deel1 4/18/06 3:55 PM Pagina 7 I INTRODUCTION, AIMS AND OUTLINE Introduction, aims and outline / 7 phd_kv_deel1 4/18/06 3:55 PM Pagina 8 1. Introduction In two consecutive winters of the mid-nineties of the last century, the highest ever recorded peak discharges shook-up the Meuse valley and its inhabitants. A catastrophe to man, a blessing to nature; these extreme peak events revi- talised the Common Meuse. Embankments were broken up, restoring the morphological processes of the river bed over extensive stretches. In the floodplain erosion and sedimentation processes reshaped the riparian landscape that was at the same time re-colonised by a range of riverine organisms, from aquatic macroinvertebrates to plant and bird species. This revitalisation was also source of inspiration for the restoration plans and research efforts, and it worked through in the appraisal and weight for the restoration programme that was initiated some years before. These events were the starting point of our research for restoration potentials in the Flemish Meuse valley. River restoration and the natural value of river ecosystems is an increasing area of interest for management as well as research. There is an unprecedented need to preserve and restore aquatic and riparian biological diversity before extinction eliminates the opportunity (Kauffman et al. 1997). The relationship between conservation and restoration can be one of excluding or complementing each other. Here we explore the latter option, and try to determine the merits of the restoration for the biodiversity conservation. We can point at the pan-European legislative contexts and frameworks for both; the Habitat Directive aiming at the conservation of habitats and species and the Water Framework Directive oriented to the restoration of a good ecological status. In this introduction, we will review the approaches and their conceptual frameworks, and further introduce the case-study of the River Meuse. Different head- ers are the conceptual frameworks, the biodiversity approach, river disorder and the Meuse case, with its general characterisation, mapping and sampling and restoration potentials and targets. At the end, an outline to this thesis is given. 8 phd_kv_deel1 4/18/06 3:55 PM Pagina 9 1.1 Conceptual framework of conservation and restoration in river systems Conservation and restoration Conservation is both preservation and care, a dynamic process (Haslam 1996). Restoration is returning the system to a close approximation of the pre-disturbance ecosystem that is persistent and self-sustaining, though dynamic in its composition and functioning (Maurizi & Poillon 1992). Haslam pointed at the dynamics in both definitions and the ‘Sense of Place’ in his plea for preliminary thoughts and theoretical considerations, before trying to con- vert rivers to a ‘Standard Recommended’ river without sense of the unique charac- ter and special features of the river. In this context it is important to refer to a clear definition of conservation and restoration options and dimensions. At one extreme, conservation goals reflect the desire to preserve remnants of natural or near-intact systems. Far more common, however, are endeavours to rectify and repair some (or all) of the damage to river ecosystems brought about by human activities. Various terms used to describe these goals and activities can be summarized using the umbrella term “restoration”. Boon (1992) describes five appropriate strategies for river conservation or “restoration”, in accordance with the state of the river. Where few natural or semi-natural systems with untouched hydrodynamics remain, their preservation is the task. This is rare in Europe, where all large rivers are more or less controlled. For rivers with a still high ecosystem quality and with ecological key factors functioning without major impediments, there the management option is for limitation of catchment development. When the quality is low, their mitigation becomes the case and the development of existing economic and recreational functions need to be accompa- nied by the implementation of measures that allow the survival of habitats and organisms. When rivers are degraded to a point that natural hydrodynamics are hardly recognisable and only scattered and small remnants of populations persist, there the emphasis shifts towards river restoration. With the help of well chosen restoration techniques and nature development projects, more suitable habitats need to be created, enhancing the recovery of the remaining populations and the establishment of new ones (Gore 1985). The final management option mentioned Introduction, aims and outline / 9 phd_kv_deel1 4/18/06 3:55 PM Pagina 10 by Boon (1992), is for the worst case scenario where recovery is hopeless and dereliction is the only wise decision. In these cases, limited resources should not be allocated, but rather directed towards more promising restoration projects. As Boon gives 5 definitions of restoration ’dimensions’, we try to see the continuum in these terms and frequent the most commonly used term river restoration, often without regard to a historic reference, but in the broad sense of restoring/enhancing river functioning and specific river communities. In the continuum of restoration types, targets range from strong ecological goals to hard engineering erosion control and containment efforts (Giller 2005). Emphasis in our work is on the habitat restoration and biodiversity conservation scope of river restoration projects.

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