Ecological questions in resilient coastal defence

Transcription

1 Koninklijk Royal Netherlands Nederlands Institute Instituut for Sea voor Research Zeeonderzoek The New Coast Ecological questions in resilient coastal defence Peter M.J. Herman + Spatial Ecology team at NIOZ-Yerseke NIOZ Radboud University

2 km

3 Subsidence in world deltas Syvitski et al Nat.Geosci.

4 Megacities endangered by drowning (2070) Estuarine ecosystem Coastal ecosystem + engineering Dune ecosystem Hard engineering Temmerman et al. 2013, Nature

5 200 BC First openings in coastline People start draining bogs for agriculture 350 AD Whole area drowned Consequence of extensive drainage in Roman times

6 Age of Polders Height map of Zeeland

7 Rotterdam Rotterdam Haringvliet Grevelingen Oosterschelde Veerse Meer Volkerak/ Zoommeer Zeebrugge Westerschelde Ghent Antwerp Antwerp Cities Harbours Dams Freshwater Estuarine gradient Salt lake Salt sea-arm

8 Zeeland s extremely closed coast: Engineered: calculated uncertainty Controlled persistence of structures Space-efficient Low resilience: subsidence does not follow SLR strong setup Ecological deterioration: connectivity (nutrients, species, sand, salt, C,..) habitat loss;

9 The new coast Soft, connected, dynamic Minimal (but essential) engineering Requires space + trust in natural processes Temmerman et al. 2013, Nature

10 Technical approaches broad green dike with marsh foreland Sand motor Depoldering Double dike with sedimentation area in between

11 The broad green dike with marsh foreland Groene dijk Bron: Pilotstudie Groene Dollarddijk, van Loon & Schelfhout, 2013

12 Zandmotor photo Rijkswaterstaat Hedwigepolder VNSC.eu

13 Ecological questions Where to expect physical-biological self-organisation Scales in time, space Persistence of ecosystems over decadal time scales Stochasticity: Performance in extreme conditions Mechanisms of decay / regeneration

14 Biogeomorphic systems

15 Ecosystem Engineering Biota Physics STRONG hydrodynamics REDUCED hydrodynamics Organisms that modify the abiotic environment by their biological activity (Jones 1994)

16 Questions When/where important for system state and dynamics? What determines persistence? Can it be used for coastal defense? Biota Physics?? Stress / Disturbance

17 Biological effects on sand waves? ν T E, D L. conchilega T. fabula E. cordatum Borsje et al., 2009 Borsje et al., 2014, JGR MESH T. van Dijk TNO (NL)

18 Effects on sand waves Animals No Animals Borsje et al Ocean Dyn.

19 Small changes large areas PnO P O

20 Diatom patterns on Kapellebank Diatoms + + Sediment Diatoms - - Sediment Facilitation Negative feedback Weerman et al Am. Nat.

21 Diatom patterns on Kapellebank Chlorophyll-a concentration (µg g -1 ) Diatoms Grazers * ` Arrival of Macoma balthica 0 3/28 4/11 4/25 5/9 5/23 6/6 Macrofana abundnce (ind m -2 ) Date Weerman et al.2010 Am.Nat.; 2011 Ecology

22 Commensurate forces Development of biogeomorphic system when physical and biological forces of similar strength vegetation Intensity of disturbance

23 Non-spatial ASS -> spatial self-organisation Upper water layer Lower water layer current Input Algae Mussels Uptake 1000 m Van de Koppel et al., Am. Nat. 2005

24 Structures at different scales Large scale Small scale 1000 meter 1 meter Van de Koppel et al Am.Nat / 2008 Science

25 Multi-scale complexity adds to resilience example from mussel bed self organisation Liu et al Nat.comm.

26 Large-range extended effects between systems example mussels and cockles Van de Koppel et al Ann. Rev. Mar. Sci. Based on Donadi et al Ecology

27 Self-organisation at landscape scale? Van de Koppel et al Ann. Rev. Mar. Sci. Based on Gillis et al MEPS

28 Stochasticity Coastal protection only relevant at exceptionally rough conditions does wave damping etc. hold? Is ecosystem persistent at time scale of coastal protection measures (decades) How do alternative states change (appearance/disappearance) Cyclicity?

29 Wave attenuation by marshes: also works under extreme conditions 330 m long, 7 m deep, 5 m wide Moller et al., Nat. Geosc. 2014

30 Wave attenuation by marshes: also works under extreme conditions 330 m long, 7 m deep, 5 m wide Moller et al., Nature Geosc. 2014

31 Moller et al., Nature Geosc. 2014

32 Establishment of saltmarsh plants

33 Role of stochasticity in biogeomorphology Balke et al J. Ecol.

34 Saltmarshes Westerschelde RWS Balke et al J. Ecol.

35 Conclusions Our coasts have been formed during the anthropocene It is our task to preserve coastal resilience for Safety Ecosystem services The new, soft coast requires better ecological understanding Self-organisation processes Resilience as a function of complexity Stochastic events (creation / destruction) Long-term integrity and/or recovery Better ecology will integrate better with building with nature