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DSD-INT 2019 Mangrove diversity loss may be inevitable - Xie


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Presentation by Danghan Xie, University of Utrecht, The Netherlands, at the Delft3D and XBeach User Day: Coastal morphodynamics, during Delft Software Days - Edition 2019. Wednesday, 13 November 2019, Delft.

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DSD-INT 2019 Mangrove diversity loss may be inevitable - Xie

  1. 1. Credit by Artist: Yuhau Fang, China, Age 9Credit by Artist: A. Basheer, India, 9th Grade Danghan Xie(1), Christian Schwarz(1), Muriel Z.M. Brückner(1), Maarten G. Kleinhans(1), Dunia H. Urrego(2), Zeng Zhou(3) & Barend van Maanen(1,2) (1) Faculty of Geosciences, Utrecht University, Utrecht, Netherlands (2) College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom (3) College of Harbour, Coastal and Offshore Engineering, Hohai University, Nanjing, China under sea level rise and human pressure Mangrove diversity loss may be inevitable
  2. 2. Mangroves – A multifunctional coastal ecosystem • Biodiversity reserves and organisms’ habitats. • Coastal protection from natural hazards • Water and air purifier • Carbon storage and sequestration • Food production (fish, shell fish and algae) • A source for food, medicine and fuelwood • Tourist and recreation Photo credit by: `Photo credit by: ieyenews 2
  3. 3. Climate change and human actions – 2 potential threats 3
  4. 4. Sea level rise Phan et al. (2015) Human infrastructure • How do mangrove forests respond to different combinations of sea level rise rates, sediment supplies, and the presence of barriers? Climate change and human actions – 2 potential threats Photo credit by: Qian Zhang Sediment supply limitation 3
  5. 5. White mangrove Black mangrove SLR Sediment deposition/erosion Multiple mangrove species Sediment supply Sediment transport MWL Red mangrove Schematic of 1D eco-morphodynamic model: Comprehensive treatment of sediment transport processes: Erosion/deposition and transport of sediment between regions Multiple mangrove species: Dynamic growth of red, black and white mangroves Human barriers: Barriers are incorporated in the model, restricting the upland movement of water and vegetation 4
  6. 6. Coco et al. (2013) Delft3D Matlab Mangrove model from van Maanen et al. (2015) Vegetation model from van Oorschot et al. (2016) Saltmarsh model from Brückner et al (submitted) Vegetation model based on: Working structure of eco-morphodynamic model: 5
  7. 7. Coco et al. (2013) Delft3D Matlab Working structure of eco-morphodynamic model: Vegetation life processes: Colonization, growth and mortality 5
  8. 8. Coco et al. (2013) Delft3D Matlab Working structure of eco-morphodynamic model: Vegetation life processes: Colonization, growth and mortality 5
  9. 9. Coco et al. (2013) Delft3D Matlab Working structure of eco-morphodynamic model: Fitness and competition 5 white black red Mangrove: Modified from Krauss et al. (2008) van Maanen et al. (2015)
  10. 10. Mangrove assemblage diversity index (ADI): 6 1. richness 2. evenness 𝐴𝐷𝐼 = − ෍ 𝑖=1 𝑛 𝑝𝑖 ∙ ln 𝑝𝑖 where 𝑝𝑖 is the proportional extent of species i relative to the total forest extent.
  11. 11. Low SSC High SLR All mangrove species shift to upland Mangroves expand to both seaward and landward High SSC Low SLR Year 30, 100, 200, 300 * SSC= Sediment supply concentration; SLR=sea level rise Impacts of sediment supply concentration and sea level rise time 7
  12. 12. Low SSC High SLR High SSC Low SLR I am a dyke… Extinction of white mangrove All mangrove species shift to upland, extinction happens Mangroves expand to seaward but blocked on upland Impacts of human barriers Loc.1 Loc.2 Loc.3 8
  13. 13. Bed level accumulation rate decreases while inundation period increases → species are linked!!! 9 Impacts of human barriers High SSC Low SLR
  14. 14. Barriers play a role in promoting vertical accretion! Movement of seaward forest edge averaged over 300 years With barriersWithout barriers Retreat Expansion Retreat Expansion 10 Retreat Expansion
  15. 15. Movement of the seaward forest edge may reverse! With barriersWithout barriers Temporal evolution of the seaward forests edge Continuous retreat 11 Continuous expansion Continuous retreat Shifts Continuous expansion Shifts: (Retreat to expansion Expansion to retreat)
  16. 16. Losses in mangrove diversity with rising sea level might be inevitable! With barriersWithout barriers Changes of mangrove assemblage diversity in 300 years 12 Species loss Species unevenness
  17. 17. Forest extent can increase under high SSC despite SLR, but it does not necessarily mean an increase in diversity. Questions? Barriers may enhance sediment accretion but obstruct mangrove landward migration, potentially causing extinction of species. Mangrove species are linked through complex biophysical interactions and play a critical role in defining forest structural changes. Sediment accretion across the intertidal area may vary over time… (historical/current accretion rates may be misleading). Key messages 13 Danghan Xie | PhD Candidate | Utrecht University |