Topic E1. Mangroves and Sea Level Rise Richard MacKenzie and Dan Friess Topic E1. Slide 2 of 27 Mangroves and Sea Level Rise Introduction • • Global threats to mangrove forests • • Deforestation for aquaculture, charcoal production, or development Climate change Mechanisms that have allowed mangroves to keep up with SLR in the past, present and future • • Current rates of sea level rise Forecasted rates of sea level rise Accretion rates Ability of wetlands to migrate inland Monitoring wetlands for resilience to SLR • • Rod surface elevation tables Naturally occurring radionuclides Topic E1. Slide 3 of 27 Mangroves provide many ecosystem services 1. Supporting 3. Provisioning 5. Cultural 2. Biological 4. Regulating Topic E1. Slide 4 of 27 Mangrove and Distribution in 2005 25-30o N 25-30o S Globally: 15,200,000 – 17,000,000 ha 20-35% loss since the 1980’s (FAO 2003, 2007) Topic E1. Slide 5 of 27 Climate change: sea level rise 1) Sea-level rise has nearly doubled since 1990 (5.4 cm at 3.2 mm/yr) 2) Sea-level is predicted to increase by 75-190 cm by 2100 Topic E1. Slide 6 of 27 Satellite altimetry reveals that sea-level rise is not constant across the world http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/ Topic E1. Slide 7 of 27 Under some SLR scenarios, mangrove will be progressively lost in Southeast Australia (modified from Oliver et al. 2012) Topic E1. Slide 8 of 27 So why does SLR impact mangroves? Topic E1. Slide 9 of 27 Sea-level Rise → Mangroves Sedimentation rate (mm yr-1) 14 12 10 8 6 Sedimentation rate = sea-level rise 4 2 Modified from Alongi 2008 0 0 2 4 6 8 10 12 Sea level rise (mm yr-1) Majority of mangroves are currently keeping up with sea-level rise Topic E1. Slide 10 of 27 Sea-level Rise → Mangroves Forces mangroves to retreat landwards but success of migration depends on multiple factors. Topic E1. Slide 11 of 27 Image from Google Earth, modified by R. MacKenzie. Topic E1. Slide 12 of 27 Sea-level Rise → Mangroves • If mangrove forest floor rises at rates that equal SLR, then mangroves can be maintained What makes a mangrove forest floor rise? 1) Below ground root growth 2) Healthy sediment inputs 3) Leaf litter inputs Topic E1. Slide 13 of 27 Sea-level Rise → Mangroves • If the rate of SLR is greater than the rate at which the mangrove forest floor rises, then some rearrangement of vegetation will take place or loss of mangrove will occur What makes a forest floor fall? 1) 2) 3) 4) Changes in sediment loads Changes in nutrient loads Changes in hydrology Cutting trees Topic E1. Slide 14 of 27 Sea-level Rise → Mangroves Krauss et al. 2010 Topic E1. Slide 15 of 27 Sea-level Rise → Mangroves • If the rate of SLR is greater than the rate at which the mangrove forest floor rises, then some rearrnagement of vegetation will take place or loss of mangrove will occur What makes a forest floor fall? 1) Cutting trees or less healthy trees kills below ground roots or slows their growth 2) Too much or too little sediment 3) High nutrient input can cause roots to decompose Topic E1. Slide 16 of 27 Pacific Sea Level Rise Monitoring Network 1) Identify and protect critical areas naturally positioned to survive climate change 2) Establish baseline data and monitor the responses of mangroves to climate change Topic E1. Slide 17 of 27 Mangrove forest floor elevation 1) Rod surface elevation tables (rSETS) Krauss et al 2010 Topic E1. Slide 18 of 27 measurement at time point 1 Topic E1. Slide 19 of 27 measurement at time point 2 Topic E1. Slide 20 of 27 Mangrove forest floor elevation 2) Radionuclides Naturally occurring radionuclide: 222Ra 222Ra 210Pb 210Pb Topic E1. Slide 21 of 27 Topic E1. Slide 22 of 27 Where are we monitoring? Topic E1. Slide 23 of 27 Summary • Sea level rise is the climate change phenomena that is expected to have the greatest negative impact on mangrove forests • Sea level rise will result in shifts in the distribution of mangroves species or the ultimate loss of species and wetland ecosystems and thus the many ecosystem services that they provide. • Mangroves are resilient ecosystems and in many places appear to be keeping up with current rates of SLR, this is due to belowground root growth and health sedimentation rates • Mangroves in environments characterized by sediment deficits, low groundwater tables, and erosion are thought to be the most sensitive to SLR. • Mangrove vulnerability and resilience to relative sea-level rise largely depend on mangrove sediment surfaces, species composition and ability of different species to colonize new habitats, the slope of the adjacent land relative to that of the land that the mangroves currently occupy and the presence of obstacles that can impede landward migration, and the effects of other stressors (e.g., pollution, overharvesting). Topic E1. Slide 24 of 27 References Alongi DM. 2008. Mangrove forests: Resilience, protection from tsunamis, and responses to global climate change. Estuarine, Coastal and Shelf Science 76:1-13. [FAO]Food and Agriculture Organization of the United Nations. 2003. Status and trends in mangrove area extent worldwide. By Wilkie, M.L. and Fortuna, S. Forest Resources Assessment Working Paper No. 63. Forest Resources Division. Rome: FAO. [FAO]Food and Agriculture Organization of the United Nations. 2007. The world’s mangroves 1980– 2005. FAO Forestry Paper 153. Rome: FAO. Field CD. 1995. Impact of expected climate change on mangroves. Hydrobiologia 295:75-81. Gilman EL, Ellison J, Duke NC, and Field CB. 2008. Threats to mangroves from climate change and adaptation options: A review. Aquatic Botany 89:237-250. Krauss KW, Cahoon DR, Allen JA, Ewel KC, Lynch JC, and Cormier N. 2010. Surface elevation change and susceptibility of different mangrove zones to sea-level rise on Pacific high islands of Micronesia. Ecosystems 13:129-143. Topic E1. Slide 25 of 27 References Krauss KW, McKee KL, Lovelock CE, Cahoon DR, Saintilan N, Reef R, and Chen L. 2014. How mangrove forests adjust to rising sea level. New Phytologist 202:19-34. McLeod E and Salm RV. 2006. Managing Mangroves for Resilience to Climate Change. Gland, Switzerland. Merrifield MA, Merrifield ST, and Mitchum GT. 2009. An anomalous recent acceleration of global sea level rise. Journal of Climate 22:5772-5781. Oliver TSN, Rogers K, Chafer CJ, and Woodroffe CD. 2012. Measuring, mapping and modelling: an integrated approach to the management of mangrove and saltmarsh in the Minnamurra River estuary, southeast Australia. Wetland Ecology and Management 20:353-371. Semeniuk V. 1994. Predicting the Effect of Sea-Level Rise on Mangroves in Northwestern Australia. Journal of Coastal Research 10:1050-1076. Topic E1. Slide 26 of 27 References Solomon S, Qin D, Manning M, Alley RB, Berntsen T, Bindoff NL, Chen J, Chidthaisong A, Gregory JM, Hegerl GC, et al. 2007. Technical Summary, Climate Change 2007: The Physical Science Basis. In Solomon S, Qin D, Manning M, Marquis M, Averyt KB, Tignor M, Miller H, and Chen Z (eds.). Contribution of Working Group 1 to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK:Cambridge University Press. 19-91. Tomlinson PB. 1986. The Botany of Mangroves. Cambridge University Press, Cambridge, UK. Vermeer M and Rahmstorf S. 2009. Global sea level linked to global temperature. Proceedings of the National Academy of Sciences of the United States of America 106:21527-21532. Webb EL, Friess DA, Krauss KW, Cahoon DR, Guntenspergen GR, and Phelps J. 2013. A global standard for monitoring coastal wetland vulnerability to accelerated sea-level rise. Nature Climate Change 3:458-465. Thank you The Sustainable Wetlands Adaptation and Mitigation Program (SWAMP) is a collaborative effort by CIFOR, the USDA Forest Service, and the Oregon State University with support from USAID. How to cite this file MacKenzie R and Friss D. 2015. Mangroves and sea-level rise [PowerPoint presentation]. In: SWAMP toolbox: Theme E section E1 Retrieved from www.cifor.org/swamp-toolbox> Photo credit Daniel Donato, Daniel Murdiyarso/CIFOR, Neil Palmer/CIAT, Rich MacKenzie/USFS, Rupesh/CIFOR.