Topic E1. Mangroves and Sea Level Rise

Richard MacKenzie and Dan Friess

Introduction• Current rates of sea level rise• Forecasted rates of sea level rise

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• Accretion rates• Ability of wetlands to migrate inland

Monitoring wetlands for resilience to SLR • Rod surface elevation tables• Naturally occurring radionuclides

Mangroves and Sea Level Rise

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Mangroves provide many ecosystem services1. Supporting 3. Provisioning

2. Biological 4. Regulating

5. Cultural

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Mangrove and Distribution in 2005

25-30o N

25-30o S

Globally: 15,200,000 – 17,000,000 ha20-35% loss since the 1980’s

(FAO 2003, 2007)

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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

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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/http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/

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(modified from Oliver et al. 2012)

Under some SLR scenarios, mangrove will be progressively lost in Southeast Australia

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So why does SLR impact mangroves?

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Sea level rise (mm yr-1)

0 2 4 6 8 10 12

Sed

imen

tati

on

rat

e (m

m y

r-1 )

0

2

4

6

8

10

12

14

Majority of mangroves are currently keeping up with sea-level rise

Sea-level Rise → Mangroves

Modified from Alongi 2008

Sedimentation rate = sea-level rise

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Forces mangroves to retreat landwards but success of migration depends on multiple factors.

Sea-level Rise → Mangroves

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Image from Google Earth, modified by R. MacKenzie.

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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 growth2)Healthy sediment inputs3)Leaf litter inputs

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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)Changes in sediment loads2)Changes in nutrient loads3)Changes in hydrology4)Cutting trees

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Sea-level Rise → Mangroves

Krauss et al. 2010

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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 growth2)Too much or too little sediment3)High nutrient input can cause roots to decompose

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Pacific Sea Level Rise Monitoring Network

1) Identify and protect critical areas naturally positioned to survive climate change2) Establish baseline data and monitor the responses of mangroves to climate change

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Mangrove forest floor elevation

1) Rod surface elevation tables (rSETS)

Krauss et al 2010

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measurement at time point 1

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measurement at time point 2

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222Ra

222Ra 210Pb

Naturally occurring radionuclide: 210Pb

Mangrove forest floor elevation

2) Radionuclides

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Where are we monitoring?

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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 sedimentationrates

• 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).

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ReferencesAlongi 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.

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ReferencesKrauss 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.

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ReferencesSolomon 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.

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 fileMacKenzie 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 creditDaniel Donato, Daniel Murdiyarso/CIFOR, Neil Palmer/CIAT, Rich MacKenzie/USFS, Rupesh/CIFOR.

Thank you