1. The Global Mangrove Watch (GMW)
Takeo Tadono (JAXA)
Ake Rosenqvist (JAXA/soloEO)
Pete Bunting (Aberystwyth Univ.)
Richard Lucas (Aberystwyth Univ.)
Lisa Maria Rebelo (Int’l Water Management Inst.)
Lammert Hilarides (Wetlands International)
Nathan Thomas (NASA GSFC)
Max Finlayson (Charles Sturt Univ)
Chris McOwen (UNEP-WCMC)
Takuya Itoh (RESTEC)

2. Global Mangrove Watch
An international collaborative project established as part of the Japan Aerospace Exploration Agency (JAXA) Kyoto & Carbon (K&C) Initiative science program.
Technical leads: Aberystwyth U. (U.K.) & soloEO (Japan)
Aim to provide geospatial (map) information about mangrove extents and changes at national to global scales for Ramsar Contracting Parties, NGO’s and the public
GMW part of STRP WP Task 1.1 and the GEO-Wetlands Initiative plan to develop a Global Wetlands Observation System (GWOS)
Potential for SDG6.6.1 reporting on wetlands extents (national-global)

3. Objectives:
Overall: Mapping of extent and changes in global mangrove areas using satellite data at 25m-30m spatial resolution
Generation of updated baseline maps of the global mangrove extent for the year 2010
Generation of maps of annual changes in the global mangrove areas (at present 7 time epochs between 1996 and 2017).

4. Existing global mangrove datasets
USGS 2000 (Giri, 2010): First global baseline - derived from Landsat (optical) satellite data. Baseline now 15 years old ( ).
World Atlas of Mangroves (Spalding, 2010): Compiled from different data sets. Inconsistent across countries.
World Forest Watch (Hansen et al): does not distinguish mangrove from other types of forest

5. Satellite Radar (JERS-1, ALOS PALSAR, ALOS-2 PALSAR-2): acquisitions regardless of clouds, smoke and haze. Sensitive to vegetation structure and changes.
Satellite Optical (Landsat): Sensitive to distinction of mangrove / non-mangrove.
Increase prio 1 polygon from N60 to N70 deg
JAXA radar mosaic data available for public download at 5

6. Datasets used 1996: JERS-1 SAR 1998/2000: USGS (Giri et al) and
World Mangrove Atlas (Spalding at al)
2007–2009 : ALOS PALSAR
2010: ALOS PALSAR & Landsat-7
2015–2016 ALOS-2 PALSAR-2

7. Methodology Analysis undertaken in the RSGISLib software
( and associated python modules.

8. Challenge – many different types of changes
Losses
Aquaculture
Oil and gas exploration
Urbanization and infrastructure
Logging for firewood and other uses
Degradation
Climate change…
Gains
Natural migration
Seaward expansion (natural / anthropogenic)
Inland expansion (e.g. due to sea level rise and flooding)
Large-scale replanting projects

9. Anthropogenic changes: Aquaculture and infrastructure
Input: Multi-temporal radar image tiles
Output: Mangrove extent and change map

10. 2010 global mangrove extent Baseline (v2.0) completed
Status October 2018
2010 global mangrove extent Baseline (v2.0) completed
Classification accuracy was assessed with over 53,800 randomly sampled points across 20 randomly selected regions.
Overall accuracy %
Omission error: 2.5%
Commission error: 6.0%
Global mangrove extent (and changes rel. to 2010) completed. Validation ongoing.

11. Global 2010 baseline available for viewing and free download
Online viewing:
Download: data.unep-wcmc.org/datasets/45

12. Transparency and open data
All satellite data, classification algorithms and software and mangrove maps utilized in GMW is open and free of charge.
Mangrove maps
25m satellite radar image tiles
30m optical data
JRC water occurrence dataset
SRTM elevation data
Classification software (open source: RSGISLib.org)
Users are able to use the maps “as generated by GMW”, or access the original satellite data, classification software to replicate, validate, or improve the mangrove classifications.

13. Data availability and References
The 2010 GMW baseline is available for free public download at the UNEP-WCMC Ocean Data Viewer:
Online viewing: (select “Mangroves” in “Land Cover” menu)
GMW maps for 1996, 2007, 2008, 2009, 2015 and 2016 will be made available for viewing and download after validation has been completed (Q1 2019).
References:
Bunting P., Rosenqvist A., Lucas R., Rebelo L-M., Hilarides L., Thomas N., Hardy A., Itoh T., Shimada M. and Finlayson C.M. (2018). The Global Mangrove Watch – a New 2010 Global Baseline of Mangrove Extent. Remote Sensing, 2018, 10, 1669; doi: /rs
Global Mangrove Watch (2018).
JAXA K&C www: