(Joint) Submission to the first Global Stocktake
Satellite-based map of global mangrove extent and changes:
Global Mangrove Watch (GMW)

The Japan Aerospace Exploration Agency (JAXA), the Institute for the Global Environmental
Strategies (IGES), Aberystwyth University, solo Earth Observation (soloEO), Wetlands International
and The Nature Conservancy, are pleased to submit an input to the Global Stocktake of the Paris
Agreement in response to the mandate of Decision 19/CMA.1, paragraph 19, 36 and 37. Thissubmission provides inputs to a cross-cutting guiding question 21 1:Summary•••••1Nature-based Solutions (NbS), including coastal and marine NbS, such as mangroves, are a
critical element of meeting the goals of the Paris Agreement for their capacity to sequester andstore vast amounts of carbon, commonly known as Blue Carbon, and prevent and minimize
coastal erosion and flooding 1.
The Global Mangrove Watch (GMW) 2 map of global mangrove extent and changes is an openaccess geospatial dataset and online tool, derived from a combination of optical and radar
satellite data, for tracking changes in mangrove spatial extent, including the progress ofmangrove conservation and restoration between the 1990’s and the present.
As such, the GMW can be used as a tool for countries that do not yet have their mangrove
monitoring systems to design, implement and track the progress of their national climate
commitments and identify opportunities to include mangroves in the next round of nationallydetermined contributions (NDCs), in support of the Paris Agreement’s long-term goals for
mitigation and adaptation.
The GMW dataset is furthermore used by UNEP to support reporting on Sustainable
Development Goals, Indicator 6.6.1 (Change in the extent of water-related ecosystems overtime) 3
The GMW dataset is provided by the Global Mangrove Watch and JAXA.

What evidence and methodologies exist for taking stock of the implementation of the Paris Agreement to assess the collective
progress towards achieving its purpose and long-term goals, including under Article 2.1(a–c), in the thematic areas of mitigation,adaptation and means of implementation and support, including on efforts to address the social and economic consequences andimpacts of response measures and efforts to enhance understanding, action and support, on a cooperative and facilitative basis,
related to averting, minimizing and addressing loss and damage associated with the adverse effects of climate change (para 6(b))?
1
https://unfccc.int/sites/default/files/resource/Scopingpaper_Finalest%20version.pdf
2
The Global Mangrove Watch (GMW) is a partnership between Aberystwyth University, solo Earth Observation, Wetlands
International and The Nature Conservancy, established in 2011 as part of JAXA’s Kyoto & Carbon Initiative3
https://www.sdg661.app

The Global Mangrove Watch interactive website platform (globalmangrovewatch.org)(Yellow: countries/territories with mangroves; Green: mangrove extent)

1. The importance of mangroves within the first Global Stocktake
Coastal and marine ecosystems such as mangroves have been historically overlooked within
UNFCCC processes, despite their importance and the recognition of their potential in the ParisAgreement. Mangroves and other coastal “Blue Carbon” ecosystems, which also include e.g.
saltmarshes and seagrass beds, have exceptional capacity to sequester and store carbon, andprovide protection for coastal communities to mitigate the impacts of climate change.
For the GST to comprehensively assess progress on meeting the goals of the Paris Agreement,each of its three components, including submissions of inputs from countries and otherstakeholders, must reflect the key role of Nature-based Solutions (NbS) and coastal and marine
ecosystems for climate action. The GST can help assess progress and provide an understanding ofwhat is needed for NbS to fully harness the potential of nature-based solutions in the next roundof national climate commitments and near-term international support.
2. Global Mangrove Watch dataset usage
The GMW dataset, described in further detail below, can be used as a tool for countries that do
not yet have their own mangrove monitoring systems for taking stock and assessing their progress
towards achieving international commitments regarding mangroves and identifying opportunities
of including mangroves in their NDCs.
National or regional data on changes (gains and losses) in mangrove extent can be estimated andused as evidence to assess the collective progress in efforts towards adaptation and mitigation. Inparticular, increase in mangrove areas can help prevent and minimize coastal erosion and flood
damage, and thus contribute to progress in efforts towards adaptation. The GMW change maps
can furthermore be used to estimate CO2 removals following the methods provided in Chapter 4of the “2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories:
Wetlands” (IPCC, 2014) in combination with e.g., IPCC default data or available local or global
maps of mangrove above-ground biomass (such as e.g. the global dataset by Simard et al., 2019),
and thus demonstrate progress in efforts towards mitigation.
3. Methodology
The mangrove maps (GMW v3.0) were derived in two steps: (1) Generation of a baseline map ofglobal mangrove extent for the year 2010, and, (2) Detection of changes between the 2010 baseline
and each of the other years, respectively. A combination of optical and radar satellite data wasused. Optical sensors are useful to distinguish mangroves from other types of vegetation, whileradar sensors, which are unaffected by cloud cover and sensitive to changes in structure, wereused to map changes throughout the time-series.
The 2010 baseline map was derived through a Random Forest classification of optical (primarilyLandsat) satellite data. The classification was confined within a mangrove habitat mask, which
defines the biogeographical range where mangrove ecosystems can be expected to exist(notwithstanding human influence). The mangrove habitat definition was based on geographicalparameters such as latitude, elevation, distance from ocean water, as well as historical open surface
water occurrence. Training for the mangrove classification was based on random sampling fromhistorical maps of mangroves.
The classification accuracy of the 2010 baseline dataset was assessed with more than 50,000
randomly sampled points across 60 randomly selected regions globally. The overall accuracy wasestimated to be 95.0% (Kappa coefficient 0.901).
The mangrove maps for the non-baseline years were subsequently derived by detection of changes(both gains and losses) relative to the 2010 baseline map using radar (JERS-1 SAR, ALOSPALSAR and ALOS-2 PALSAR-2) satellite data. The change pixels for each year were then addedor removed from the baseline map. The classification accuracy for the change maps is currently
under assessment (February 2022).
Detailed descriptions of the Global Mangrove Watch baseline and change maps development andaccuracy assessments are available in Bunting et al. (2018; 2022)
NOTE. While the GMW dataset constitutes the most comprehensive dataset of mangrove
geospatial extent and changes currently available, users are advised to keep in mind that it a
global-scale dataset, generated with a single methodology applied over all regions, and as such,the accuracy of the map may vary between locations and with scale.

4. Technical Characteristics
Spatial resolution

25 m

Recommended minimum mapping unit

1 ha(MMU)
Geographical coverage

Global (all countries with mangroves)Temporal coverage

1996, 2007, 2008, 2009, 2010 (baseline year),annual data 2015-2020

Update frequency

Annual (subsequently from 2021)

FormatGIS shapefile (.shp), geocoded raster (Geotiff),numerical statistics (.csv)

Data Policy

Public open (Creative Commons CC BY 4.0)

5. Contacts and data access
Contact:
Osamu Ochiai, Japan Aerospace Exploration Agency: ochiai.osamu@jaxa.jp
Technical contact:
Ake Rosenqvist, Global Mangrove Watch: ake.rosenqvist@soloEO.com
Associated Guidance and User Manual:Global Mangrove Watch Platform: www.globalmangrovewatch.org
Web address for dataset download:
UNEP-WCMC (vector data): https://data.unep-wcmc.org/datasets/45
JAXA (raster data): https://www.eorc.jaxa.jp/ALOS/en/dataset/gmw_e.htm
6. References
Bunting P., Rosenqvist A., Lucas, Hilarides L., Thomas N. (2022). “Global Mangrove Watch:
Updated 2010 Mangrove Forest Extent (v2.5)”. Remote Sensing (under review, Jan. 2022).
Bunting P., Rosenqvist A., Lucas R., Rebelo L-M., Hilarides L., Thomas N., Hardy A., Itoh T.,
Shimada M., Finlayson C.M. (2018). “The Global Mangrove Watch – a New 2010 GlobalBaseline of Mangrove Extent”. Remote Sensing, 2018, 10, 1669, doi.org/10.3390/rs10101669.
IPCC (2014). 2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas
Inventories: Wetlands, Hiraishi, T., Krug, T., Tanabe, K., Srivastava, N., Baasansuren, J., Fukuda,M. and Troxler, T.G. (eds). Published: IPCC, Switzerland.