Global Mangrove Watch¶

This study has used L-band Synthetic Aperture Radar (SAR) global mosaic datasets from the Japan Aerospace Exploration Agency (JAXA) for 11 epochs from 1996 to 2020 to develop a long-term time-series of global mangrove extent and change. The study used a map-to-image approach to change detection where the baseline map (GMW v2.5) was updated using thresholding and a contextual mangrove change mask. This approach was applied between all image-date pairs producing 10 maps for each epoch, which were summarised to produce the global mangrove time-series. The resulting mangrove extent maps had an estimated accuracy of 87.4 % (95^th conf. int.: 86.2 - 88.6 %), although the accuracies of the individual gain and loss change classes were lower at 58.1 % (52.4 - 63.9 %) and 60.6 % (56.1 - 64.8 %), respectively.

Sources of error included a mis-registration in the SAR mosaic datasets, which could only be partially corrected for, but also confusion in fragmented areas of mangroves, such as around aquaculture ponds. Overall, 152,604 km2 (133,996 - 176,910) of mangroves were identified for 1996, with this decreasing by -5,245 km2 (-13,587 - 3686) resulting in a total extent of 147,359 km2 (127,925 - 168,895) in 2020, and representing an estimated loss of 3.4 % over the 24-year time period. The Global Mangrove Watch Version 3.0 represents the most comprehensive record of global mangrove change achieved to date and is expected to support a wide range of activities, including the ongoing monitoring of the global coastal environment, defining and assessments of progress towards conservation targets, protected area planning and risk assessments of mangrove ecosystems worldwide.

You can download the dataset here and read the paper here

Disclaimer: Whole or parts of the dataset description were provided by the author(s) or their works.

Preprocessing¶

Raster tiles were mosaiced so that all extents and allied rasters can fit into single collections. Date ranges were added later to the raster and the vector layers.

Citation:¶

Bunting, P.; Rosenqvist, A.; Hilarides, L.; Lucas, R.M.; Thomas, T.; Tadono, T.; Worthington, T.A.; Spalding, M.; Murray, N.J.; Rebelo, L-M. Global
Mangrove Extent Change 1996 – 2020: Global Mangrove Watch Version 3.0. Remote Sensing. 2022

Dataset citation¶

Bunting, Pete, Rosenqvist, Ake, Hilarides, Lammert, Lucas, Richard, Thomas, Nathan, Tadono , Takeo, Worthington, Thomas, Spalding , Mark, Murray,
Nicholas, & Rebelo, Lisa-Maria. (2022). Global Mangrove Watch (1996 - 2020) Version 3.0 Dataset (3.0) [Data set]. Zenodo. https://doi.org/10.5281/
zenodo.6894273

gmw_small

Earth Engine Snippet: Extent¶

var extent_raster = ee.ImageCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/GMW_V3");
var extent_1996 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_1996_vec");
var extent_2007 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2007_vec");
var extent_2008 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2008_vec");
var extent_2009 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2009_vec");
var extent_2010 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2010_vec");
var extent_2015 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2015_vec");
var extent_2016 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2016_vec");
var extent_2017 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2017_vec");
var extent_2018 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2018_vec");
var extent_2019 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2019_vec");
var extent_2020 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/extent/gmw_v3_2020_vec");

Earth Engine Snippet: Change from 1996¶

var change_f1996_raster = ee.ImageCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/change_f1996");
var change_f1996_2007 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2007_vec");
var change_f1996_2008 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2008_vec");
var change_f1996_2009 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2009_vec");
var change_f1996_2010 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2010_vec");
var change_f1996_2015 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2015_vec");
var change_f1996_2016 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2016_vec");
var change_f1996_2017 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2017_vec");
var change_f1996_2018 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2018_vec");
var change_f1996_2019 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2019_vec");
var change_f1996_2020 = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/change/gmw_v3_f1996_t2020_vec");

Earth Engine Snippet: Union¶

Single layer of pixels which were mangroves at any date in the time series

var gmw_union_raster = ee.Image("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/union/gmw_v3_mng_union");
var gmw_union_vector = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/union/gmw_v3_union_vec");

Earth Engine Snippet: Core¶

Single layer of pixels which were mangroves at all dates within the time series

var gmw_core_raster = ee.Image("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/core/gmw_v3_mng_core");
var gmw_core_vector = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/core/gmw_v3_core_vec");

Earth Engine Snippet: Tiles¶

Vector layer with the 1x1 degree tiles used for the analysis

var tiles = ee.FeatureCollection("projects/earthengine-legacy/assets/projects/sat-io/open-datasets/GMW/gmw_v3_tiles");

Resolution: approx 30m

Global Mangrove Watch: Annual Mangrove Extent 4.0.19¶

To improve the resolution and local relevance of the Global Mangrove Watch (GMW) baseline, a new layer has been created for 2020. Using Copernicus Sentinel-2 satellite imagery, processed to a pixel resolution of 10 m, the mangrove extent has been completely remapped and revised with many areas which were not previously mapped now included within the new map. This has increased the spatial resolution of the mapping from a pixel resolution of 25 m to 10 m, allowing finer features to be mapped, such as fringing and riverine mangroves.

Earth Engine Snippet: Sentinel Raster and Vector Baseline v4.0.19¶

//Extent v4.0.19
var raster_extent = ee.ImageCollection("projects/sat-io/open-datasets/GMW/annual-extent/GMW_MNG_2020");
var vector_extent = ee.FeatureCollection("projects/sat-io/open-datasets/GMW/annual-extent/GMW_MNG_VEC_2020");
Map.addLayer(raster_extent.median(),{"opacity":1,"bands":["b1"],"min":1,"max":1,"palette":["228B22"]},'GMW Raster Extent 2020  v4.0.19')
Map.addLayer(ee.Image().paint(vector_extent,0,3), {"palette":["red"]}, 'GMW Vector Extent 2020 v4.0.19')