OHI Science | Citation policy
This script generates the extent of saltmarsh for each OHI region.
Creating an actual script to calculate this. This has not been updated since 2012. Updating the data with newest version (version 6).
Downloaded: 07/25/2019
Description:
Global Distribution of Saltmarshes https://data.unep-wcmc.org/datasets/43 Reported at spatial cell scale.
This dataset displays the extent of our knowledge regarding the distribution of saltmarsh globally, drawing from occurrence data (surveyed and/or remotely sensed).
Time range: 1973-2015
Reclassify the saltmarsh extent data into a mask of 1 or NA, and then compute zonal statistics for the count of cells within an OHI region that have saltmarsh and then convert into km2.
## This file makes it easier to process data for the OHI global assessment
## by creating the following objects:
##
## * dir_M = identifies correct file path to Mazu (internal server) based on your operating system
## * mollCRS = the crs code for the mollweide coordinate reference system we use in the global assessment
## * regions_shape() = function to load global shapefile for land/eez/high seas/antarctica regions
## * ohi_rasters() = function to load two rasters: global eez regions and ocean region
## * region_data() = function to load 2 dataframes describing global regions
## * rgn_syns() = function to load dataframe of region synonyms (used to convert country names to OHI regions)
## * low_pop() = function to load dataframe of regions with low and no human population
## * UNgeorgn = function to load dataframe of UN geopolitical designations used to gapfill missing data## loads 2 rasters: zones and ocean
## zones = raster cells with OHI region ID values, see rgns_all.csv to link IDs with names
## ocean = raster with ocean cells identified as 1, otherwise 0## returns spatial shape object named 'regions'
## which includes land, eez, highseas, and antarctica regions
##
## Reading layer `regions_2017_update' from data source `/home/shares/ohi/git-annex/globalprep/spatial/v2017' using driver `ESRI Shapefile'
## Simple feature collection with 526 features and 7 fields
## geometry type: MULTIPOLYGON
## dimension: XY
## bbox: xmin: -18040060 ymin: -9020048 xmax: 18040080 ymax: 9020048
## epsg (SRID): NA
## proj4string: +proj=moll +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defsConvert saltmarsh shapefiles into same CRS as our region zones raster
Fasterize/rasterize: Where there is saltmarsh assign a value of 1 and NA otherwise
Stack rasters and adjust
Calculate zonal stats with zones raster and new combined saltmarsh. Convert to km^2 and save int/output files
Data Check
Justification for using ~0.9 km2 for average seagrass polygon area