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Compute tree cover forest mask for a specific year

compute_treecover.Rd

This function computes a tree cover forest mask layer for a given year based on a 2000 tree cover baseline - the Hansen Global Forest Change (GFC) dataset or a 2010 tree cover baseline - the GLAD 2010 Tree Canopy Cover dataset.

Usage

compute_treecover(
  year,
  gfc_folder = "data/GFC",
  treecover_threshold = NULL,
  coords = NULL,
  output_folder = "data/treecover_calc",
  num_cores = 1,
  baseline = 2010
)

Arguments

year

Integer. The year for which to compute the tree cover (2001-2023).

gfc_folder

Character. Path to the folder containing GFC dataset files. Default is "data/GFC".

treecover_threshold

Numeric. Optional threshold for tree cover (0-100) at baseline year. If provided, only areas with tree cover values >= this threshold will be considered. Default is NULL (no threshold).

coords

Character. Coordinates of the tile to process, e.g., "10N_020E". If NULL, processes all available tiles.

output_folder

Character. Path to the folder where output rasters should be saved.

num_cores

Integer. Number of cores to use for parallel processing.

baseline

Integer. Baseline year for tree cover dataset. Can be 2010 (default) or 2000.

Value

A list. If coords is specified, only one tile is processed and returns a file path to a single raster. Otherwise, returns a set of file paths, each representing the tree cover at baseline for the specified year for different tiles. The rasters are computed taking the tree cover values from the baseline rasters, removing pixels where forest loss was recorded at or before the provided year. If a tree cover threshold is provided, all tree cover pixels below the threshold are set to NA. Rasters are saved as a GeoTIFF file saved in the output_folder.

Details

This function computes a tree cover forest mask by leveraging a baseline tree cover and forest loss data. It uses two primary types of input files:

  1. Tree cover data, which serves as the baseline:

    • For the 2000 baseline, the function uses files from the Hansen dataset for tree cover.

    • For the 2010 baseline, the function uses GLAD tree cover files.

    • Tree cover values represent the percentage of tree cover (0-100\

  2. Forest loss year data:

    • The function uses Hansen Global Forest Change lossyear files.

    • Values in these files indicate the year of forest loss (1-23, corresponding to years 2001-2023), or 0 if no loss occurred.

The function applies the following steps:

  1. It reads the tree cover and forest loss rasters for the specified year and location.

  2. If a treecover_threshold is provided, all tree cover pixels with values below the threshold are set to NA.

  3. It removes pixels where forest loss was recorded at or before the specified year.

  4. The resulting raster represents a tree cover forest mask for the specified year, with areas of low tree cover or forest loss masked out.

  5. The function saves the resulting raster as a GeoTIFF file in the output_folder.

References

Hansen, M.C., Potapov, P.V., Moore, R., Hancher, M., Turubanova, S.A., Tyukavina, A., Thau, D., Stehman, S.V., Goetz, S.J., Loveland, T.R., Kommareddy, A., Egorov, A., Chini, L., Justice, C.O., and Townshend, J.R.G., 2013, High-Resolution Global Maps of 21st-Century Forest Cover Change: Science, v. 342, no. 6160, p. 850-853, at http://www.sciencemag.org/content/342/6160/850.abstract.

Examples

if (FALSE) { # \dontrun{
# Compute all tiles tree cover for 2015 using 2010 baseline
treecover_2015 <- compute_treecover(2015)

# Compute 30% thresholded tree cover for the 10N, 20E tile for 2005 using
# 2000 tree cover baseline
treecover_2020 <- compute_treecover(2020,
                                    treecover_threshold = 30,
                                    coords = "10N_020E",
                                    output_folder = "data/treecover_calc",
                                    baseline = 2000)
} # }