Forest disturbance history

Code

library(terra)
library(sf)
library(ggplot2)
library(knitr)
library(tidyterra)

We used the Tropical Moist Forest product, developed by the European Commission’s Joint Research Centre. This product, based on Landsat images, classifies forest areas and detects annual changes (including deforestation and forest degradation) from 1990 to 2024 at a resolution of 30 metres.

Code

# download tmf - annual change for luzon between 1990 and 2024
dir_tmf <- "data/tmf"
if (!dir.exists(dir_tmf)) dir.create(dir_tmf)
for (yr in 1990:2024) {
  file <- paste0(
    dir_tmf, "/JRC_TMF_AnnualChange_v1_", yr,
    "_ASI_ID76_N20_E120.tif"
  )
  if (!file.exists(file)) {
    paste0(
      "https://ies-ows.jrc.ec.europa.eu/iforce/tmf_v1/download.py?",
      "type=tile&dataset=AnnualChange_", yr, "&lat=N20&lon=E120"
    ) |>
      download.file(file, mode = "wb")
  }
}

Code

tmf_files <- list.files(dir_tmf, pattern = "UMRBPL", full.names = TRUE)
years <- gregexpr("[0-9]+", tmf_files) |>
  regmatches(x = tmf_files) |>
  lapply(as.numeric) |>
  lapply(function(i) i[i > 1900]) |>
  unlist()
data <- data.frame(
  year = years,
  Undisturbed = -1,
  Degraded = -1,
  Deforested = -1,
  Regrowth = -1,
  Water = -1,
  Other = -1
)
area <- list.files("data/umrbpl/", full.names = TRUE, pattern = "shp$") |>
  read_sf() |>
  st_transform(crs = "EPSG:4326")
tmf <- tmf_files |>
  rast() |>
  crop(area) |>
  mask(area) |>
  lapply(function(r) {
    levels(r) <- names(data)
    r
  }) |>
  rast()
names(tmf) <- years

for (i in seq_len(dim(tmf)[3])) {
  for (c in 1:6) {
    cat_mask <- (tmf[[i]] == c)
    n_pixels <- global(cat_mask, fun = "sum", na.rm = TRUE)$sum
    surface_ha <- n_pixels * 30 * 30 / 10000
    data[i, c + 1] <- surface_ha
  }
}

Maps

Code

tmf_years <- tmf[[which(grepl("2010|2015|2020", names(tmf)))]]
ggplot() +
  geom_spatraster(data = tmf_years) +
  facet_wrap(~lyr) +
  scale_fill_manual(values = c("darkgreen", "orange", "red",
                               "green", "lightblue", "grey")) +
  labs(fill = NULL)

Changes in forest area between 1990 and 2024

Code

ggplot(data, aes(x = year)) +
  geom_line(aes(y = Undisturbed, color = "Undisturbed"), size = 0.9) +
  geom_line(aes(y = Degraded, color = "Degraded"), size = 0.9) +
  geom_line(aes(y = Deforested, color = "Deforested"), size = 0.9) +
  geom_line(aes(y = Regrowth, color = "Regrowth"), size = 0.9) +
  scale_color_manual(name = "", values = c(
    "Undisturbed" = "forestgreen",
    "Degraded" = "orange",
    "Deforested" = "red",
    "Regrowth" = "green"
  )) +
  labs(title = "TMF changes from 1990 to 2024", x = "Year", y = "Surface (Ha)")