Overall reduction across subpopulations for IUCN criterion A

Combine the reductions of several subpopulations into one reduction for the taxon, following section 4.5.4 of the IUCN Red List guidelines. The overall reduction is the change in the summed population, which equals the average of the subpopulation reductions weighted by their size three generations ago.

Usage

rl_overall_reduction(
  past = NULL,
  present = NULL,
  reduction = NULL,
  subpopulation = NULL,
  subcriterion = c("A2", "A1", "A3", "A4")
)

Arguments

past: Numeric vector of subpopulation sizes at the start of the window (three generations ago).
present: Numeric vector of subpopulation sizes at the end of the window.
reduction: Numeric vector of subpopulation reductions (proportions).
subpopulation: Optional labels for the subpopulations.
subcriterion: Which criterion A subcriterion sets the thresholds for category_a: "A2" (default), "A1", "A3" or "A4".

Value

A one row tibble with the overall reduction and reduction_pct, the number of subpopulations, the summed past and present sizes, and category_a. The per-subpopulation table is attached as the "subpopulations" attribute.

Details

Give any two of past, present and reduction for each subpopulation and the third is worked out from reduction = 1 - present / past. The sizes should already be projected to the start and end of the same window, for example with rl_reduction().

References

IUCN Standards and Petitions Committee. 2024. Guidelines for Using the IUCN Red List Categories and Criteria. Version 16, section 4.5.4.

Examples

# Guidelines Example 1: past and present sizes for three subpopulations
rl_overall_reduction(
  past = c(10000, 8000, 12000),
  present = c(5000, 9000, 2000),
  subpopulation = c("Pacific", "Atlantic", "Indian")
)
#> # A tibble: 1 × 6
#>   reduction reduction_pct n_subpop past_total present_total category_a
#>       <dbl>         <dbl>    <int>      <dbl>         <dbl> <chr>     
#> 1     0.467          46.7        3      30000         16000 VU