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Lower/upper Area of Occupancy bounds and the Criterion B2 category range

Source: R/aoo_bounds.R
aoo_bounds.Rd

Turns the occurrence-based AOO (the lower bound) and the Area of Habitat (AOH; the suitable/natural habitat within the range, an upper bound) into a bracketed AOO and the corresponding range of Criterion B2 size categories, following the IUCN guidance that the true AOO lies between an occurrence-based minimum and a habitat-based maximum (Brooks et al. 2019; IUCN Standards and Petitions Committee 2024), as implemented in sRedList (Cazalis et al. 2024).

Usage

aoo_bounds(aoo_lower_km2, aoh_km2 = NA_real_, eoo_km2 = NA_real_)

Arguments

aoo_lower_km2

The occurrence-based AOO in km^2 (from calc_aoo); the lower bound.

aoh_km2

The Area of Habitat (suitable/natural habitat area) within the range, in km^2 - e.g. the natural_km2 of the EOO conversion from summarise_conversion. NA (default) if unknown.

eoo_km2

The EOO in km^2 (from calc_eoo), used to cap the upper bound. NA (default) leaves the upper bound uncapped.

Value

A list with aoo_lower, aoo_upper, aoh (the clamped habitat area used), cat_lower / cat_upper (the B2 size category at each bound, e.g. "EN (B2 size)") and cat_range (a compact string such as "EN-VU", or a single category when both bounds agree).

Details

The upper bound is the AOH clamped so it is never below the lower bound and never above the EOO (occupancy cannot exceed the extent of occurrence). When the AOH is not available (aoh_km2 = NA, e.g. land cover was not computed) the upper bound falls back to the lower bound and the range collapses to a single category.

References

Brooks T.M. et al. (2019) Measuring terrestrial Area of Habitat (AOH) and its utility for the IUCN Red List. Trends in Ecology & Evolution 34:977-986. doi:10.1016/j.tree.2019.06.009

Cazalis V. et al. (2024) Accelerating and standardising IUCN Red List assessments with sRedList. Biological Conservation 298:110761. doi:10.1016/j.biocon.2024.110761

See also

calc_aoo, iucn_category_B, iucn_category_B_range

Examples

# Occurrence AOO of 48 km^2, but 900 km^2 of natural habitat within a
# 6000 km^2 EOO: AOO is bracketed EN (lower) to VU (upper).
aoo_bounds(aoo_lower_km2 = 48, aoh_km2 = 900, eoo_km2 = 6000)
#> $aoo_lower
#> [1] 48
#> 
#> $aoo_upper
#> [1] 900
#> 
#> $aoh
#> [1] 900
#> 
#> $cat_lower
#> [1] "EN (B2 size)"
#> 
#> $cat_upper
#> [1] "VU (B2 size)"
#> 
#> $cat_range
#> [1] "EN-VU"
#>