er_score across v7’s valid species.
| er_score | Species | Share |
|---|---|---|
| 100 | 44 | 0.3% |
| 50 | 54 | 0.3% |
| 25 | 104 | 0.6% |
| 20 | 44 | 0.3% |
| 10 | 121 | 0.7% |
| 5 | 105 | 0.7% |
| 2 | 102 | 0.6% |
| 1 | 15,579 | 96.4% |
7 Extinction Risk
Extinction-risk scoring turns a species’ conservation status into a numeric weight, so that a cell holding rare or threatened species scores higher than one holding common ones. The MST combines three US federal frameworks with the international IUCN Red List into a single score from 1 to 100.
7.1 Regulatory framework
7.1.1 Endangered Species Act (ESA)
The Endangered Species Act (1973) protects species listed as Endangered (EN) or Threatened (TN) by NMFS (marine species) or FWS (terrestrial and coastal species). ESA listing is the strongest signal available and drives the score for US-listed species.
7.1.2 Marine Mammal Protection Act (MMPA) — assigned by taxonomy
The Marine Mammal Protection Act (1972) protects all marine mammals in US waters regardless of ESA status, so the MST assigns it by taxonomy: every taxon in WoRMS class Mammalia, matched on AphiaID.
This is deliberate. Deriving the flag from the NMFS Species Directory instead — as earlier releases did — captures only the managed stocks listed there, roughly 70 against the ~137 marine-mammal taxa the analysis actually carries, and it silently omitted the FWS-managed species entirely (walrus, polar bear, sea otter, manatee, dugong). Taxonomy is the complete test because the statute is written in taxonomic terms.
The floor is 20, higher than the MBTA’s, because the MMPA imposes a stronger statutory standard: it affirmatively requires marine mammal populations to be maintained at Optimum Sustainable Population levels and mandates recovery, whereas the MBTA is primarily a prohibitive take statute. Marine mammals also tend to have lower reproductive rates and longer recovery times than most seabirds.
7.1.3 Migratory Bird Treaty Act (MBTA) — an explicit species list, not all birds
The Migratory Bird Treaty Act (1918) protects migratory birds native to the United States and its territories — which is an explicit list, not a taxonomic class.
ImportantThe MBTA floor is the FWS CFR 50 §10.13 list, not all Aves
A bird absent from 10.13 — a non-US or non-migratory species — receives no MBTA floor. Treating “bird” as equivalent to “MBTA-protected” would apply a US statutory floor to species the statute does not cover, inflating their weight in US waters.
Note also that most 10.13 birds are terrestrial. The list sets the value of the birds that reach scoring; what keeps terrestrial birds out of the score in the first place is the marine-relevance cull (see Section 6.4).
7.1.4 IUCN Red List
For species with no US federal listing, the score falls back to the IUCN Red List category: Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), Least Concern (LC) and Data Deficient (DD).
Note
TN is an ESA status (Threatened), not an IUCN one — IUCN uses NT for Near Threatened. msens::compute_er_score() errors on a code such as IUCN:TN rather than scoring it through a default, because a silently-defaulted code is a wrong weight that nothing surfaces.
7.2 Scoring
Scores are computed by msens::compute_er_score(), on two tracks.
7.2.1 US-listed species
For a species with an ESA listing, or MMPA or MBTA protection, the score is the maximum of the applicable components:
\[ \text{er\_score} = \max(\text{ESA base},\; \text{MMPA floor},\; \text{MBTA floor}) \tag{7.1}\]
| Component | Score |
|---|---|
| ESA Endangered (EN) | 100 |
| ESA Threatened (TN) | 50 |
| ESA not listed (LC) | 1 |
| MMPA protected (all Mammalia) | 20 |
| MBTA protected (CFR 50 §10.13) | 10 |
Worked examples:
- ESA Endangered whale (also MMPA): \(\max(100, 20) = \mathbf{100}\)
- ESA Threatened seabird on the 10.13 list: \(\max(50, 10) = \mathbf{50}\)
- Marine mammal with no ESA listing: \(\max(1, 20) = \mathbf{20}\)
- 10.13 migratory bird with no ESA listing: \(\max(1, 10) = \mathbf{10}\)
A species carrying an MMPA or MBTA floor is routed onto this track even when it has no ESA listing, which is what guarantees the floor is actually applied rather than being lost to the IUCN track.
7.2.2 Species with no US listing
| IUCN category | Score |
|---|---|
| Critically Endangered (CR) | 50 |
| Endangered (EN) | 25 |
| Vulnerable (VU) | 5 |
| Near Threatened (NT) | 2 |
| Least Concern / Data Deficient / other | 1 |
The IUCN scale is deliberately lower than the ESA one: a US statutory listing is a stronger, jurisdiction-specific statement about a species in US waters than an international assessment.
Species with no matching code at all receive the baseline of 1.
7.2.3 The governing score, and where it is applied
A taxon may carry several conservation codes at once — one per contributing dataset — and they can disagree, or be stale. The pipeline therefore computes one governing score per taxon: the most protective across its datasets, with a US national listing overriding the IUCN category, plus the statutory floors.
That governing score is applied at merge time, to the range cells — the point at which a species’ presence in a cell should carry its governing risk rather than whatever code the source dataset happened to record. Scoring then reads values that already reflect it.
Of v7’s 16,153 valid species, 62 carry the MMPA floor and 132 the MBTA floor.
7.3 Scale
Scores run from 1 to 100 and represent a percentage-like weight — 100 being maximum risk and 1 the baseline. Integers are used for storage efficiency; conceptually the scale is a 0–1 weight multiplied by 100.
7.4 Implementation
msens::compute_er_score(
extrisk_code, # "NMFS:EN", "FWS:TN", "IUCN:CR", ...
is_mmpa = FALSE, # MMPA protection (all WoRMS Mammalia)
is_mbta = FALSE) # MBTA protection (FWS CFR 50 §10.13)extrisk_code is AUTHORITY:STATUS, where the authority is NMFS, FWS or IUCN, and the status is an ESA code (EN, TN, LC) or an IUCN code (CR, EN, VU, NT, LC, DD). Any other combination is an error, not a default.