A simple recent-vs-historical record-velocity indicator computed per species from its OBIS year histogram. Implemented in src/lib/silence-score.ts.
`` trend = (records in last 5 years) / (5-year rolling average across full history) ``
| Label | Meaning |
|---|
| Declining | trend < 0.4 — recent records well below historical average |
| Stable | 0.4 ≤ trend < 1.5 |
| Resurgent | trend ≥ 1.5 — large bump in recent observations |
| Sparse | <6 years of usable data — no verdict |
Caveats
- This is a signal, not a verdict. It does not correct for sampling effort.
- Recent dips can reflect reporting lag (datasets published 1–3 years late),
not actual species decline.
- The label is most reliable for species with long, dense observation
histories (e.g. Blue whale (Balaenoptera musculus) from cetacean surveys).
Future direction
A future version may incorporate OBIS — Ocean Biodiversity Information System sampling-effort denominators and overlay Ship strikes / fishing-pressure covariates to distinguish "fewer records" from "actually quieter ocean."