Comments on the IUCN Red List 2025 Reclassification of the Green Sea Turtle

 The IUCN Red List classification of the Green Sea Turtle, which was listed as Endangered (EN) as recently as 2023, was downgraded to Least Concern (LC) in late 2025 [1]. I welcome the final conclusion of LC, but disagreeing with several methodological points in the assessment process.

1. The Logical Contradiction in Omitting Criterion E

The handling of Criterion E (extinction risk assessment) is logically unfair. The IUCN asserts that a species can be listed under threatened categories if it meets other criteria, even if it fails to meet Criterion E (although I disagree with it [2]). However, by choosing not to run or apply Criterion E simply because the species already failed to meet Criteria A through D, the committee creates a catch-22: Criterion E becomes effectively obsolete.

While it is highly improbable that the global Green Sea Turtle population would trigger Criterion E, individual subpopulations might exhibit different results from Criteria A–D; some may be higher or lower. To maintain scientific integrity across the Red List framework, Criterion E should be evaluated independently of the other metrics.

2. Methodological Underestimation of Population Trends

The assessment report states:

"In the absence of long-term data, we assumed that population abundance three generations ago (~135 years), was similar to the first observed abundance rather than assuming that the population has always been in a decline (or increase)."

This flatline assumption mathematically underestimates the true rate of change. By drawing a static line backward to a historical era (~135 years ago), the model effectively erases the historical context.

A more rigorous approach would be to extrapolate the known trend. Since we have reliable data spanning the 54 years between 1970 and 2024, we should calculate the observed rate of change R for this period and apply it over the full three generations as R^(135/54). In the case of the Green Sea Turtle, because the recent population has been increasing, the final conclusion of "Least Concern" would remain unchanged. 

3. Misdefining the "Shifting Baseline" Problem

The report conflates data gaps with a well-known ecological concept. The committee frames the use of 1970s data (due to the lack of numbers from 2–3 generations ago) as an unavoidable "Shifting Baseline" problem.

This is a misapplication of the term. A true Shifting Baseline Syndrome occurs when a historical population (or the biological carrying capacity) undergoes a catastrophic collapse, stabilizes at a severely depleted level for three generations, and then—because it is no longer declining—gets removed from the threatened list due to human amnesia regarding past abundance. Substituting a known data gap (1970) for an unknown historical value (1900) is a data-mangling compromise, not a true shifting baseline issue.