In 2022, the U.S. Fish and Wildlife Service withdrew the gopher tortoise (Gopherus polyphemus) as a candidate for federal protection across most of its range, citing a rangewide demographic model that predicted many populations would remain large and self-sustaining. In this note, we identify a serious flaw in that model: rather than modeling immigration as movement between real populations, the model paired each population with an abstract “dummy” metapopulation that could spontaneously generate new immigrants out of nowhere. This created a runaway feedback loop that artificially inflated projected population growth and masked the species’ true vulnerability.
Once corrected, the model’s predictions shift dramatically — from a mild rangewide decline to a rangewide collapse. This finding raises serious questions about the scientific basis for the 2022 listing decision, and we call for a formal re-evaluation of that decision along with more rigorous code review for the complex simulation models increasingly used to support conservation policy.
Citation: Loope, K.J., Akçakaya, H.R., Shoemaker, K.T. 2024. Inflated predictions from a flawed model influenced the decision to deny federal protection for the gopher tortoise. Global Ecology and Conservation 54:e03089. https://doi.org/10.1016/j.gecco.2024.e03089