Accounting for uncertainty when mapping species distributions: The need for maps of ignorance

TLDR

Accurate mapping of species distributions, essential for biogeography, is typically achieved through occurrence plots, expert range maps, or model‑based estimations, yet all approaches are inherently uncertain due to data quality, methodological biases, and dynamic species ranges. The authors review the primary sources of uncertainty in species distribution mapping and propose a code of good practices to mitigate them. They conduct a review of uncertainty sources and develop a set of best‑practice guidelines. They argue that uncertainty must always be explicitly considered and recommend creating maps of ignorance to indicate reliable versus uncertain distribution areas.

Abstract

Accurate mapping of species distributions is a fundamental goal of modern biogeography, both for basic and applied purposes. This is commonly done by plotting known species occurrences, expert-drawn range maps or geographical estimations derived from species distribution models. However, all three kinds of maps are implicitly subject to uncertainty, due to the quality and bias of raw distributional data, the process of map building, and the dynamic nature of species distributions themselves. Here we review the main sources of uncertainty suggesting a code of good practices in order to minimize their effects. Specifically, we claim that uncertainty should be always explicitly taken into account and we propose the creation of maps of ignorance to provide information on where the mapped distributions are reliable and where they are uncertain.