Assessing biases and broader applicability of expert range maps

Study of more than 50,000 animals shows bias of expert range maps at administrative borders and failure to capture all known occurrences

GBIF-mediated data resources used : 638,809,455 species occurrences
Amphispiza bilineata
Amphispiza bilineata (Cassin, 1850) observed in Mexico by Enrique Perez Carrillo (CC BY-NC 4.0)

Having accurate maps of species distributions is fundamental to assessing conservation priorities and developing targeted conservation strategies, but also to understanding basic biodiversity patterns.

This study analyses expert range maps of 50,000 animal species to test the assumption that these provide consistent and standardized estimates of species' ranges.

By rasterizing and stacking species range boundaries, the authors created boundary density maps grouped by higher level taxa (mammals, dragonflies and damselflies, amphibians, birds and reptiles) and overlaid these with different features such as administrative boundaries.

This exercise demonstrated an average of 20—30 per cent of non-coastal species range boundaries coinciding with country borders, many with no clear geophysical boundaries. When considering species richness, 60 per cent of areas with the highest spatial turnover in species occurred at political boundaries.

Finally, the authors compared the expert maps with GBIF mediated data, finding 80 per cent of taxa having more than 30 per cent of their occurrences outside the corresponding range map.

Taken together, these results reveal high bias of expert range maps at administrative borders, suggesting a need for alternative approaches to reconstructing patterns of distribution.

Hughes AC, Orr MC, Yang Q and Qiao H (2021) Effectively and accurately mapping global biodiversity patterns for different regions and taxa. Global Ecology and Biogeography. Wiley 30(7): 1375–1388. Available at:

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  • China
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