Towards a standardization and unification of global terrestrial biome classifications

Global terrestrial biome classifications function as basic units in large-scale biogeographic and ecological research. Although there is an implicit agreement about general global patterns, there is a great variety of such concepts with significant deviations in numbers of categorial classes and their spatial extent. These differences result from variant methodological approaches (e.g., expert-based, remote sensing, modelling) and distinct underlying criteria. Although frequently used as a reference, the decision for a specific biome classification is often uninformed or based on the assumption of general consensus. However, the spectrum of biome classifications ranging from expert-based delineations only available as paper prints to high-resolution global maps derived from Earth observation exhibit great variability. Class numbers differ immensely between different concepts and spatial agreement is low. Here, we aim at providing a standardized catalogue of global terrestrial biome and land-cover classifications. Comparison between concepts reveals the degree of spatial congruency and overall similarity to ease informed selection and to avoid discrepancies with more consistent approaches. We propose an optimized product that is condensed from the characteristics of commonly used classifications. 31 published biome classifications were standardized to equal resolution and projection. Hierarchical clustering was used to provide a congruent biome map and to produce a disagreement map of the reviewed concepts. The standardized final biome catalogue enables easy application of individual classifications by setting up a context of common standards. We encourage refined considerations in the selection of global terrestrial biome classifications in biogeographic and ecological research. Therefore, we present a standardized inventory, the biome catalogue, and a novel map combining the expertise of present concepts.

An optimized global biome map based on various concepts.