One major focus of conservation biology is the spatial configuration of habitat – how it’s fragmented, how it’s connected, and how geographic patterns across the surface of the Earth influence key ecological measures such as biodiversity. Spatial characteristics like area are often used to explain biodiversity patterns, such as why there is greater species richness in the tropics than any other geographic region.
However, there’s another dimension to understanding why species are where they are: climate.
Coelho, M.T.P., Barreto, E., Rangel, T.F., Diniz-Filho, J.A.F., Wüest, R.O., Bach, W., Skeels, A., McFadden, I.R., Roberts, D.W., Pellissier, L. and Zimmermann, N.E. 2023. The geography of climate and the global patterns of species diversity. Nature. DOI: 10.1038/s41586-023-06577-5.
This includes not just climate per se, but also the spatial patterns of climate, which, just like physical habitat, can be thought of as covering the globe and having quantifiable attributes like area and isolation. Incorporating climate is a way to think more fully about what creates global biodiversity patterns and how these patterns might shift under climate change.
Looking beyond geographic space to include climate space in biodiversity models may be a better way to explain patterns we see. Researchers recently did this by classifying climate across the surface of the Earth, much in the same way habitat is classified.
This allowed them to think about the geography of climate, particularly in terms of climate area and climate isolation (i.e. how disconnected different climate types are). They could then determine how well these spatial measures, along with climate in and of itself, explain global biodiversity patterns among terrestrial tetrapods (birds, mammals, amphibians, and reptiles), which include over 30,000 species.
By using the geography of climate and climate itself as predictors, they were able to explain almost 90% of the variation in species richness in climate space across all four groups. The amount of explanation attributed to the geography of climate was almost twice the effect of climate itself.
As for global patterns, climate conditions that covered a larger area and were more isolated tended to harbor higher levels of diversity. However, these larger climate areas didn’t necessarily correlate to greater connectivity – climate area was strongly correlated with the number of climate fragments.
Specific climate regions also showed unique patterns. Tropical climates, while largest in area and concentrated in latitude, were actually more fragmented and isolated than temperate or polar climates. There were also regions that countered the general trends: mountainous climates tended to have greater biodiversity than expected by the climate and climate geography, while desert climates tended to have less biodiversity than expected.
The main message is that it’s important when considering biodiversity to think of not only geographical space, but climate space as well. This allows for a more multi-dimensional view of the factors that determine patterns of overall species richness. This in turn helps to understand how climate change might shift biodiversity patterns in the future, contributing to better decision-making in the present.
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