Observed Patterns of Global Biodiversity

This chapter summarizes and synthesizes known biodiversity patterns, and analyzes them for congruency over space and time. The discussion is limited to macroecological patterns at continental to global scales (thousands of km). The chapter also focuses on the simplest measure of biodiversity—namely, species richness. The discussions cover marine coastal biodiversity, marine pelagic biodiversity, deep-sea biodiversity, terrestrial biodiversity, changes in biodiversity patterns through time, and robustness of documented biodiversity patterns. Among the findings is that averaging across all known species groups on land and in the sea, tropical peaks in species richness were as common as subtropical peaks, whereas species groups cresting in temperate or polar latitudes were more exceptional. Thus, the oft-cited unimodal pattern of biodiversity appears frequently, particularly on land, but there is also evidence that supports a newly emerging paradigm of asymmetric unimodal or bimodal peaks often in the subtropics, and particularly in the marine realm.