How do biogeographers divide Earth into regions based on plant and animal distributions?

Biogeographers divide Earth into regions—often termed floral kingdoms or faunal realms—by analyzing the geographic distribution of organisms and the factors influencing those patterns. These classifications are not rigid but are used as tools to understand evolutionary history, ecological constraints, and dispersal mechanisms.123

Methods of Classification

• Historical and Environmental Factors: Divisions are based on a combination of current climatic conditions, geologic history (such as continental drift), and the evolutionary history of specific taxa.41
• Geographic Barriers: Regions are typically separated by natural boundaries like oceans, mountain ranges, or deserts that restrict the movement of species. For example, the Wallace Line serves as a famous, though debated, boundary between distinct faunal groups.56
• Biomes: Scientists also categorize the biosphere into biomes, which are ecological communities sharing similar climates and geologic features that support species with analogous life strategies.4

Key Distinctions

While plant and animal distributions often overlap, discrepancies exist due to differences in mobility and evolutionary age. For instance, plants are generally less mobile than animals, meaning phytogeographic regions often reflect more ancient phases of Earth's history. Consequently, biogeographers may recognize different boundaries for flora and fauna to better account for these unique biological histories.35