World bioclimatic zonation

Abstract

Attempts to regionalize world climates began in the early 1800s, based partly on natural landscapes. The first attempts were empirical, but better understanding of global atmospheric circulation led eventually to ‘genetic’ approaches, based on the mechanisms that generate different climate types. It was recognized early that climatic zones follow mainly from temperature, at least in lowlands, but the duration of wet and dry seasons also characterizes many climate types quite distinctly. This paper expands the familiar genetic climate classification of Walter to provide a simple, globally consistent, more complete classification that also recognizes subtypes and transitions explicitly, and facilitates understanding of world soil and vegetation types. This genetic approach is preferable to empirical systems, such as Köppen, because it: has fewer main typesrecognizes types tied more directly to dynamic mechanisms that cause different climate typeshas a more general and flexible set of subtype descriptorsunifies some climatic concepts bettermatches natural vegetation and landscapes better, andis more flexible under changing global climatic conditions than are empirical limits. Zonal climate types are easier to understand and to teach, since they are tied directly to atmospheric dynamics and reflect visible geographic regions and landscapes. The resulting global geographic framework also provides a basis for testing the validity of putatively general ecological models.