D. Whittlesey's classification of agricultural regions, proposed in 1936, remains one of the most comprehensive and widely accepted frameworks for understanding global agricultural patterns. An American geographer, Whittlesey recognized the need for a systematic approach to categorize the diverse agricultural practices across the world. His classification was not merely based on dominant crops or livestock but incorporated a holistic view of agricultural systems, considering both physical and human factors.

Whittlesey's classification was built upon five primary criteria:

1. Crop and Livestock Association: This criterion focused on the dominant types of crops grown and animals raised in a particular region. It considered whether agriculture was primarily arable (crop-based), pastoral (livestock-based), or a combination of both, and the specific species involved. For example, rice-dominant intensive subsistence farming versus wheat-dominant commercial grain farming.

2. Methods Used to Produce and Market Products: This criterion examined the techniques and technologies employed in farming, as well as how agricultural produce reached consumers. It differentiated between primitive methods (e.g., shifting cultivation) and modern, mechanized techniques (e.g., commercial agriculture). It also considered whether products were for local consumption (subsistence) or for sale in distant markets (commercial).

3. Intensity of Application of Capital and Labor: This criterion assessed the amount of investment in terms of money, machinery, fertilizers, and human effort per unit of land. It distinguished between intensive agriculture, which uses high inputs of capital and labor to maximize yield from a small area, and extensive agriculture, which uses lower inputs over larger areas.

4. The Disposal of Products: This criterion looked at the ultimate destination and use of agricultural output. It differentiated between products consumed directly by the farmer and their family (subsistence), those sold for profit (commercial), or those used as raw materials for industries.

5. The Ensemble of Structures Associated with Agricultural Production: This broad criterion encompassed the socio-economic and cultural aspects of farming. It included factors such as farm size, land tenure systems (e.g., communal, individual ownership, tenancy), settlement patterns (e.g., dispersed, nucleated), and the overall cultural landscape shaped by agricultural activities.

Based on these five criteria, Whittlesey identified 13 major agricultural regions across the globe, such as Nomadic Herding, Shifting Cultivation, Intensive Subsistence (with and without rice dominance), Commercial Grain Farming, Livestock Ranching, Mediterranean Agriculture, and Plantation Agriculture, among others. While the classification provided a robust framework, its static nature means it doesn't fully capture the rapid changes and globalization impacting agricultural systems today. Nevertheless, it remains a foundational concept in agricultural geography, offering a systematic way to understand the spatial distribution and characteristics of farming worldwide.