Most recent cross-country analyses of economic growth have neglected the importance of physical geography. This paper reviews the distinctive development challenges faced by economies situated in tropical climates. Using geographic information system (GIS) mapping, the paper presents evidence that production technology in the tropics has lagged behind temperate zone technology in the two critical areas of agriculture and health, and this in turn opened a substantial income gap between climate zones. The difficulty of mobilizing energy resources in tropical economies is emphasized as another significant contributor to the income gap. These factors have been amplified by geopolitical power imbalances and by the difficulty of applying temperate-zone technological advances in the tropical setting. The income gap has also been amplified because poor public health and weak agricultural technology in the tropics have combined to slow the demographic transition from high fertility and mortality rates to low fertility and mortality rates. The analysis suggests that economic development in tropical ecozones would benefit from a concerted international effort to develop health and agricultural technologies specific to the needs of the tropical economies.