Chapter 2 examines an ‘agricultural revolution’ in the rural areas around Lake Tanganyika’s emporia, characterised by changes in labour regime, crop choice, and land-use. It uses climatological sources and the wider context of the Indian Ocean monsoon system to examine how the introduction of new crops (cassava, maize, and rice) affected agricultural productivity and vulnerability to the effects erratic climatic conditions, including droughts and floods. It argues that benign environmental conditions in the Indian Ocean World during mid-century contributed to the viability of large port-towns. However, erratic rainfall from 1876 onwards, the replacement of East African staples with less drought-resistant crops, and the increased demands on the region’s agricultural supplies from emporia and the caravan trade exacerbated trends towards violence and instability during the late 1870s and 1880s.