Droughts, conflict, and the African slave trade

Abstract

Historians have frequently suggested that droughts helped facilitate the African slave trade. By introducing a previously unused dataset on 19th century rainfall levels in Africa, I provide the first empirical answer to this hypothesis. I show that negative rainfall shocks and long-run shifts in the mean level of rainfall increased the number of slaves exported from a given region and may have had a persistent impact on the level of development today. Using geocoded data on 19th century African conflicts, I show that these drought conditions also increased the likelihood of conflict, but only in the slave exporting regions of Africa. I also explore the role of household desperation, the internal African slave market, and disease outbreaks in explaining the negative relationship between droughts and slave exports. I find limited evidence for for these alternative mechanisms, with household desperation having the most empirical support. These results contribute to our understanding of the process of selection into the African slave trade.

Maize and Precolonial Africa

“…In recent work, Fenske and Kala (2017) show that the suppression of the West African slave trades in 1807 increased conflict elsewhere on the African continent. Our paper is more closely related to that of Boxell (2018) who shows that droughts increased slave exports by increasing conflict. To help explain his empirical results, Boxell builds a model based on Fenske and Kala (2015) to highlight how drought induced decreases in agricultural productivity can increase slave exports by affecting the opportunity cost of participating in the slave trades.…”

“…This means that our estimates could be capturing the effects of other time-varying aspects of European contact, such as the sale of firearms, that may have affected both population density and slave exports. Similarly, recent research by Fenske and Kala (2015) and Boxell (2018) show that increased temperatures and rainfall are associated with reductions in slave exports, respectively. This means that our estimates could also be capturing the effects of weather and seasons.…”

“…The second specification, reported in column (2), adds the natural log of average distance to an ice-free coast, the natural log of one plus the fraction of land that is within 100 km of an ice-free coast and region indicators for north, west, east, south and central Africa, all interacted with time fixed effects to account for differential trends in European contact. In our preferred specification, reported in column (3), we add the natural logs of two key determinants of climate, distance to the equator and elevation, interacted with time fixed effects to account for the possibility 32 It is important to note that the results reported by Fenske and Kala (2015) and Boxell (2018) suggests that our estimates would be downward biased, at least for slave exports. For example, Boxell (2018) finds that increased rainfall is associated with reductions in slave exports.…”

“…In our preferred specification, reported in column (3), we add the natural logs of two key determinants of climate, distance to the equator and elevation, interacted with time fixed effects to account for the possibility 32 It is important to note that the results reported by Fenske and Kala (2015) and Boxell (2018) suggests that our estimates would be downward biased, at least for slave exports. For example, Boxell (2018) finds that increased rainfall is associated with reductions in slave exports. Given that maize requires a minimal level of moisture to grow (Miracle, 1966;McCann, 2005), a rainier climate would increase the likelihood of adoption.…”

“…Dalton and Leung (2015); Eltis et al (2010)). However, some recent research has begun to examine the supply side determinants of the slave trades, such as the ruggedness of terrain (Nunn and Puga, 2012), climate shocks (Fenske and Kala, 2015;Boxell, 2018), the managerial quality of ship captains (Dalton and Leung, 2016), and the guns-for-slave cycle (Whatley, 2018). We contribute to this literature by demonstrating how the agricultural productivity shock created by the introduction of maize increased the supply of slaves from Africa during the slave trades.…”