Mapping Agricultural Change in Eastern Africa: A Geographic Information Systems (GIS) Approach to Early Imperial Sources, 1857–76

Key findings from this study

This research indicates that:

• GIS mapping of explorer accounts reveals spatial and temporal patterns in nineteenth-century crop adoption across inland equatorial eastern Africa between 1857 and 1876.
• Maize, rice, and cassava were incorporated into agricultural systems along caravan routes at different rates in different locales, contributing to intensified food production near commercial centers.
• Divergences between crop mentions in accounts from successive decades indicate changing agricultural practice at specific sites during the twenty-year period.
• The visualizations contextualize documented famine events by showing crop distributions during years of below-average rainfall, revealing vulnerability patterns.

Overview

This study applies GIS mapping to nineteenth-century European explorer accounts to visualize agricultural change in equatorial eastern Africa between 1857 and 1876. The research focuses on the spatial and temporal distribution of crop mentions in primary sources, particularly tracking the introduction and adoption of maize, rice, and cassava alongside indigenous grains and plantains. The analysis covers regions along central caravan routes in present-day Tanzania, Uganda, Burundi, and the Democratic Republic of the Congo. These crops arrived through trade networks linking coastal regions to the interior, contributing to broader transformations in food production systems. The study addresses methodological challenges in documenting agricultural history where archaeological, palynological, and linguistic evidence remains limited. By georeferencing crop references from explorer diaries, letters, and publications onto contemporary maps, the research creates visualizations that reveal localized patterns of crop adoption. The approach enables comparison across different explorers' accounts from successive decades, potentially indicating temporal shifts in agricultural practice. The work contextualizes agricultural change within documented climate variability, famine events, and the expansion of commercial centers during this period.

Methods and approach

The research identifies all crop references in accounts by explorers including Richard Burton, John Hanning Speke, James Augustus Grant, David Livingstone, Henry Morton Stanley, and Verney Lovett Cameron traveling through the region between 1856 and 1876. The study extracts mentions of maize, rice, cassava, sorghum, millet, plantains, and bananas from explorer diaries, letters, and publications. These primary sources represent the principal documentary evidence for inland equatorial eastern Africa during this period. The analysis uses contemporary maps created based on explorer descriptions as cartographic foundations for visualization. Crop references are georeferenced onto these maps to show spatial distribution patterns. Temporal differences emerge by comparing visualizations from explorers who traveled through the same locales in different decades. The GIS approach enables systematic investigation of documentary sources for evidence of agricultural change at localized scales. The study focuses on regions west of the East Arc mountains along caravan routes facilitating long-distance ivory trade. The methodology addresses limitations of oral traditions, which cannot be precisely dated, and the absence of sufficient archaeological or palynological research for most inland areas.

Results

The GIS visualization approach successfully mapped crop distributions across specific regions including Ugogo, Unyamwezi, areas surrounding Lake Victoria, regions near Lake Tanganyika, and Manyema. The digital mapping revealed spatial patterns in the presence and availability of different crops as documented in explorer accounts across two decades. Divergences between descriptions from explorers traveling through the same locales in the 1850s versus the 1860s and 1870s indicated temporal changes in crop choice at specific sites. The visualizations demonstrated that maize, rice, and cassava were incorporated into agricultural systems alongside indigenous sorghum and millet as well as longer-established plantains. The mapping contextualized crop distributions relative to documented commercial and political centers, showing relationships between agricultural patterns and trade networks. The study identified correlations between crop availability patterns and documented famine events occurring during years and seasons with below-average rainfall. The georeferenced data revealed localized variations in agricultural practice that had not been systematically documented at this scale previously.

The research established a foundation for archaeological and palynological investigation by identifying specific locales where agricultural change likely occurred during the nineteenth century. The visualizations showed that the introduction of New World crops and Asian rice contributed to intensified food production near caravan routes and administrative centers. The mapping demonstrated that agricultural transformation was geographically uneven, with some areas showing evidence of new crop adoption earlier than others. The study confirmed that documentary sources, despite their problematic origins in European imperial ventures, contain systematic geographic and agricultural information that can be extracted through GIS methods. The temporal comparisons revealed that crop choice was dynamic rather than static during this twenty-year period, supporting the characterization of these changes as part of an agricultural revolution in parts of equatorial eastern Africa.

Implications

The research provides a methodological framework for extracting agricultural information from problematic historical sources through systematic spatial analysis. The GIS approach enables future researchers to identify specific locations where archaeological excavation or palynological sampling could verify nineteenth-century agricultural change documented in written accounts. The visualizations offer evidence for understanding how the introduction of maize, rice, and cassava altered labor requirements, land-use patterns, and vulnerability to climate variability in different locales. The study demonstrates that agricultural transformation in inland eastern Africa was connected to expanding trade networks and commercial development rather than occurring uniformly across the region. The mapping contextualizes subsequent environmental challenges documented in early colonial sources by showing pre-existing patterns of crop diversity and food production. Understanding nineteenth-century agricultural change has implications for interpreting later famine events and colonial-era agricultural policies.

The research illuminates how global crop movements reshaped food systems in African interior regions during a period of increasing connection to international commerce. The spatial analysis reveals that coastal and hinterland regions experienced agricultural change within different temporal and climatic contexts than inland areas, suggesting regionally specific trajectories of transformation. The study's documentation of crop distributions during years of documented below-average rainfall provides evidence for assessing agricultural vulnerability to climate variability before colonial intervention. The work demonstrates that systematic investigation of explorer accounts can yield localized agricultural data previously considered inaccessible. The GIS visualizations enable comparison with later colonial and post-colonial agricultural patterns, potentially revealing continuities or disruptions in crop choice over longer timeframes. The research establishes that digital methods can extract quantifiable spatial information from narrative historical sources, opening possibilities for similar approaches to other aspects of nineteenth-century African history.

Scope and limitations

This summary is based on the study abstract and available metadata. It does not include a full analysis of the complete paper, supplementary materials, or underlying datasets unless explicitly stated. Findings should be interpreted in the context of the original publication.