Land use in Iron Age Africa

Quantifying the economic and environmental transformation of Africa during the Iron Age (ACACIA)

ACACIA is a interdisciplinary project tackling the problem of the co-evolution of society and environment in Iron Age sub-Saharan Africa. We study the importance of environmental changes, both exogenous, e.g., climate change, and endogenous, e.g., human-induced soil erosion, on the potential for human modification of the landscape.

Land use in Iron Age Africa

In sub-Saharan Africa, the period from approximately 1000 BC to AD 1500 is characterized by the episodic spread of the Iron Age, which in the African context defines the widespread adoption of agriculture, pastoralism, and ferrous metallurgy, the migration and displacement of human populations and the expansion of territory occupied by certain language groups, particularly Bantu. The spread of the Iron Age in sub-Saharan Africa marks an important transition in land cover that had implications both for contemporary climate and for the establishment of landscapes that continue to be valued today as economic, cultural, and ecological resources.This study draws on evidence from interdisciplinary published sources at site, landscape and regional scales to reconstruct subsistence patterns in prehistoric societies. These include: archaeobotanical studies of botanical remains from flotation, grain impressions, starch residue, and phytoliths; palaeoecological studies of the past land cover based on pollen; archaeological evidence such as faunal remains, grindstones, pottery, farming implements, and agricultural architecture; and anthropological and historical studies of ethnographic records, linguistics, and travelers’ written accounts. The model will ultimately allow us to map land use and land cover change in pre-colonial sub-Saharan Africa, and test hypotheses about the relative importance of climate change versus human agency in the development of contemporary African landscapes and ecosystems. We further aim to better understand the long-term environmental effects of past human societies on landscape and climate at regional and continental scales.

Modeling land cover change

In order to gain an appreciation of the importance of the land cover changes associated with subsistence and land use in Iron Age Africa for climate and ecosystems, and to provide a baseline for understanding modern and future human–environment interactions, it is essential to have a large-scale picture of the timing and spatial pattern of land cover change. This project seeks to employ quantitative modeling of anthropogenic land cover change to allow for hypothesis testing on climate feedbacks, and societal vulnerability and resilience to environmental change. The land cover change scenarios used in previous studies have been largely limited to a single variable that represents an estimate of deforestation. However, it is well known that human activities cause a variety of land cover changes relevant to climate and ecosystems going far beyond deforestation. The area that is used for human habitation and the procurement of food and fuel varies based on the population, subsistence strategy, and technology available to a society. Furthermore, the intensity of that land use has varying effects on the landscape with respect to indigenous flora and fauna, biogeochemical cycling, and physical properties of the landscape.

International collaboration

As the ACACIA project is highly interdisciplinary, it would be extremely rare to find a single researcher or even small group of scientists that have the necessary expertise on all aspects of the project. We have therefore been reaching out and profiting from community involvement in the project through international workshops.

In June 2014, we held the first ACACIA workshop at University College London, UK. At this workshop, we presented a prototype version of a land use classification scheme we were developing for Iron Age sub-Saharan Africa. The workshop was supported by the Swiss National Science Foundation through the grant ACACIA (Jed O. Kaplan, Basil Davis, and Carsten Lemmen PIs) and the UCL Institute of Archaeology’s ComPAg project The workshop also supported the activities of at least three current European Research Council Projects: COEVOLVE (PI Jed O. Kaplan), ComPAg (PI Dorian Fuller) and SEALINKS (PI Nicole Boivin). The workshop was attended by about 20 international experts on African archaeology and paleoecology. We made great progress on the improvement of our classification scheme at this workshop, and the outcome led directly to our publication of a substantial review paper (Kay & Kaplan, 2015). In part because of our very positive experience learning from our colleagues at an international setting, we have decided to organize a second ACACIA workshop for the next stage of the project.