The development of the ancient irrigation system at Engaruka, northern Tanzania: physical and societal factors

Abstract

Climate data from Empakaai Crater in northern Tanzania, covering the last 1200 years, are related to the establishment, development and decline of the ancient irrigation system at Engaruka. New dates for the system are linked to reconstructed climatic variations and historical data on long‐distance and regional trade and migration patterns. A shift from a comparatively humid climate to drier conditions in the 1400s prompted the establishment of irrigated agriculture at Engaruka, and a flourishing long‐distance trade increased its value as a water and food source for passing caravans. Once established, the land‐use system at Engaruka was sufficiently resilient to survive and even intensify during much drier climate from c. 1500 to 1670 CE (Common Era) and during the decline of caravan trade between c. 1550 and 1750. The ancient land‐use system probably reached its maximum extension during the humid conditions between 1670 and 1740, and was deserted in the early to mid 1800s, presumably as a result of the added effects of climate deterioration, the Maasai expansion, and change of livelihood strategies as agriculturalists became pastoralists. Towards the end of the 1800s irrigated agriculture was again established at Engaruka, in part driven by the transfer from pastoral to agricultural livelihoods caused by the Rinderpest.

Geoarchaeological evidence for the construction, irrigation, cultivation, and resilience of 15th--18th century AD terraced landscape at Engaruka, Tanzania

“…This lends support to the assertion by Westerberg et al (2010) that much of the irrigation infrastructure at Engaruka was built during a period of wetter than modern conditions after ca. AD 1670.…”

“…1) that each produce a specific mineral signature (Mattsson et al, 2013). Soils in the area have been classified as Eutric Leptosols (Jones et al, 2013), but Westerberg et al (2010) also note areas of well-developed Andisols along the line of the Engaruka River. The Andisols primarily comprise 2:1 smectite swelling clays.…”

“…Westerberg et al (2010), for example, combined radiocarbon dates from previous excavations within the abandoned settlements at Engaruka with a dated pollen core from Lake Emakat located 15 km to the northwest (as indicated in their fig. 4).…”

“…This research concluded that the former agricultural system should be seen as resilient, arguing that the use of irrigation allowed farming throughout a comparatively dry period between ca. AD 1500 and 1670 (for pollen data, see Ryner et al, 2008; for resilience, see Westerberg et al, 2010). However, this apparent correlation of archaeological and palaeoenvironmental data is merely suggestive of systemic sustainability and resilience because it is unclear how the inhabitants of Engaruka responded to these apparent changes in the rainfall regime.…”

Climate and causation in the Swedish Iron Age: learning from the present to understand the past

“…When times of climate change coincide with times of socioeconomic and political instability, it can lead to societal catastrophes, but also to new developments; • Climatic conditions that are favourable have been an important factor in the past in the rise of new centers for the accumulation of power; • Adaptational strategies, as traced from history, seem to be -flexibility in short-and long-term mobility and in the reorganization of centres; -flexibility in changes in agricultural practices and in types of staple crops -possibility of controlling external trade (Holmgren & Öberg, 2006: 193) The understanding of such a dialectical interplay between climate, on the one hand, and social, political, and economic factors, on the other, has been further developed in the same research group by an interdisciplinary team representing physical geography, human geography, archaeology, and anthropology led by physical geographer Lars-Ove Westerberg (Westerberg et al, 2010). This team traced the establishment, development, and subsequent decline of the ancient irrigation system at Engaruka in Tanzania from the 1400s to early 1800s.…”