Agricultural landscapes are human-manipulated landscapes, most obviously in areas modified by terracing and/or irrigation. Examples from temperate, arid, and desert environments worldwide have attracted the attention of many disciplines, from archaeologists, palaeoecologists, and geomorphologists researching landscape histories to economists, agronomists, ecologists, and development planners studying sustainable resource management. This article combines these interdisciplinary interests by exploring the role archaeology can play in assessing sustainability. Our case study is Engaruka, Tanzania, archaeologically famous as the largest abandoned irrigated and terraced landscape in East Africa. The site has been cited as an example of economic and/or ecological collapse, and it has long been assumed to have been irrigated out of necessity because agriculture was presumed to be nearly impossible without irrigation in what is now a semiarid environment. Geoarchaeological research refutes this assumption, however, demonstrating that parts of the site flooded with sufficient regularity to allow the construction of more than 1000 ha of alluvial sediment traps, in places greater than 2 m deep. Soil micromorphology and geochemistry also record changes in irrigation, with some fields inundated to create paddylike soils. Geoarchaeological techniques can be applied to both extant and abandoned agricultural systems, thereby contributing to an understanding of their history, function, and sustainability.

Flux data from moored sediment trap experiments and mass accumulation rates in sediments were obtained for three sites in the Ross Sea which are currently studied for the formation and transit of High Salinity Shelf Water and Ice Shelf Water. These two data sets were compared to obtain inferences on the coupling between water column processes and sedimentary records. The depth distribution of physical features and concentrations of organic carbon and biogenic silica in box cores and gravity cores were studied. Mass accumulation rates, established on the basis of two conventional 14C dates for each core, range between 7.64 and 19.46 g m−2 yr−1. Although these are productive areas, downward fluxes measured by sediment traps are low: 7.5–25.6, 2.4–17.9 and 0.5–0.9 g m−2 yr−1 for particles, biogenic silica and organic carbon, respectively. The concentrations of biogenic components in surficial sediments are correspondingly low. Simple mass balances were calculated assuming the conservative behaviour of the lithic fraction of sinking materials and sediment. Lateral advection of suspended particles is needed to balance the fluxes at the three sites. Furthermore, the model suggests that the preservation of biogenic components is lower than at other sites of the Ross Sea, probably due to the low accumulation rates that imply a high residence time of biogenic materials at the sediment-water interface.