Lakeside View: Sociocultural Responses to Changing Water Levels of Lake Turkana, Kenya

Throughout the Holocene, Lake Turkana has been subject to drastic changes in lake levels and the subsistence strategies people employ to survive in this hot and arid region. In this paper, we reconstruct the position of the lake during the Holocene within a paleoclimatic context. Atmospheric forcing mechanisms are discussed in order to contextualize the broader landscape changes occurring in eastern Africa over the last 12,000 years. The Holocene is divided into five primary phases according to changes in the strand-plain evolution, paleoclimate, and human subsistence strategies practiced within the basin. Early Holocene fishing settlements occurred adjacent to high and relatively stable lake levels. A period of high-magnitude oscillations in lake levels ensued after 9,000 years BP and human settlements appear to have been located close to the margins of the lake. Aridification and a final regression in lake levels ensued after 5,000 years BP and human communities were generalized pastoralists-fishers-foragers. During the Late Holocene, lake levels may have dropped below their present position and subsistence strategies appear to have been flexible and occasionally specialized on animal pastoralism. Modern missionary and government outposts have encouraged the construction of permanent settlements in the region, which are heavily dependent on outside resources for their survival. Changes in the physical and cultural environments of the Lake Turkana region have been closely correlated, and understanding the relationship between the two variables remains a vital component of archaeological research

Modelling Exchanges: From the Process Scale to the Regional Scale

International audienceThis chapter shows how the knowledge on the processes of surface exchange and atmospheric fate of different pollutants from agriculture or with an impact on agroecosystems is factored into mathematical simulation tools. It also considers the complexity of the interactions involved, the quantities of matter exchanged between agroecosystems and the atmosphere, and the measurement methods used to quantify them. The resulting models, which range from highly local (plant, leaf …) to global scales, ultimately enable to assess the impacts of changes in agricultural practices or climate change on pollutant exchanges between the atmosphere and agroecosystems. We describe different modelling approaches at the process, field, landscape and regional scales with different integrative levels. Model results are useful to understand how different processes interact and to predict how different environmental conditions, future climate or agricultural practices affect air quality. Models can also help identify levers for emission mitigation and estimate their efficiency