‘De-Greening’ of the central Sahara – northern Sahel: Holocene environmental dynamics and oases economies between 14-19°N (DeGree)

今天的撒哈拉，作为世界上最大的热沙漠，将北非分成了两部分，而绿色的撒哈拉在全新世早期和中期促进了地中海和雨林之间的相互作用。伴随的古生态变化意味着资源的变化，从而影响生存策略。因此，环境变化既是非洲内部跨区域接触和人类社会战略及其流动模式的重要限制因素，也是推动因素。第二阶段的目标是遵循第一个资助阶段的基本方法，利用沉积档案来破译全新世环境动力学，并更加强调从SPP2143联合合作的发现中发展出来的考古研究问题。景观生物资源是区域间联系的主要决定因素，因此在时空尺度上对其进行识别是关键。该项目的重点是乍得共和国两个生态有利的地区，为孢粉学和地球化学分析提供沉积档案：(1)撒哈拉中部（北纬19°）乌尼昂加以东的地下水绿洲；(2)萨赫勒地区目前乍得湖以东的卡内姆地区（北纬14-15°），其间洼地经常被湿地占据。在这些地下水绿洲及其经济发展的时期内，将建立古环境变化的时间框架。沿着乌尼昂加悬崖的北部遗址自全新世中期撒哈拉沙漠去绿化以来一直是绿洲，而卡内姆地区的南部遗址则提供了自4200年前左右大湖乍得湖消退至今的绿洲。因此，这项研究为了解(1)古生态变化的时空特征，(2)地下水绿洲遗址的发展，以及(3)土地利用随时间的变化提供了独特的机会。SPP2143将从这些超区域尺度的见解中受益，因为它们可以从这个过境区域看到多层纠缠。

Today the Sahara, as the world’s largest hot desert, separates northern Africa into two parts, while a Green Sahara facilitated interactions during early and mid-Holocene between the Mediterranean and rainforest. Concomitant palaeoecological shifts imply changing resources, thereby affecting subsistence strategies. Environmental variability thus represents both, an important limiting factor as well as a driving force for inner-african transregional contacts and strategies of human societies and their mobility patterns. The goal of the second phase pursues the basic approach from the first funding phase in using sedimentary archives to decipher Holocene environmental dynamics with a stronger emphasis to archaeological research questions that have developed from the findings of the joint collaboration within the SPP2143. It became obvious that biotic resources of landscapes are a major determinant for interregional contacts and thus their identification on a spatiotemporal scale are key.The project’s focus is on two ecologically favourable areas from the Republic of Chad that provide sedimentary archives for palynological and geochemical analyses: (1) The groundwater oases east of Ounianga within the central Sahara (19°N) and (2) the Kanem Region east of present Lake Chad in the Sahel (14-15°N) with its interdunal depressions that are often occupied by wetlands. A chronological framework of palaeoenvironmental changes will be established for a time period during which these groundwater oases and their economies developed.The northern sites along the Ounianga escarpment acted as oases since the mid-Holocene de-greening of the Sahara whereas the southern sites of the Kanem Region provide oases insights since the fading of the Mega-Lake Chad around 4200 cal BP until today. This research thus provides unique opportunities for understanding of (1) the spatio-temporal appearance of palaeoecological shifts, (2) the development of groundwater oases sites, as well as (3) land use changes through time. The SPP2143 will benefit from these insights on a supra-regional scale as they render visible multi-layered entanglements from this region of transit.