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

今天，撒哈拉作为世界上最大的热沙漠，将北方非洲分成两部分，而绿色撒哈拉促进了地中海和热带雨林在全新世早期和中期的相互作用。伴随的古生态变化意味着资源的变化，从而影响生存战略。因此，环境的变异性既是一个重要的限制因素，也是非洲内部跨区域接触和人类社会战略及其流动模式的驱动力。第二阶段的目标是采用第一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SPP 2143内联合合作的发现中发展出来的考古研究问题。很明显，景观生物资源是区域间联系的主要决定因素，因此，在时空尺度上查明这些资源是关键，该项目的重点是乍得共和国的两个生态有利地区，这两个地区为孢粉学和地球化学分析提供了沉积档案：（1）撒哈拉中部Ounianga以东的地下水绿洲（19°N）和（2）萨赫勒地区现今乍得湖以东的Kanem地区（14-15°N），其沙丘间洼地经常被湿地占据。将建立一个时间框架的古环境变化，在此期间，这些地下水绿洲和他们的经济developed.The北方网站沿着Ounianga悬崖充当绿洲，因为中全新世去绿化的撒哈拉沙漠，而南部的Kanem地区的网站提供绿洲的见解，因为大约4200卡BP的大乍得湖的衰落，直到今天。因此，这项研究为了解（1）古生态变化的时空表现，（2）地下水绿洲遗址的开发，以及（3）土地利用随时间的变化提供了独特的机会。SPP 2143将受益于这些超区域尺度的洞察力，因为它们从这个过境区域呈现出可见的多层纠缠。

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.