A Phytolith Supported Biosphere-Hydrosphere Predictive Model for Southern Ethiopia: Insights into Paleoenvironmental Changes and Human Landscape Preferences since the Last Glacial Maximum

Markus L Fischer,Felix Bachofer,Christian Schepers,Asfawossen Asrat,Verena Foerster,Frank Schäbitz,Annett Junginger,Chad L Yost,Henry Lamb,Martin H Trauth,Ines J E Bludau

doi:10.3390/geosciences11100418

Abstract

During the past 25 ka, southern Ethiopia has undergone tremendous climatic changes, from dry and relatively cold during the Last Glacial Maximum (LGM, 25–18 ka) to the African Humid Period (AHP, 15–5 ka), and back to present-day dry conditions. As a contribution to better understand the effects of climate change on vegetation and lakes, we here present a new Predictive Vegetation Model that is linked with a Lake Balance Model and available vegetation-proxy records from southern Ethiopia including a new phytolith record from the Chew Bahir basin. We constructed a detailed paleo-landcover map of southern Ethiopia during the LGM, AHP (with and without influence of the Congo Air Boundary) and the modern-day potential natural landcover. Compared to today, we observe a 15–20% reduction in moisture availability during the LGM with widespread open landscapes and only few remaining forest refugia. We identify 25–40% increased moisture availability during the AHP with prevailing forests in the mid-altitudes and indications that modern anthropogenic landcover change has affected the water balance. In comparison with existing archaeological records, we find that human occupations tend to correspond with open landscapes during the late Pleistocene and Holocene in southern Ethiopia.

Highlights

The formation of the East African Rift System (EARS) led to large topographical
Since specific information about the paleo-vegetation and its effect on the hydrosphere is missing for southern Ethiopia, we present here the results of a Predictive Habitat or Predictive Vegetation Modelling (PVM)
The highest precipitation is recorded in the Southwestern Highlands, while the lowest annual amount is close to the shores of Lake Turkana and the southern Chew Bahir basin

Summary

Introduction

The formation of the East African Rift System (EARS) led to large topographical. The formation of the East African Rift System (EARS) led to large topographical congradient between the dry lowlands of the Omo-Turkana and Chew Bahir basins and the trasts in southern Ethiopia [1] and is responsible for an extreme precipitation gradimoist [2] (Figure 1). Due to thisand topography entSouthwestern between the dryEthiopian lowlands ofHighlands the Omo-Turkana and Chew basins the moist and its position within the global atmospheric circulation the prevailing vegetation is Southwestern Ethiopian Highlands. In the past within the global atmospheric circulation system,bushlands the prevailing vegetation is partitioned intocenturies, a complex mosaic of forests, bushlandsdeandand grasslands [3]. DeSuch human induced landcoverreorganised change may sphere in Ethiopiaboundary [3]. Such human induced landcover change may have ecosysecosystem climatic conditions with subsequent effects onaffected the hydrosphere and tem climatic boundary conditions with subsequent effects on the hydrosphere and potenpotential consequences for the local economy and food security

Methods

Results

Conclusion