Environmental changes and the rise and fall of civilizations in the northern Horn of Africa: An approach combining δD analyses of land-plant derived fatty acids with multiple proxies in soil

Abstract

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Review of the Historic Trajectory of Deforestation, its Drivers and Implications in Ethiopia

“…Both [7,17] reported thick vegetation cover of likely Podocarpus -Juniperus mixed montane forest to have existed on the plateau of northern Ethiopia in the early Holocene (> 500 BC). During the last millennium BC, the climax vegetation in Tigray and Wollo highlands were dry evergreen montane forest, much the same as the few forest relicts seen today in this and central Ethiopia [17,18], and were hosting diverse wildlife species including elephants [20]. Today, very small relict forests exist in this part of Ethiopia, clustering around old churches, in monasteries and in few inaccessible sites [2,17,19], and anthropogenic deforestation being the main reason for their decline [2,8,17].…”

Enhanced continental weathering (δ7Li,εNd) during the rise of East African complex polities: an early large-scale anthropogenic forcing?

“…BP [Gebru et al, 2009, Terwilliger et al, 2013, 2011Figure 3c, d]. Other proxies such as hydrogen (HI) and oxygen (OI) indices from Rock-Eval pyrolysis also indicated intense chemical alteration of organic matter due to agricultural humidification processes and/or human-induced fires [Terwilliger et al, 2013[Terwilliger et al, , 2011. Such extensive anthropogenic landscape management had a major impact on the pedogenic system, leading to an increase of soil leaching, and potentially explaining the decrease of δ 7 Li values during this period.…”

“…As previously shown in Bastian & Mologni et al [2021] and Mologni et al [2020], this may result from low fluvial transport of fine-grained sediments still active during arid climates, since more that 80% of the sediment deposited at the NDSF originates et al, , Terwilliger et al, 2011; (e) δ 13 C of Mai Maikden (MMIII, green line) and Adi Kolen (AKIII, brown line) soil profiles [Gebru et al, 2009, Terwilliger et al, 2011, 2013. Changes in: (f) Human culture [after Fattovich, 2010, Hensel et al, 2019, Ménard et al, 2014, Phillipson, 2012, (g) Subsistence economy [after Bard et al, 2000, Boardman, 1999, (h) Vegetation [after Darbyshire et al, 2003, Terwilliger et al, 2013, Jaeschke et al, 2020 across the Ethiopian highlands. of the East African Rift System created the ideal living conditions for early hominins and for the preservation of their remains [WoldeGabriel et al, 2001].…”

“…Organic proxy investigations of soil profiles from the headwaters region of the Atbara/Tekeze rivers (Adi Kolan=AKIII, Mai Maikden=MMIII; Figure 1b) revealed a strong increase in land clearing and anthropogenic fire activity between ∼3000 and ∼2000 years cal. BP [Gebru et al, 2009, Terwilliger et al, 2013, 2011Figure 3c, d]. Other proxies such as hydrogen (HI) and oxygen (OI) indices from Rock-Eval pyrolysis also indicated intense chemical alteration of organic matter due to agricultural humidification processes and/or human-induced fires [Terwilliger et al, 2013[Terwilliger et al, , 2011.…”

“…This record cover to the period associated with the rise of the first East African complex polities, namely the Pre-Aksumite cultures (∼3 to ∼2 ka BP) and the Aksumite Kingdom (∼2 to ∼1 ka BP) that proceeded it [Fattovich, 2010, Phillipson, 2012, which are contemporaneous with the Ancient Egyptian Dynastic, Ptolemaic and Ro-man civilizations [Manning et al, 2017]. In addition to discussing original data on marine sediments, we use a wealth of information provided by a number of Holocene paleo-pedological [Bard et al, 2000, Gebru et al, 2009, Terwilliger et al, 2013, 2011, archaeological and paleoclimatic [Costa et al, 2014, Jaeschke et al, 2020 investigations conducted in the Ethiopian Highlands to discuss potential impacts of intensified land-use by Aksumite and Late Egyptian complex polities on sediment transport and chemical weathering intensity.…”