Vegetational and climatic changes at the northern fringe of the sahara 250,000–5000 years BP: evidence from 4 marine pollen records located between Portugal and the Canary Islands

Hooghiemstra, H.; Stalling, H.; Agwu, Chiori O C; Dupont, Lydie M

doi:10.1016/0034-6667(92)90137-6

Cited by 172 publications

(92 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…These distributions suggest that, during the early Holocene, the Sahara was a savannah with riparian corridors linking north and south. Patches of more arid terrain in mountain rainshadows may better explain the arid pollen found in North Atlantic cores (8).…”

Section: African Humid Period Biogeography and Palaeohydrologymentioning

confidence: 99%

“…For example, genetics indicates that the Sahara has been a barrier to the dispersal of Macroscelidea (elephant shrews) since the late Miocene when the desert first formed (6), whereas pollen analysis of terrestrial sediments from the central Sahara demonstrates that during the Holocene humid period an arid belt existed north of 22° (7). Furthermore, arid plant taxa are found continuously through Atlantic Ocean cores between 23°and 27°north for the last 250 ka suggesting a longlasting Saharan arid belt at this latitude (8). In contrast, a green Sahara route has been proposed whereby this currently hyperarid region could have been habitable during "green" periods of greater humidity (9,10).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Ancient watercourses and biogeography of the Sahara explain the peopling of the desert

Drake

Blench

Armitage

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

410

327

View full text Add to dashboard Cite

Evidence increasingly suggests that sub-Saharan Africa is at the center of human evolution and understanding routes of dispersal “out of Africa” is thus becoming increasingly important. The Sahara Desert is considered by many to be an obstacle to these dispersals and a Nile corridor route has been proposed to cross it. Here we provide evidence that the Sahara was not an effective barrier and indicate how both animals and humans populated it during past humid phases. Analysis of the zoogeography of the Sahara shows that more animals crossed via this route than used the Nile corridor. Furthermore, many of these species are aquatic. This dispersal was possible because during the Holocene humid period the region contained a series of linked lakes, rivers, and inland deltas comprising a large interlinked waterway, channeling water and animals into and across the Sahara, thus facilitating these dispersals. This system was last active in the early Holocene when many species appear to have occupied the entire Sahara. However, species that require deep water did not reach northern regions because of weak hydrological connections. Human dispersals were influenced by this distribution; Nilo-Saharan speakers hunting aquatic fauna with barbed bone points occupied the southern Sahara, while people hunting Savannah fauna with the bow and arrow spread southward. The dating of lacustrine sediments show that the “green Sahara” also existed during the last interglacial (∼125 ka) and provided green corridors that could have formed dispersal routes at a likely time for the migration of modern humans out of Africa.

show abstract

Section: African Humid Period Biogeography and Palaeohydrologymentioning

confidence: 99%

mentioning

confidence: 99%

Ancient watercourses and biogeography of the Sahara explain the peopling of the desert

Drake

Blench

Armitage

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

410

327

View full text Add to dashboard Cite

show abstract

“…However, pollen and macro-fossil evidence shows that boreal forest extended farther north than today in the mid-Holocene Prentice et al, 2000;Binney et al, 2017) and, except in Alaska and central Canada, extended to the Arctic coast during the LIG LIGA, 1991;Lozhkin and Anderson, 1995). Pollen and other biogeographical/geomorphological and paleohydrological evidence also indicates northward extension of vegetation into modern-day desert areas, particularly in northern Africa, both in the mid-Holocene (Drake et al, 2011;Hély et al, 2014;Larrasoana et al, 2013;Lezine et al, 2011;Prentice et al, 2000;Tierney et al, 2017) and during the maximum phase of the LIG (Castaneda et al, 2009;Hooghiemstra et al, 1992). Given the impact of increased woody cover on albedo and evapotranspiration, these vegetation changes should have profound impacts on the surface energy and water budgets and may help to explain mismatches between simulated and reconstructed high-latitude (Muschitiello et al, 2015) and monsoon climates Claussen and Gayler, 1997;Pausata et al, 2016) in both time periods.…”

Section: Sensitivity To Prescribed Vegetationmentioning

confidence: 99%

The PMIP4 contribution to CMIP6 – Part 2: Two interglacials, scientific objective and experimental design for Holocene and Last Interglacial simulations

et al. 2017

View full text Add to dashboard Cite

Abstract. Two interglacial epochs are included in the suite of Paleoclimate Modeling Intercomparison Project (PMIP4) simulations in the Coupled Model Intercomparison Project (CMIP6). The experimental protocols for simulations of the mid-Holocene (midHolocene, 6000 years before present) and the Last Interglacial (lig127k, 127 000 years before present) are described here. These equilibrium simulations are designed to examine the impact of changes in orbital forcing at times when atmospheric greenhouse gas levels were similar to those of the preindustrial period and the continental configurations were almost identical to modern ones. These simulations test our understanding of the interplay between radiative forcing and atmospheric circulation, and the connections among large-scale and regional climate changes giving rise to phenomena such as land-sea contrast and highlatitude amplification in temperature changes, and responses of the monsoons, as compared to today. They also provide an opportunity, through carefully designed additional sensitivity experiments, to quantify the strength of atmosphere, ocean, cryosphere, and land-surface feedbacks. Sensitivity experiments are proposed to investigate the role of freshwater forcing in triggering abrupt climate changes within interglacial epochs. These feedback experiments naturally lead to a focus on climate evolution during interglacial periods, which will be examined through transient experiments. Analyses of the sensitivity simulations will also focus on interactions between extratropical and tropical circulation, and the relationship between changes in mean climate state and climate variability on annual to multi-decadal timescales. The comparative abundance of paleoenvironmental data and of quantitative climate reconstructions for the Holocene and Last Interglacial make these two epochs ideal candidates for systematic evaluation of model performance, and such comparisons will shed new light on the importance of external feedbacks (e.g., vegetation, dust) and the ability of state-of-the-art models to simulate climate changes realistically.

show abstract

“…After the Younger Dryas, oak (Quercus) forests dominated the north and central part of western Iberia, as revealed by the marine near-shore pollen record (Hooghiemstra et al, 1992;Desprat et al, 2003;Turon et al, 2003). Vegetation will remain essentially unchanged and added in the studied area by chestnuts (Castanea) and pines (Pinus) till the Middle Ages (Gonc -alves, 1989).…”

Section: Evolution Previous To the Christian Reconquestmentioning

confidence: 96%

Natural to anthropogenic forcing in the Holocene evolution of three coastal lagoons (Caldas da Rainha valley, western Portugal)

Dinis

Henriques

Freitas

et al. 2006

Quaternary International

View full text Add to dashboard Cite

In the coast of Central Portugal three lagoons were created by the Holocene flooding of diapiric-related depressions but experienced afterwards a significant sediment accumulation. Fast environmental and morphological changes after the Middle Holocene were clearly forced by anthropogenic activities since the Middle Ages and show a strong feedback on the human communities. Erosion in the studied watersheds depends on climatic and anthropic changes; especially, demographic rises increase agriculture and deforestation in the watersheds, and sedimentation in the lagoons. The region was successively occupied by ethnic groups since the Neolithic (including Romans, Sueves, Visigoths and Muslims), but the main changes were largely due to anthropic forcing following the Christian Reconquest by the Kingdom of Portugal. In fact, during the Middle Ages and Renaissance the area had intense nautical, fishing and agricultural activities, even if reduced during the 14th century crisis. Later, due to severe sediment accumulation and shoaling, sailing was drastically reduced and most of the area drowned in the maximum transgression was claimed to farming. It is also noteworthy that the social evolution and sediment entrainment in the watersheds appear to be in tune with climatic trends deduced after regional and global data. In synthesis, we conclude that the human activities during the last millennium greatly accelerated the natural silting trend of the lagoons. r

show abstract

Vegetational and climatic changes at the northern fringe of the sahara 250,000–5000 years BP: evidence from 4 marine pollen records located between Portugal and the Canary Islands

Cited by 172 publications

References 31 publications

Ancient watercourses and biogeography of the Sahara explain the peopling of the desert

Ancient watercourses and biogeography of the Sahara explain the peopling of the desert

The PMIP4 contribution to CMIP6 – Part 2: Two interglacials, scientific objective and experimental design for Holocene and Last Interglacial simulations

Natural to anthropogenic forcing in the Holocene evolution of three coastal lagoons (Caldas da Rainha valley, western Portugal)

Contact Info

Product

Resources

About