Vegetation and climate history of Yemen

The vegetation and climate history of southern Yemen

Light brown Holocene silt deposited at the confluence of the Wadi Sana and Wadi Shumylya. These silt deposits preserve a sequence of early to mid-Holocene archaeological sites in what is now a sparsely inhabited region of southern Yemen. Note car in the middle background at the foot of the Khuzmum butte.

Collaborators:
Kenneth L. Cole, USGS Colorado Plateau Research Station
Joy McCorriston, Department of Anthropology, The Ohio State University
Subir Banerjee, Department of Geology and Geophysics, University of Minnesota
Eric Oches,Department of Geology, University of South Florida
Abdalaziz Bin ‘Aqil, Mukalla Museum, Yemen
Louise Martin, Institute for Archaeology, University College, London
A.G. Miller, Royal Botanic Garden, Edinburgh, Scotland

Summary:
This research is a reconstruction of the past vegetation of Yemen using fossil deposits left in caves and crevices by a small mammal called the rock hyrax. This is part of a series of interrelated projects in archaeology, geology and paleoecology that are studying the history of an area in the remote Hadramawt region of Yemen, on the southern tip of the Arabian Peninsula. This research is coordinated through the Roots of Agriculture in Southern Arabia (RASA) program, headed by Dr. Joy McCorriston, the Yemeni Ministry of Antiquties, and the American Institute for Yemeni Studies. Funding for this portion of the project is primarily from the U.S. National Science Foundation.

While other investigators are concentrating on the abundant archaeological or geological deposits, the role of the USGS researcher, Dr. Kenneth Cole, is to reconstruct the past vegetation and climate of the area. Plant fossils have been found in the abundant middens left in the steep limestone cliffs by rock hyraxes (Procavia spp.). The rock hyrax, or "wabar", leaves midden deposits of urine, feces, and plant parts in caves and shelters called hyraceum. These hyrax middens are remarkably similar to packrat middens which are abundant in the arid portions of the western North America. The hyrax middens analyzed thus far from the site range in age between 5200 and 2100 years. This covers the time period during which few archaeological sites are known from the area probably because of the hyper-arid climate.

This project will reconstruct the vegetational history through plant macrofossils and pollen contained within the middens in order to understand the climatic changes taking place in the area and the possible impacts of domesticated animals (primarily goats and camels) on the vegetation. Early mid-Holocene (roughly 7500 to 6000 years ago) archaeological sites suggest that the climate at that time was considerably wetter than at present. Midden results thus far document an interval of extreme aridity between 4600 and 2500 yr B.P. The biennial precipitation regime, the use of domesticated animals, and plateau topography of the Hadramawt Province are remarkably similar to the Colorado Plateau region of western North America. This project will integrate with studies of the effects of past and future global climate changes in similar desert areas.

	A cave in a limestone cliff where several hyrax middens were found. Some of the few plants growing here can be seen at lower left.
	A hyrax midden deposited on a shelf in a cave. A partially decomposed camel lay just out of the picture to the left inspiring the rapid excavation of this midden.

A few fossils from hyrax middens demonstrate the excellent preservation. (Click on images to view more details.)

	Modern and fossil seeds of Acacia ehrenbergiana
	Modern and fossil seeds of Citrillus colocynthus
	Linen cloth and a possible human finger bone from a 2100 year old deposit; remains of what may have been a mummy within the cave where the midden was found.

	Closeup of the head of a fossil tick.

Abstract of 2001 Presentation for Ecological Society of America

Other Web Sites with Information on this project:

Holocene Climate Change and Human Impact on the Landscape,
Wadi Shumylya, Yemen

Ken Cole's home page

Colorado Plateau Research Station home