Erosion-driven environmental degradation in Tigray, Ethiopia
Abstract
The Tigray Plateau of Northern Ethiopia is a key region for the study of relationships between climate, land use and the rise and fall of complex societies. Tigray has been the home to a succession of highly developed and powerful kingdoms and has a long history of agriculture, dating back to ~ 6,000 yrs BP. Unfortunately its mountainous topography makes the region particularly susceptible to accelerated erosion and mass wasting from intense land use practices and its location along the ITCZ and the East African rift system make the area prone to climatic changes. Today, after 6,000 years of agriculture, of which the last ~3,000 years have involved intense land use, the once fertile Tigray region is now highly degraded with frequent famine and some of the highest rates of soil erosion in the world. We find, based on a comparison of background (long-term) and anthropogenic short-term time-averaged erosion rates that deforestation and a transition to cropland farming likely increased rates of localized upstream erosion and downstream deposition by up to an order of magnitude greater than the natural background rates. We define three distinct periods of note in terms of rates and patterns of Holocene erosion and deposition in the east Tigray Plateau of Ethiopia. First, we take note of the depositional record and paleo-flaural reconstructions of a time of regional climate change yet little landuse change in Ethiopia, 7,500 - 6,000 cal yr BP (Late Prehistory and the beginning of the migration of peoples out of the Sahara and into Sudan and the highlands of Ethiopia). Second, we look at the stratigraphic record of the beginning of intense landuse and cultivation in the gently sloping lowland areas, 3200 -2300 Cal yrs BP (Pre-Aksumite period and the establishment of the first large centralized government in the upper Highlands). Third, we identify from the geological record a period of deforestation and farming of higher elevation, steep sloped hillsides and terraces 2300 -1300 Cal yrs BP (a period spanning the rise and subsequent fall of the Aksumite kingdom.)
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMEP43E0691S
- Keywords:
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- 0439 BIOGEOSCIENCES / Ecosystems;
- structure and dynamics;
- 1625 GLOBAL CHANGE / Geomorphology and weathering;
- 1803 HYDROLOGY / Anthropogenic effects;
- 1815 HYDROLOGY / Erosion