Undercover cropland expansion in forests of Bale Mountains, Ethiopia: Revealed with satellite remote sensing combined with ground photos
2 Remote Sensing Unit, Department of Geography, University of Wuerzburg, Am Hubland, 97074 Wuerzburg,
3 University of Bayreuth, Faculty of Biology, Chemistry and Earth Sciences, Professorship of Disturbance Ecology, Universitätsstraße 30, 95440 Bayreuth.
O 3.5 in Research Yields: Ideas Pursued to the End
10.10.2013, 16:30-16:45, H6, GEO
With the increasing global population and demand for food products, rapid cropland expansion is becoming a common phenomenon in the tropical countries potentially threatening supplies of ecosystem services. Ethiopia is one of such countries that showed large increment in the area of land cropped in the past decades. Coupled with increasing population and poor technology in the country as well as recent leasing of moderate slope land suitable for growing crops, local farmers are being forced to expand cropland to the remaining unoccupied mountains which have been originally forests and meadows. One of the mountain ecosystems that are under continuous pressure due to cropland expansion in the past decades is the Bale Mountains of Ethiopia. Recent trends in cropland expansion in the Bale Mountains has typical pattern of forest-crop mixture which is similar to traditional agro-forestry systems. Traditional agroforestry systems have been common practices mainly in the southern and southwestern parts of Ethiopia. This involves growing of different vegetation layers that include multipurpose trees, crops like maize, fruit trees, and vegetables. The distinct feature of the cropland expansion in the Bale Mountains is the reason that it emerged as an undercover cropland expansion inside forests (e.g. J. procera forest) due to desperate needs for food crops under government restriction for clearing remnants of forests. Though the pattern of growing crops under forest canopies temporarily preserves the forest, it could gradually reduce the forest cover and results in death of trees due to continuous tillage. Moreover, the services provided from the forest (e.g. erosion regulation) could be reduced though crop production increases especially in the extremely steep terrains. Therefore, the potential impact on the supply of ecosystem services and their tradeoffs need to be assessed for introducing sustainable management practices in the mountainous terrains of Bale. For such analysis, the hidden expansion of croplands inside forests need to be mapped and hence various mapping techniques have to be tested and implemented. Airborne and spaceborne remote sensing data have been widely used for land use/cover classification and mapping at various scales. However, this is mainly based on mapping of canopy structure that is visible from above. Detailed analysis is thus essential to capture the hidden undercover cropland expansion inside forests. In this study we combined satellite remote sensing data with ground photos to map undercover cropland expansion inside forests and assess its implications on ecosystem services in the hilly terrains of Bale Mountains of Ethiopia. Results showed that cropland expansion under forest canopies increases food provisioning services while it hinders supplies of erosion control services through increased risk of erosion. Moreover, the study demonstrated that ground photos enable detection of undercover cropland expansion inside forests which would otherwise be underestimated when satellite images are used.
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