Landscape Change due to Thousand Years of Iron Ore Production in the Erzberg Area (Styria, Austria)

Iron ore has been mined in the Erzberg area for at least 900 years, possibly as long as 1500 years. This mining history can be divided into three periods of impact on the landscape. Due to the inefficiency of the early smelting techniques and the low production levels, the first period remained free of serious impacts. A huge demand for energy for ore smelting characterized the second period, resulting in supra-regional deforestation for charcoal production. The third period of mechanized surface mining is marked by the creation of large man-made landforms. In the Erzberg area, both historical documentation and modern recording of the mining activities are exceptionally good and provide an opportunity for i) a qualitative identification and description of the associated landscape changes and ii) a first attempt to quantify them. Qualitative analysis of the documents provided a detailed description of how distinct anthropogenic impacts and landforms have emerged, and identified the procedures that caused medieval supra-regional deforestation. A slope exposure opened along a creek allows interpretation of the geomorphic effects of the historical forest depletion. Quantification of the extent of deforestation was carried out for a forest area close to the mining site. The results allow a reconstruction of the condition of the forest at this site over two centuries. For quantification of the earth material moved by man in mechanized surface mining denudation rates for the Erzberg site were computed and compared with the sediment budget of a nearby river catchment. This comparison suggests that on the local scale man is two to three orders of magnitude more effective in transforming the landscape than geomorphic processes.