ABSTRACT

With all the publications about historical disasters and the ongoing debate about a world which seems to be “becoming a more risky place,” we sometimes cherish the illusion that we know enough about how disasters come in series over time. 1 Statistics indicate an increasing number of catastrophic events, but a closer look will show that the time bar often covers only the last fifty to a hundred years. 2 The twentieth century saw unprecedented population growth and thus growing risk exposure for an increasing part of the world’s population. Areas such as the North American Gulf Coast, which were uninhabited or sparsely populated in earlier centuries, have only become urbanized and industrialized in the last sixty years. This process has enhanced exposure to risk, which in turn inevitably raises the fundamental question of whether it is the frequency of natural extreme events that is constantly increasing or just their likelihood to turn into a disaster. Probably it is a combination of both. An important and ongoing challenge for the future will be to collect more information about the history of natural events in order to better understand the processes involved. There is a relatively long history of reconstructing past events in the field of historical climatology. 3 In the case of historical landslides, however, there is no such tradition, even though the risk of landslides is quite common in many areas. This may perhaps be explained by a certain perception threshold, which is probably closely connected to the number of lives lost. One exception in Europe is Italy, where landslides cause more severe damage every year, mainly in the Apennines. 4 Together with earthquakes, floods, and the two major volcanoes, Vesuvius and Etna, mass movements are a serious danger.