Anthropocene Geomorphic Change. Climate or Human Activities?

Key Points Sedimentation rates and frequency of geomorphic disasters show a marked increase worldwide, especially after midtwentieth century This points to an intensification of geomorphic processes, which could be one of the characteristics of the Anthropocene Land surface change caused by human activities, rather than climate change, is very likely behind the intensification of geomorphic processes An analysis of the evolution of sedimentation rates and disasters caused by surface geologic processes during the last century, at a global scale, is presented. Results show that erosion/sedimentation processes and frequency of such disasters increased substantially, especially after midtwentieth century, coinciding with the period of intense change known as the “Great Acceleration.” Increases for this type of disasters are significantly greater than for other disasters related to natural processes, and about 1 order of magnitude in little more than half a century. This implies an important “global geomorphic change.” Comparisons and correlations between changes observed in those processes and potential natural (rainfall) and human (degree of land surface transformation) drivers showed a strong relationship with the latter, and not so clear with the former. This suggests that the intensification of surface geologic processes is most likely due to a greater extent to a land transformation/geomorphic processes coupling than a climate/geomorphic processes one. Plain Language Summary It is usually assumed that geologic processes change extremely slowly, and this is in general the case when considered within a human time frame. However, geologic activity affecting land surface appears to be changing very rapidly. Data gathered in very different parts of the world show that since the end of the nineteenth century, very especially after midtwentieth century, sediment is accumulating more and more rapidly in very different sedimentation environments. This indicates that erosion (and soil loss) is becoming more intense in all sorts of environments and under very varied climate conditions. Also, the frequency of disasters caused by floods and landslides is increasing in a similar manner. Over tenfold increases seem to have taken place in less than a century. Of course, population growth implies greater exposure and therefore higher probability of disasters, but the magnitude of the increase observed can hardly be explained by this. Results point to an intensification of