KEYNOTE: DIRT AND THE KING OF FISH: GEOMORPHOLOGY, BIOLOGY, AND PEOPLE IN THE 21ST CENTURY

The development of sustainable agriculture and conservation of endangered species are two of the most fundamental challenges facing society in the present century. The history of interactions between geomorphology, biology, and human societies provides insight into these challenges. In particular, the historical record of salmon management in Europe, New England and the Pacific Northwest indicates that there is substantial need to incorporate geomorphic insights on the effects of changes in watershed processes into salmon recovery efforts. Natural and anthropogenic influences on watershed processes affect the distribution and abundance of salmon across a wide range of spatial and temporal scales, from differences in species use and density between individual pools and riffles to regional patterns of threatened, endangered, and extinct runs. The specific impacts of human activities (e.g., mining, logging, and urbanization) vary among regions and watersheds, as well as between different channel reaches in the same watershed. Understanding of both disturbance history and key biophysical processes are important for diagnosing the nature and causes of differences between historical and contemporary fluvial and watershed conditions based on evaluation of both historical and spatial contexts. Soil erosion played a role in the demise of ancient civilizations of Neolithic Europe, Classical Greece, Rome, and Central America. In each case, a pattern of slow, steady population growth while farms filled in the landscape was followed by several hundred to at most a thousand years of stability before a rapid population crash—time scales comparable to those for soil erosion under agricultural land uses. Assessment of contemporary imbalances between rates of soil production and erosion in agricultural settings shows that the threat of soil erosion is not just as ancient history. Sustaining agricultural output requires sustaining soil fertility by eroding soil no faster than soil forms. The simple fact that rates of soil erosion in agricultural settings greatly exceed rates of soil production appears to be a major driving force in the lifecycle of civilizations.