The global change of continental aquatic systems: dominant impacts of human activities

Abstract

Continental aquatic systems, particularly rivers, are exposed to major changes due to human pressures. Some changes are voluntary such as flow regulation and the fragmentation of river courses, both due to damming, or the water consumption particularly in dry regions, which results in a partial to complete dry-up of some rivers (neo-arheism). Other changes result from indirect impacts of other human activities, and include: sediment unbalance of river systems, chemical contamination, acidification, eutrophication, thermal unbalance, radioactive contamination, microbial contamination, and aquatic species introduction/invasion. These changes can be regarded as syndromes which have now reached a global amplitude, even in less populated regions, as the result of damning, mining and of long-range atmospheric pollution, thus defining a new era, the Anthropocene, where continental aquatic systems are no longer controlled by earth systems processes but by human activities. Each region of the globe has developed specific patterns of syndromes trajectories that can be reconstructed from historical analysis and through environmental archives. These trajectories reveal multiple types of human responses to aquatic environmental issues (e.g. water quality), usually lasting 10 to 50 years for the successful ones. The reactions of the earth system to such major changes of fluxes (water, energy, nutrients, carbon, pollutants) via the continental waterscape, the land-ocean interactions, the water bodies-atmosphere interactions, are likely to take place over a longer time scale (100-1,000 years) yet are poorly addressed by scientists and not considered in Integrated Water Management, particularly as concerns the coastal zone.