Desertification

Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become arid. It is the spread of arid areas caused by a variety of factors, such as climate change and overexploitation of soil as a result of human activity. Throughout geological history, the development of deserts has occurred naturally. In recent times, the potential influences of human activity, improper land management, deforestation and climate change on desertification is the subject of many scientific investigations. As recently as 2005, considerable controversy existed over the proper definition of the term "desertification." Helmut Geist (2005) identified more than 100 formal definitions. The most widely accepted of these was that of the Princeton University Dictionary which defined it as "the process of fertile land transforming into desert typically as a result of deforestation, drought or improper/inappropriate agriculture". This definition clearly demonstrated the interconnectedness of desertification and human activities, in particular land use and land management practices. It also highlighted the economic, social and environmental implications of desertification.However, this original understanding that desertification involved the physical expansion of deserts has been rejected as the concept has evolved. Desertification has been defined in the text of the United Nations Convention to Combat Desertification (UNCCD) as "land degradation in arid, semi-arid and dry sub-humid regions resulting from various factors, including climatic variations and human activities according to Hulme and Kelly, (1993)." There exists also controversy around the sub-grouping of types of desertification, including, for example, the validity and usefulness of such terms as "man-made desert" and "non-pattern desert". The world's most noted deserts have been formed by natural processes interacting over long intervals of time.

Winter post-droughts amplify extreme nitrate concentrations in German rivers

Winter post-droughts amplify extreme nitrate concentrations in German rivers