Land degradation drivers of anthropogenic sand and dust storms

Sand and Dust Storms (SDS) are often considered as a natural phenomenon typical of the remote desert regions. It is becoming clear, however, that human activities also contribute to the increasing global impacts of SDS. The United Nations Convention to Combat Desertification has recently recognized the global relevance of the anthropogenic SDS sources. These are directly and/or indirectly linked to human activities that make the soils more susceptible to wind erosion, such as unsustainable agricultural practices, overgrazing, deforestation, and misuse of water resources: in other words, the drivers of land degradation. Human activities that contribute to climate change can also be considered as indirect drivers of SDS, as they affect SDS factors like drought patterns and wind regimes. Although the contribution of anthropogenic source areas to total global dust emissions is relatively limited as amount of dust emitted (19–25%), these sources are widespread in almost all environments including drylands, sub-humid and humid areas, and high latitudes. This article reviews the scientific evidence on the contribution of anthropogenic activities to SDS generation in a variety of SDS hotspots. The contexts considered in this study are associated with different levels of aridity (arid to humid) and with a wide range of land use systems and management practices, human drivers, and land health conditions. On one extreme, like in the Thar Desert of India, SDS are a manifestation of chronic and extensive historical land degradation in arid climatic conditions. On another extreme SDS are occasional events caused by a combination of exceptional weather conditions (e.g., drought spells, windstorms) and of factors increasing soil erodibility locally (e.g., bare fallow or soil disturbance after harvest) and in specific times of the year, as often observed in humid central Europe. Drivers linked to technological activities such as mining, industry, and military operations were also reviewed. Anthropogenic source areas are often of smaller size compared to the natural ones and marked by more scattered distribution patterns. SDS originated from these sources are in some cases occasional and relatively small but can have severe or cumulative impacts on local communities, local residential and transportation structures, and on downwind urban areas. The majority of SDS studies have mostly addressed large scale events and rarely addressed the distinction between natural and anthropogenic sources. The relationships between the observed impacts of the SDS events and the respective drivers have been poorly studied, as well as the interactions among the SDS drivers, also due to the lack of high resolution and field data on land use and land degradation conditions in the dust source areas. More in-depth research would be needed to understand to what extent the increasing frequency and severity of anthropogenic SDS can be considered as indicators of increasing desertification and reduced land resilience to climate change.