The USGS put out a short note following the October 4 dust storm in southern Arizona, noting that two contributing factors to such events are low vegetation cover and disturbance to soil surfaces.
Vegetation contributes to ecological integrity. The presence of plants reduces soil erosion and dust storms, because it keeps the soil intact, reduces wind momentum, and traps moving soil particles. In spaces between the plants, many undisturbed desert soils are naturally armored by hardened physical and biological crusts.
Low vegetation cover can especially be a problem in drought years in abandoned agricultural fields, which are generally dominated by annual plants. This means that the consequences of dust storms, including motor vehicle crashes, are high in a drought year and low in years with more precipitation.