Benefits of Dust

Dale W. Griffin and his co-authors ("The Global Transport of Dust," May–June) described the disquieting aspects of the truly awesome levels of windborne movement of soil particles but overlooked positive aspects of this widespread natural phenomenon. It has long been documented that atmospheric fallout, whether wet or dry, contributes significantly to the replenishment of soils that have been depleted of particulate matter and of dissolved nutrients by erosion, especially following logging or other site disturbance. The regionally immense deposits of rich loess soils, for example in the Midwest, are also of aeolian origin. Additionally, iron and other nutrients that enter ocean waters from dust deposition are important for the productivity of marine phytoplankton.

Arthur H. Westing
Putney, Vermont

We do appreciate the positive aspects of dust transport in Earth's atmosphere, but those were not the focus of our article. We have, however, addressed the benefits of dust transport in past articles (Griffin et al., 2001, Aerobiologia 17:203–213; Griffin et al., 2001, Global Change and Human Health 2:20–33).