The ecology of dust

© The Ecological Society of America www.frontiersinecology.org F many scientists, the only dust they think about is the thin film of material that accumulates on their computer monitor on a regular basis. However, dust has enormous relevance to a wide range of ecological processes and environmental management challenges. Dust is fine particulate material that is removed from the land surface by wind erosion and is small enough to be suspended in the atmosphere (Bagnold 1941; Toy et al. 2002). Dust emissions vary with climate, as shown by paleo-studies (eg Clark et al. 2002), and also with land use. Perhaps the most notable example of how ecologically important dust can be is the Dust Bowl era of the 1930s in the American Great Plains, which is considered by many experts to be one of the most severe environmental catastrophes in the history of the US (eg Peters et al. 2007). The widespread cultivation of marginally arable lands, in conjunction with a severe regionalscale drought during the 1930s, caused substantial increases in wind-erosion rates, resulting in the degradation of roughly 90 million ha of land (Utz et al. 1938) and the loss of nearly 800 million metric tons of topsoil in 1935 alone (Johnson 1947; Hansen and Libecap 2004). This largescale amplification of wind erosion was the result of small fields becoming more erosive and interconnected (Hansen and Libecap 2004), thereby triggering a threshold response (Peters et al. 2007). The devastating effects of the Dust Bowl were felt nationally and resulted in the formation of the Soil Conservation Service in 1935. However, the important ecological lessons of the Dust Bowl have faded with time, and most ecological studies do not explicitly consider the impact of dust flux and wind erosion. Ironically, the former Soil Conservation Service – now the Natural Resources Conservation Service – has shifted most of its focus to water erosion, and has largely abandoned the problem of wind-caused erosion (Field et al. 2009). Environmental scientists are increasingly recognizing dust as both a major environmental driver and a source of uncertainty for climate models (Tanaka and Chiba 2006; Neff et al. 2008). Wind erosion and dust emissions can cause substantial impacts, not only to human health (eg through respiratory problems), but also to basic ecosystem processes, at scales ranging from individual plants or even smaller (Figure 1a) up through local and regional scales (Figure 1b and c) to a global scale (Figure 1d), representing biogeochemical connectivity across continents (Peters et al. 2007; Okin et al. 2009). Here, we provide a primer on the importance of aeolian (wind-driven) processes associated with wind erosion, as REVIEWS REVIEWS REVIEWS