A networking resource devoted to biological soil crusts and the researchers who study them. We will provide a means for international scientists to communicate, share their research, share important news and announcements, ask questions and find collaborators. We will also provide a space for informal writing on research, opinion, and ideas (now seeking posters!).

Saturday, May 28, 2011

"And the wind blows, the dust clouds darken the desert blue, pale sand and red dust drift across the asphalt trails and tumbleweeds fill the arroyos. Good-bye, come again."

The global dust cycle is the most important thing that most people have never heard of. Drylands emit sediment that can be transported long distances. In many cases this is an entirely natural phenomenon, e.g. ancient lake basins tend to be poorly vegetated due to salinity and tend to be full of transportable sediment. When they were lakes they trapped dust, now they expel it. These are often the dust hotspots of the world (e.g., Koren et al. 2006). Land use including tillage and grazing are also major contributors in other cases; desertification and dust emissions are tightly linked (Breshears et al. 2003). These disturbances can turn large areas into dust emitters. Drought, which we expect to be strongly affected by climate change, can also greatly enhance dust emissions across the board (Belnap et al. 2009). Thus, dust can be considered a secondary global change factor.

The obvious impact of dust emissions in rangelands is that fertility is leaving the site (Neff et al. 2005). The less obvious impacts occur sometimes halfway around the world. Some cities regularly experience crippling dust storms which impact human respiratory health and create blinding conditions on roadways. Beijing is an excellent example, where desertification-linked dust storms have gone from a decadal phenomenon to an annual one, even closing airports for days. In the southwest USA, an endemic fungus responsible for valley fever (a disease causing pheumonia-like symptoms) is transported in dust. Some of the more amazing impacts of dusts may be positive on a global scale, in terms of our prospects for sinking carbon. The two great photosynthetic engines of the Earth, the Amazon rainforest and the oceanic phytoplankton, are both subsidized by dust-borne nutrients from drylands (Fung et al. 2000, Koren et al. 2006, Mahowold 2010).

  • Beijing dust storm (Photo: Prof. Zev Levin, Dept. of Geophysics and Planetary Sciences, The Porter School of Environmental Studies, Tel Aviv, Israel)
Recently two excellent papers have appeared in Proceedings of the National Academy of Sciences about dust emissions and their impacts, and to a lesser degree the role of biocrusts as soil stabilizers.

Munson, S.M., Belnap, J., Okin, G.S. 2011. Responses of wind erosion to climate-induced vegetation changes on the Colorado Plateau. Proceedings of the National Academy of Sciences 

Belnap, J., R. L. Reynolds, M. C. Reheis, S. L. Phillips, F. E. Urban, and H. L. Goldstein. 2009. Sediment losses and gains across a gradient of livestock grazing and plant invasion in a cool, semi-arid grassland, Colorado Plateau, USA. Aeolian Research 1:27–43.

Breshears, D. D., J. J. Whicker, C. B. Zou, J. P. Field, and C. D. Allen.  2009. A conceptual framework for dryland aeolian sediment transport along the grassland-forest continuum: Effects of woody plant canopy cover and disturbance. Geomorphology 105: 28-38.

Fung, I.Y., Meyn, S.K., Tegen, I., Doney, S.C., John, J.G., Bishop, J.K.B., 2000. Iron supply and demand in the upper ocean. Global Biogeochemical Cycles 14, 281–295.

Koren, I., Kaufman, Y.J., Washington, R., Todd, M.C., Rudich, Y., Martins, J.V., Rosenfeld, D., 2006. The Bodélé depression: a single spot in the Sahara that provides most of the mineral dust to the Amazon forest. Environmental Research Letters 1, 0140055.

Mahowald, N.M., Kloster, S., Engelstaedter, S., Moore, J.K., Mukhopadhyay, S., McConnell, J.R., Albani, S., Doney, S.C., Bhattacharya, A., Curran, M.A.J., Flanner, M.G., Hoffman, F.M., Lawrence, D.M., Lindsay, K., Mayewski, K.A., Neff, J., Rothenberg, D., Thomas, E., Thornton, P.E., Zender, C.S., 2010. Observed 20th century desert dust variability: impact on climate and biogeochemistry. Atmospheric Chemistry and Physics 10, 10875–10893.

Neff, J. C., R. L. Reynolds, J. Belnap, and P. Lamothe. 2005. Multi-decadal impacts of grazing on soil physical and biogeochemical properties in southeast Utah. Ecological Applications 15:87–95.

1 comment:

  1. I enjoyed this NPR News Update. Wish more folks understood this. Beer guzzling Off-Roaders are going to be the hard core sales.