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Soil erosion is an important process in dryland ecosystems, yet measurements and comparisons of wind and water erosion within and among such ecosystems are lacking. Here we compare wind erosion and transport field measurements with water erosion and transport from rainfall-simulation for three different semi-arid ecosystems: a shrubland near Carlsbad, New Mexico; a grassland near Denver, Colorado; and a forest near Los Alamos, New Mexico. In addition to comparing erosion loss from an area, we propose a framework for comparing horizontal mass transport of wind- and water-driven materials as a metric for local soil redistribution. Median erosion rates from wind for vertical mass flux measurements (g m(-2) d(-1)) were 1.5 X 10(-2) for the shrubland, 8.3 x 10(-3) for the grassland, and 9.1 x 10(-3) for the forest. Wind-driven transport from horizontal mass flux measurements was greatest in the shrubland (15.0 g m(-2) d(-1)) followed by the grassland (1-5 g m(-2) d(-1)) and the forest sites (0.17 g m(-2) d(-1)). Annual projections accounting for longer-term site meteorology suggest that wind erosion exceeds water erosion at the shrubland by c. 33 times and by c. five times at the forest, but not the grassland site, where the high clay content of the soils contributed to greater amounts of water erosion: water erosion exceeded wind erosion by about three times. Horizontal transport by wind was greater than that by water for all three systems, overwhelmingly so in the shrubland (factor of c. 2200). Our results, which include some of the only wind erosion measurements to date for semi-arid grasslands and forests, provide a basis for hypothesizing trends in wind and water erosion among ecosystems, highlight the importance of wind erosion and transport in semi-arid ecosystems, and have implications for land surface geomorphology, contaminant transport, and ecosystem biogeochemistry. Copyright (C) 2003 John Wiley Sons, Ltd.