a b s t r a c t
This article reviews current knowledge on cyanobacteria, the dominant primary producers, and other
microorganisms in arid desert environments. These microorganisms have developed an array of adaptations
to hot, arid climates with intense UV radiation, extreme diurnal temperature fluctuations, and
high soil salinity. Crust microorganisms positively contribute to their harsh ecosystems, by preventing
evapotranspiration, fixing nitrogen, and blocking solar radiation. In doing so, desert crust prevents soil
erosion and facilitates the establishment of plant species. However, like aquatic cyanobacteria, desert
cyanobacteria have the potential to produce toxins linked to human and animal illness. Furthermore, the
impact of terrestrial cyanobacterial toxins on human health in desert regions is poorly understood. A
largely ignored, but potentially important human exposure route for cyanotoxins in desert environments
is through the inhalation of desert crusts during dust storms and anthropogenic activity. Future work in
this field should include the characterization of toxins produced in desert regions as well as the presence
of toxins in clinical and environmental materials.