Microbiotic crusts are found throughout the world, from the hottest deserts to polar regions. Most of these crusts are dominated by cyanobacteria, and also include lichens, mosses, green algae, microfungi, and bacteria. The crusts are critical components of these ecosystems, significantly modifying the surfaces on which they occur. In the cold deserts of the Colorado Plateau region (parts of Utah, Arizona, Colorado, and New Mexico), these crusts are extraordinarily well-developed, and may represent 70-80 percent of the living ground cover. Cyanobacteria, previously called blue-green algae, are the oldest form of life known. The earliest fossils found, called stromatolites and dating back more than 3.5 billion years, are extremely thick [...]
