Desert Magic: Why You Should Care About Cryptobiotic Soil

Covering more than a tenth of the Earth’s landmass, biological soil crusts play a crucial role in maintaining the health and stability of fragile desert ecosystems. Composed of a delicate web of cyanobacteria, lichens, and mosses, these structures are among the oldest living things found on Earth, but their very existence is threatened. As scientists are only beginning to understand their importance, climate change and increased tourist traffic – especially in popular national parks such as Moab or Joshua Tree – are putting biocrusts at risk.

The beautiful reds, ochre and browns of the desert landscapes are largely due to the biocrust communities that form their foundations. Thanks to the secretion of a glue-like substance called exopolysaccharide, cyanobacteria bind the desert surface, allowing it to become a habitat for vibrant plant and animal life. Due to extreme temperature changes typical of the desert, the frequent freezing and thawing action causes the biocrusts to form tiny towers and pyramids that are then colonized by communities of hairy mosses, rugged lichens and microfungi.

This breathing, living layer of interconnected organisms has an uncanny moisture-holding capability. It remains dormant when dry but springs back to life the moment that rain touches its surface. It also prevents the violent desert downpours from eroding the land. Biocrusts slow water runoff and allow life-giving moisture to penetrate the deeper parts of the soil where it nourishes vascular plants such as grasses, flowers and cacti.

In addition to binding the desert’s surface, cryptobiotic soils play a crucial role in preventing dust emissions and storms – a phenomenon that has undergone a dramatic increase in the last few years. Excessive dust release not only deteriorates air quality but also accelerates glacier melting and reduces river flows, impacting ecosystems far beyond the arid desert landscapes.

Even after recently beginning to study and comprehend the importance of cryptobiotic soils, scientists are sure of one thing: despite their extreme resilience to temperature changes, long-term drought, and even UV radiation, biocrusts are actually very fragile and easily disturbed by human activities. Off-trail hiking and vehicle traffic collapse the airy structure of the cryptobiotic soil, causing damage that takes years to rebuild. In addition, once disturbed, the cryptobiotic layer loses its water-retaining capabilities. It is then not only vulnerable to further erosion, but also cannot transport moisture and nutrients into the deeper layers of soil. Without a thriving cryptobiotic community at its base, the desert begins to die.

“Don’t bust the crust” is a catchphrase inviting all visitors to the desert to become aware of the complex microcosmos at risk of perishing under our feet. Staying on existing trails is of paramount importance for protecting the biological crusts that literally hold together some of the most beautiful, arid landscapes of the US and the world.