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Biological Soil Crusts and You!

Biological Soil Crusts and You!

Posted in: Education, Nature on January 26, 2024.

Strange, Dark Lumps in the Sand

If you’ve ever been hiking in the deserts of Southern Utah, then you’ve probably come across strange, blackish bumps in the sand, about an inch or two tall. And you may have wondered to yourself, “What the heck are these things?” Well we have the answers! Those are biological soil crusts. And they are complex colonies of bacteria, fungi, algae, and lichens. You can find biological soil crusts here in Capitol Reef National Park, in the high deserts of Southern Utah, and in arid and semi-arid regions everywhere across the world. And it probably won’t surprise you to learn that they play a vital role in these environments.

Dark bumps in the desert sand

Photo by Nihonjoe via Wikimedia Commons

What Do They Do?

Biological soil crusts are very important for the health of the desert ecosystem. The help fix atmospheric carbon and nitrogen, providing essential nutrients for the sparse vegetation that does grow here. They also reduce soil erosion, and collect water, preventing the sands from being washed away during rainstorms. Most of these colonies of bacteria have large populations of cyanobacteria, which are actually capable of photosynthesis. And because they absorb some of the sun’s rays, the desert sands are less reflective in areas with established soil crusts. Which is good news for your eyeballs. (If you’re curious, the measure of reflective light off of a surface is call albedo.)

How Are They Made?

Biological soil crust begins to form when fungi spores colonize the area between desert plants. Once the fungi has stabilized, cyanobacteria and other bacteria, such as bryophytes, congregate around the fungi structures. Eventually, lichens and algae join the party. The whole process takes a long time to complete. Depending on the amount of water available in the region, it can literally thousands of years for mature soil crust to develop.

Biological Soil Crust covering the desert sands

Photo by Nihonjoe via Wikimedia Commons

Look. But Don’t Touch.

Biological soil crusts are extremely fragile. (Which, considering how long they take to form, is completely understandable.) Crushing and tearing soil crusts can result in widespread colony collapse. You may permanently destroy the soil crust, or at least, impact the area for decades, if you step on it. This in turn leads to substantial soil erosion – negatively impacting desert plant life and, in turn, the animal life which depends on the plants.

Everyone who visits the national parks of Southern Utah falls in love with the area. Help do your part to keep this place as beautiful as it is. One way to do that, is to not damage the soil crusts that are so important to the life of our deserts. So when you’re hiking or riding your ATV in Southern Utah, think of the little colonies all around you, and avoid any distribution of the biological soil crusts. Stay on the designated trails and roads, or if you’re hiking where there are no trails, walk in sandy washes or on bare rock so as not to destroy the little guys. They’re our friends, after all.

You can learn more about biological soil crusts here on Wikipedia and here on the National Parks Service website.

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