Cryptobiotic Soil Crusts

Take a walk. Look at the ground. What do you see? You might see shrubs, cactus, grass, or plants.

You may see a lizard sitting in the sun. Watch where you step. Some plants and animals are fragile.

Look between the plants and rocks. Can you see patches of black, knobby dirt (Photo on the right)? This is called cryptobiotic soil.


What Is In The Name?

Look more closely. This soil is actually alive. It is made of many tiny living things.

Cryptobiotic crusts are found in dry places all over the world. Much of the ground in the southwestern United States is covered with this soil crust.

This crust is filled with cyanobacteria. Lichens, mosses, algae, microfungi, and bacteria are other life in the soil crust. These living clumps help to hold things together. The crusts are like a woven mat.

Ancient cyanobacteria fossils are found in many places. Cyanobacteria have been on the earth for billions of years. They helped change the earth's air from carbon dioxide to oxygen. Most of today's plants and animals need oxygen to live.

Cyanobacteria occur alone or in groups. The groups are held together like threads. When water is available, these threads expand. The soil crusts swell and move. This makes the ground bumpy.

Why Are These Soil Crusts Important?

Cryptobiotic soil crusts are important to nature. They help stablize the soil. They stop wind and water erosion. They also help feed and water the soil.

Threats To Soil Crusts And Their Environment

Cryptobiotic crusts are easily damaged. A footprint can kill the soil (Notice trails in photo to the right). Bikes leave long, winding strips of damage.

Crusts need sunlight to live. They die when they are buried. Dead areas may become sand dunes.

When the crust dies, wind and water carry away the soil.

It's difficult for cryptobiotic soil to recover. It can take five to seven years to regenerate. It may take 50 to 250 years to recover.

What Can You Do?

A misplaced footstep can turn crust to dust.

Look for cryptobiotic soil. Stay on trails and bike paths. Preserve nature.

More Information


Note: All photographs taken with a digital camera in Arizona and Utah.
Developed by Annette Lamb and Larry Johnson, 04/02.