The impact of human activity on the Mojave National Preserve


Biological soil crusts are important parts of the desert ecosystem. The biological soil crusts cover the areas not covered by green plants. Cyanobacteria and other organisms live in these crusts and are instrumental in minimizing erosion, increasing water retention, and improving the health of the soil. Cyanobacteria help to prevent erosion by secreting a sticky substance that acts to bond particles in place. The organisms living in the biological crust are helpful increasing water retention because when it does rain, these organisms are able to absorb up to ten times their volume in water. Perhaps most importantly, these organisms work to fix nitrogen and produce organic matter. These both make soil healthier; consequently, it is easier for plants to grow in the already harsh conditions of the desert.

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Humans affect this process in several ways. When walking through the desert, footprints compress the biological crusts, which is concentrated in the top eight of the soil. Also, when farmers have livestock walk through the Mojave Desert, it condenses the important biological crusts which are instrumental in the overall health of the ecosystem. When the crusts are crushed, they produce significantly less nitrogen and require nearly twenty years to recover under conditions of high rainfall and up to 250 years of recovery in conditions of sparse rainfall.