Because of the high humidity level in a
dirt crawl space,
cool surfaces such as the earth at 55 degrees, concrete and metal
surfaces will sweat with water vapor condensing out of the air. This
causes rot, smells, and is a water source for critters. Critters- Bugs,
Rodents and MORE BUGS.
Dirt crawl spaces are great places to live, thrive and reproduce if
you're a bug. There is an even temperature, moisture, damp wood and
shelter. Spiders, beetles, centipedes, termites, and all kinds of other
insects are found in dirt crawlspaces .
Animals such as mice (dead and alive) are commonly found in dirt crawl
spaces. In some cases, even rats, snakes and small animals have been
found.

Structural Damage in places like Atlanta and surrounding areas in GA
Moisture is the prime factor that causes structural
damage. Over time, rot and decay form a moist environment damaging wood
framing and steel structural members.

Mold spores, the seeds of mold, are in the air everywhere. All they
need to grow is organic material such as wood, the right temperature
range, and moisture. Of these, the only one that can be controlled is
moisture.
Dirt crawl spaces have the high humidity levels necessary for mold
growth. Humidity levels from 50% to 90% are easily found in dirt crawl
spaces that have never flooded. Mold can grow on dirt, insulation,
framing and even under your carpet on the first floor. Mold destroys
organic materials as it feeds on them. Many people are sensitive to the
millions of floating airborne spores mold reproduces, causing allergic
reactions, illness and asthma. Spores can be dormant for many years,
waiting for the right conditions to grow. Some molds produce
mycotoxins, such as the black mold Stachbotrys. There has been
considerable recent documentation on the effects of mold, and toxic
mold.
Dr. Harriet Burge, an expert in airborne diseases at the Harvard School
of Public Health says, "Mold in houses is not a good thing. It could
lead to asthma. Houses with mold are damp, and have dust mites and
other things in them that can cause illness, especially in children."
Don't panic; there is a solution that will stop your crawl space from being a hospitable environment for mold. Mold will not grow when the humidity levels are reduced below 40%.