Sounds like danger’s playground! Crawlspaces are wonderlands for all the things we hate like mold and pests. Since most people like cold, time, damp, and dark spaces, these problems have time to get nice and comfortable.
At best this environment is perfect for wood decay. This could simply mean expensive repairs. But likely, other issues will arise. Mold might be noticed by those with allergic reactions including running nose or even fever.
Termites and ants might find it an ideal location as well. Both can cause structural damage to a home. Of course, if we ignore the early signs of pests, what do we do? We kill them with pesticides. These pesticides themselves can cause problems for us, at least if someone goes into the crawl space for an inspection.
Because moisture creates such an inviting environment, many homes have crawlspaces vented. Although this helps with the moisture, many are now concerned that this is becoming an issue for heat loss and energy conservation.