Moss on Shingle Roofing

I live in the southeast and have noticed fairly new roofs that are starting to mildue.  Is this a geographical condition or the type of shingle being used?

It is a location problem but not just there.  It can be solved using shingle shield { roof cleaner} I believe it can also be used to prevent moss build up, algae problem can also be the product of poor roof ventilation, also if there are trees growing toward the roof causing there to be a shadow on the roof ...cut its limbs!!!