A landscape with no air flow is one where molds will thrive. Molds grow best in conditions with poor air circulation. If your own yards are over-grown and choked for lack of fresh air, then get out the pruning saw and start thinning them out. Clean, fresh air, free to move about, equals less mold and fewer mold spores. Sunlight and Molds Bright light and fresh air are the enemies of mold.
Many landscapes have huge trees overhead that let in little light.
Consider hiring a tree trimmer to thin out some of the branches overhead. Open the trees up so that the sunlight can come through. Perhaps it would be a good idea to actually remove a tree or two if they're growing too close. When planting any new tree, consider the shade that it will cast when it is full-grown. Certain trees always develop very thick canopies while others will be light and airy.