Step 1 : Introduction to the question "Trees develop crown shyness to avoid what?"
...First documented in scientific literature in the 1920s, crown shyness is a tree’s way of keeping itself and other trees healthy. You can see it by looking up from the base of the tree — the leafy treetops fall short of touching, leaving gaps in the canopy. Trees developed this behavior to avoid spreading diseases, bugs, and parasitic plants, as well as to continue thriving as a species. Crown shyness has other advantages, too, like letting light in for photosynthesis.