Evidences suggest that due to repeated leaching from soil, glaciations, floods, rivers changing course, all over a period of time, iodine deficiency will occur in most ecosystems, in the absence of intervention, because Iodine Deficiency ultimately leads to iodine deficiency disorders in human beings. The following chart illustrates this:

It is interesting to note that deforestation and felling of trees also contribute in escalating this problem over a period of time.

This knowledge was apparently present in ancient communities in India. Even today some ethnic communities (tribals of Jharkhand, Bihar, Orissa, Madhya Pradesh, Chhatisgarh etc.) even today worship trees. So much so that they have one of the largest community festivals, "Karam parv", when the tree is worshipped.