As a naturalist who travels, I often find myself examining things that might be often overlooked, particularly in places where many people might not give them much thought. Such as case over the past few years has been trees in cities. I began to take greater notice of them a few years ago on a business trip to the U.S. city of Indianapolis, Indiana; an interest that received a significant boost when I discovered that in Nürnberg, Germany all the trees are given identifying numbers to make their care more efficient and effective.