Given the nature (pun possibly intended) of the book, the author could say everyone who can read and lives is an appropriate target audience. But that is possibly a tad greedy without further qualification. :-)
The Preface available in the Preview gives a more in-depth motivation. But overall, the intent is to share what I have learnt from Nature, in the form of a pragmatic philosophy. Teachings that cannot be applied are pointless, after all.
A more important goal is one of guiding readers towards self-discovery and self-reflection. I am a big believer in the ability of self-reflection to bring about major changes in attitudes of living, sometimes nearly instantly. I also believe that self-reflection is enhanced by having examples of such reflection — examples this book provides.
I invite the readers to learn to interpret elements of Nature, both globally, but also rather more usefully, specifically to the reader's state of being at a point in time.
Finally, you don't have to be an adventurer going out to remote wilderness to get in touch with Nature, by any means. Only a little quietude in a natural setting is needed to quickly connect. But, the intent to connect must be deliberate.