Why does nature start and end Of Mice and Men?

It is an interesting proposition to suggest that there is
a natural bookend to Steinbeck's work.  Indeed, the opening and ending in the Salinas
Valley represents a couple of elements here.  The first is that it is the starting point
for the reader into the relationship between George and Lennie.  It is also the ending
point for George and Lennie.  In presenting their friendship in this manner, Steinbeck
might be trying to suggest that there is a natural ebb and flow to human friendships,
and this cyclical nature is seen here.  The friendship between George and Lennie has
endured so much that it has to end where it started, at least in the reader's mind.  The
tranquility and scenic beauty of the setting to open the novella is present at its end,
where so much to disrupt and cause chaos has been present. At the same time, the natural
elements might be to suggest that while friendships between human beings are fleeting
and transitory, the natural world is continuous.  It will not change, and while there
may be much in way of change, evolution, and alteration between human beings, the world
of nature stays the same.  This is brought out in the ending of Steinbeck's
work.