One important topic is the psychology of nature.  
There may be many interesting findings concerning
nature and human judgment/feelings.  Exposure to
nature may be beneficial in a few ways. For
example, one of the possible benefits of exposure
to nature is that it may increase happiness. This
page contains articles with research findings
concerning nature.
Is Feeling Connected to Nature Asssociated with Life Satisfaction?
Can a Walk in a Park Increase Happiness?
Can Exposure to Nature Influence Our Aspirations?