Look closely -- what can you learn?Photo: Steve WallThe Center for Ecoliteracy has worked for more than 15 years to make schools greener. During the course of our work, collaborating with thousands of educators and change agents, we've learned invaluable lessons about how to tackle the challenge of changing often-entrenched systems. We're pleased to share those lessons here, to help people who want to make change anywhere.  The first guiding principle of our work at the Center for Ecoliteracy is "nature is our teacher." Taking nature as our teacher requires thinking in terms of systems, one of nature's basic patterns. …