INFORMS ENRE Section
INFORMS has a Section on Energy, Natural Resources, and the Environment. The focus seems to be about application of OR techniques to these fields. There does not seem to be a slant in the direction of sustainability, though it is likely that some digging would reveal some members doing that kind of work. It is just about OR applied to problems in these areas.
According to their site, they have “two strong and active groups: Forestry and Energy”. The site has a decent amount of information including the Section’s presentations at the recent major conferences such as INFORMS 2006. Following up on those lists, as well as looking into the research of the Section officers (also listed on the site) would reveal more.