A variety of disciplines examine human-environment interactions, identifying factors that affect environmental outcomes important for human well-being. A central challenge for these disciplines is integrating an ever-increasing number of findings into a coherent body of theory. Without a repository for this theory, researchers cannot adequately leverage this knowledge to guide future empirical work. Comparability across field sites, study areas and scientific fields is hampered, as is the progress of sustainability science. To address this challenge we constructed the first repository of theoretical statements linking social and ecological variables to environmental outcomes. Stored in a relational database that is accessible via a website, this repository includes systematically formalized theories produced from researchers studying resilience, environmental conservation, common-pool resource governance, environmental and resource economics and political ecology. Theories are explicitly linked together in the database to form the first coherent expression of the types of human-environment interactions that affect outcomes for natural resources and, by extension, the people who use them. Analysis of this repository shows that a variety of types of theories exist, from the simple to the complex, and that theories tend to thematically cluster by scientific field, although the theories of every field were related in at least some way to theories from other fields. Thus there is much potential for increased interaction across these fields, hopefully with the help of resources such as this repository. The theories and variables employed to express their arguments are publicly viewable in a wiki-like format, as a resource for the scientific community.