Conservation and development projects typically involve collaboration with local communities. It has been suggested that these collaborations should include the co-production of knowledge (e.g. Pohl et al., 2010; Wyborn, 2015; Nel et al., 2016), in which local communities work with researchers to produce new knowledge. Co-production is, however, expensive and we suggest here that co-assessment of existing knowledge is more cost-effective. We suggest the following three stages of using knowledge: collation, co-assessment, and then (rarely) co-production. We agree that other ways of knowing—including local, experience-based, and indigenous knowledges, as well as incorporating local values—have an important role in solving environmental problems (Collins & Evans, 2007; Sutherland et al., 2014), but we question whether it is effective to generate new knowledge with individual communities.