Our world’s biodiversity has long been under pressure, in most cases due to human activities. The conservation of biodiversity requires more than the protection of a nature reserve. It calls for knowledge of and insights in the many interactions that occur between the different species that are present. For a long time ecological research focused on negative interactions such as competition and predator-prey relations. However, in recent decades focus shifted towards the role of positive interactions on community structure. When different species facilitate one-another, for example by providing shade, shelter or structure, a domino-effect can occur. In so-called facilitation cascades a primary habitat-forming species facilitates a secondary habitat-former, which on its turn promotes biodiversity and species abundance. These positive interactions are sensitive to variation in traits and function of habitat-forming species. It turns out that oysters and mussels – seemingly similar species – facilitate the development of different macroalgae and associated species due to their different ecological function, and the morphology of macroalgae affects the species that are being facilitated. Furthermore, a single primary habitat-former can generate multiple facilitation cascades that positively effect biodiversity on both long and short spatial scales. This strongly connects different habitats via a network of positive interactions. These complex networks highlight the importance of cross-habitat management initiatives that aim to promote biodiversity by conserving habitat-forming species and their positive interactions.