•The two-way dependency of streams and their riparian forests is reviewed.•We focus on biodiversity and ecosystem functions, including microbial processes.•Land use and climate change effects on riparian and stream ecosystems are discussed.•Potential management and protection practices are overviewed.•Future research questions are drawn together. In this review, we draw together the research on the two-way connection of streams and their riparian forests of the boreal zone from ecological points of view. Although the knowledge about stream-riparian interactions has increased considerably recently, in practice, riparian zones are still mainly seen as buffers for nutrient and sediment loading. However, recent research has shown that riparian forests disproportionately foster regional biodiversity and maintain stream ecosystem functions and diversity. On the other hand, streams contribute to riparian diversity and ecosystem functions. Microbes are key drivers of global biochemical cycles, and they also interact with plants and animals. The knowledge on microbial communities and understanding of processes they drive has considerably increased due to recent development in microbial profiling methods. However, microbes have been largely neglected in former reviews. Thus, this overview has a special focus on the role of microorganisms in controlling stream-riparian interaction. We also review the land-use pressures that are threatening biodiversity and ecosystem processes of riparian zones in forested landscapes. In addition, we review the possible effects of climate change on stream-riparian interactions. Finally, we outline the research gaps that call for future research.