The blue growth agenda has spurred an accelerating exploitation and continued development of the coastal and marine environment. This is also driven by the increasing need to generate renewable energy. In most cases, this has resulted in a large number of man-made structures (MMSs) across several soft sediment environments. The nature of these structures ranges from oil and gas installations to harbour walls, anchored buoys, pipelines and offshore wind farms. These structures host fouling communities that are often new to offshore regions, potentially serving as stepping stones for range-expanding (non-indigenous) species and providing habitat and shelter for a variety of marine species. The altered local biodiversity also affects biological and biogeochemical processes from the water column to the seafloor, either directly (e.g. scouring, organic matter export from piles) or indirectly (e.g. closure or displacement of fisheries) and, hence, ecosystem functioning at various spatial and temporal scales. A proper understanding of the effects of artificial hard substrate and the consequences of its removal (e.g. through decommissioning) to marine biodiversity has yet to develop to maturity. This themed article set contributes to the scientific knowledge base on the impacts of MMSs on marine ecosystems with the specific aim to fertilize and facilitate an evidence-based debate over decommissioning. This discussion will become ever more vital to inform marine spatial planning and future policy decisions on the use and protection of marine resources.