Bryozoan constructions have been present in all major climatic zones of marine ecosystems for the past 450 million years, since the Early Ordovician. Some fossil species possessed large bioconstructional colonies that would have provided habitats for other marine animals and plants, just as similar colonies do at the present day. Today, biogenic calcareous structures vary greatly in size, ranging from a few centimetres to many kilometres, and in complexity, forming composite structures that are distributed globally. Despite the role of bioconstructional bryozoan species in promoting marine biodiversity worldwide, they have been excluded from several protection strategies. Information emerging from the literature provides only a very incomplete picture of the role of bryozoans as bioconstructors at the global level. The ability of bryozoans to form long-lasting carbonate structures makes them important carbonate producers, with a significant role in the carbon cycle. Bryozoan reefs are facing the challenges of climate change, which will be detrimental for some species and their associated biota. Better knowledge of the contribution of bryozoans to the carbon stock and the ecosystem services they provide will be of great importance to ensure their protection and to understand their potential in adaptation strategies under future ocean scenarios. © Springer Nature Switzerland AG 2020. All rights reserved.