While constant change characterises ecology, subtidal ecologists seem set to take a deep dive in to the biological processes that accelerate and compensate for environmental change. Similar to the technological and collaborative progress that benefited the present generation of authors, continuing progress may assist future generations of subtidal ecologists to figure out why kelp forests are characterised by global mosaics of long-term loss, gain and stasis. Where and how might kelp decline or flourish or simply persist future ocean change? Our review takes a biogeographic perspective to synthesise ecological patterns and the processes that create them. On this basis, we consider the modification of ecological processes by oceans undergoing physical and chemical change and, as a result, consider their future ecology. We find that future oceans will make life beyond the capacity of kelp to exist on many coasts, but not all coasts will be beyond the capacity of a kelp’s life. Consequently, this review provides a sign post for future research into the future decline or persistence or even increase of kelp forests.