The projected increase in the frequency, severity, duration and areal extent of MHWs threaten many marine species and ecosystems. These MHWs may exceed the thermal limits of species, and they may occur too frequently for the species to acclimate or for populations to recover. The majority of the world's coral reefs are projected to decline and begin eroding due to more frequent bleaching-level MHWs if the world warms by more than 1.5℃. Recent research suggests possible shifts to more heat-tolerant coral communities but at the expense of species and habitat diversity. Other systems, including kelp forests, are most threatened near the edges of their ranges, although more research is needed into the effect of re-occurring MHWs on kelp forests and other vulnerable systems.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report