Ocean heatwaves are more frequent and threaten biodiversity

Marine heatwaves are increasing in frequency, with 54% more heatwave days per year from 1987-2016, than from 1925-1954, suggests a paper published online this week in Nature Climate Change. The study finds that these events vary in their physical manifestations, yet all affect key species and ecosystem structure and functioning.

Regional case studies have documented how marine heatwaves (MHWs) can alter the structure and function of entire ecosystems by causing widespread mortality, species range shifts and community reconfiguration. By impacting ecosystem goods and services, such as fisheries landings and biogeochemical processes, MHWs can also have major socioeconomic and political ramifications.

Dan Smale and colleagues used the existing MHW framework to quantify trends and attributes of MHWs across all ocean basins, and examined their biological impacts from species to ecosystems. They found that multiple regions within the Pacific, Atlantic, and Indian Oceans are particularly vulnerable to MHW intensification, due to the co-existence of high levels of biodiversity, a prevalence of species found at their thermal limit, or concurrent non-climate human impacts. Although the MHWs varied considerably, all were harmful across a range of biological processes and organisms, including critical species like corals, seagrasses and kelps.

The authors conclude that climate change will continue to increase the frequency of marine heatwaves and the associated impacts on marine biology could have broad reaching effects on ecosystems and the services they provide.