Climate change and ocean acidification – a looming crisis for Europe’s cetaceans

Climate-related changes, including increased sea surface temperature (SST), decreasing ice cover, rising sea levels and changes in ocean circulation, salinity, rainfall patterns, storm frequency, wind speed, wave conditions and climate patterns are all affecting cetaceans (Learmonth et al., 2006; Silber et al., 2016). Additionally, an increase in the amount of carbon dioxide (CO2) being absorbed by seawater is leading to ocean acidification, which – in turn – amplifies the adverse effects of global warming (Pace et al., 2015; IPCC, 2018).

Understanding the mechanisms through which climate change impacts any given species is a challenge, and scientists are increasingly focused on trying to predict consequences (Simmonds, 2016). The International Whaling Commission (IWC) has held a series of workshops about climate change and has highlighted the need to understand the relationship between cetacean distribution and measurable climatic indices such as SST (IWC, 2010).

The impacts of climate change on cetaceans can be direct, such as thermal stress, or indirect, such as changes in prey availability (Learmonth et al., 2006). Effects can lead to changes in distribution, abundance and migration patterns, the presence of competitors and/or predators, community structure, timing of breeding, reproductive success and survival. Other potential outcomes of climate change could be more dramatic, such as the exacerbation of epizootics (Simmonds, 2016). The incidence of harmful algal blooms may also increase as a result of climate change. The Scientific Committee of the IWC has recently looked at this topic and concluded that the toxins from the blooms have resulted in an increasing risk to cetacean health at the individual and population levels (IWC, 2018).

Human activities have caused approximately 1.0oC of global warming above pre-industrial levels (IPCC, 2018) and it is estimated that global warming will reach 1.5oC between 2030 and 2052. In the last 50 years the world’s oceans have absorbed more than 90% of the excess heat in the climate system (IPCC, 2019). The rate of ocean warming has more than doubled since 1993 and marine heatwaves have become common and more intense.

See link for full report: Report_UNDER-PRESSURE_need-to-protect-whales-and-dolphins-in-European-waters_OC.pdf (

Nunny L. & Simmonds M. P., 2021. The need to protect whales and dolphins in European waters. OceanCare Under Pressure. Report.

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