Rising CO2 levels may affect most coral reefs and their populations by 2050

Indicator mapping predicts Oceanian, Southeast Asian populations particularly under threat by 2050

This figure depicts country-level dependence on coral reef ecosystem services and future combined normalized scores (2-20) for ocean acidification and thermal stress. The darker brown swaths indicate higher human dependence on coral reefs. Areas with more red indicate greater future stress due to the combined effects of climate change and ocean acidification. Credit: Pendleton et al (2016)
This figure depicts country-level dependence on coral reef ecosystem services and future combined normalized scores (2-20) for ocean acidification and thermal stress. The darker brown swaths indicate higher human dependence on coral reefs. Areas with more red indicate greater future stress due to the combined effects of climate change and ocean acidification.
Credit: Pendleton et al (2016)

Nov. 10, 2016 – Rising CO2 levels may affect most of the world’s coral reefs and the populations which depend on them by 2050, according to a study published November 9, 2016 in the open-access journal PLOS ONE by Linwood Pendleton and Adrien Comte from the Université de Bretagne Occidentale, France, and colleagues.

The effects of rising atmospheric carbon dioxide (CO2) levels include ocean acidification and rising sea surface temperatures, which put shallow warm-water coral reefs at risk. This could also affect the people who depend on the reefs for their livelihoods for fishing, tourism, or as natural barriers that protect shorelines.

The authors of the present study used an indicator approach to identify countries where coral reef-dependent people were most likely to be affected by 2050. They scored and mapped two indicators of CO2-driven coral reef stress, ocean acidification and rising sea surface temperatures, along with two indicators of human dependence on coral reefs. Combining these maps of indicator scores allowed the researchers to identify regions where humans were most likely to be affected by increasing atmospheric CO2 levels.

The authors found that most of the world’s coral reefs were likely to be affected by either warmer seas or more acidic oceans. They predicted that countries in Oceania would be amongst the first affected by CO2-driven coral reef stress, followed by Southeast Asian countries in the Coral Triangle such as Indonesia, which are highly dependent on coral reefs. Countries predicted to be most likely to experience severe ocean acidification are generally different from those predicted to experience the earliest onset of coral bleaching, with acidification projected to be worse for countries at the upper and lower latitudinal bounds of coral reef distribution such as Baja California (Mexico), Japan, China, and southern Australia.

Unfortunately, many of the countries that are most dependent upon coral reefs are also the countries for which data are least robust, and the authors note that international and regional efforts will be needed to overcome obstacles to obtaining good data globally.

“Our study finds areas of high human dependence on coral reefs also facing high combined threats from future stresses due to climate change (bleaching) and ocean acidification. By 2050, coastal communities in Western Mexico, Micronesia, Indonesia, parts of Australia and Southeast Asia will bear the brunt of damage to coral reefs caused by rising temperatures and ocean acidification,” said Linwood Pendleton, the study’s lead author, a senior scholar at Duke University’s Nicholas Institute for Environmental Policy Solutions and an International Chair of Excellence at the European Institute of Marine Studies.

Freely available paper: http://dx.plos.org/10.1371/journal.pone.0164699

Citation: Pendleton L, Comte A, Langdon C, Ekstrom JA, Cooley SR, Suatoni L, et al. (2016) Coral Reefs and People in a High-CO2 World: Where Can Science Make a Difference to People? PLoS ONE 11(11): e0164699. doi:10.1371/journal.pone.0164699