Almost no part of the world's oceans will be untouched by the influence of climate change.
That's one of the findings of a study released yesterday in the journal PLOS Biology.
"We are truly making a big mess out of the ocean with this climate change," said Camilo Mora, the University of Hawaii, Manoa, professor who led the research.
Mora led a group of 28 scientists who used output from the latest generation of climate models to calculate changes in acidity, temperature, oxygen and productivity for the world's oceans by 2100. They show that across the world's oceans, everything from food chains to fisheries will see influences of climate change.
The paper is divided into three main parts: climate change impacts on ocean chemistry, on ocean biology, and on human societies that rely on the ocean for various goods and services, Mora explained.
The analysis shows models projecting increases in acidity and temperature across the Earth's oceans. Such trends have already led to significant negative events in coral reefs, such as bleaching and death, and they could also affect yields in fisheries.
The only part of the ocean that sees increases in oxygen is near Antarctica, and the only areas that have productivity increases are near both poles, according to the research.
Yet even those seemingly positive changes may not be, explained study co-author Chih-Lin Wei, a postdoctoral fellow at the Memorial University of Newfoundland.
Stark choices needed now
"Invasive species have been immigrating to these areas due to changing ocean conditions and will threaten the local species and the humans who depend on them," Wei said.
The researchers also found, in their analysis of climate change influence on marine habitats, that changes in ocean biogeochemistry will lead to significant negative effects on species such as tuna, seals, whales and dolphins, and on krill, which is an important food source for many ocean animals.
While other researchers have made similar points using older data, this paper is new in using output from the latest set of climate models and scenarios from the Intergovernmental Panel on Climate Change, noted John Bruno, a biologist who researched climate change impacts on marine ecosystems at the University of North Carolina, Chapel Hill, and who reviewed the paper.
Bruno also appreciated how the researchers outlined the effect of future changes on various habitats, parts of the ocean like mangroves, sea mounts, vents and coral reefs.
The paper also highlights the stark choices humans have to make about taking action now to avoid extremely negative impacts of future climate change, Bruno said.
Sharp economic impacts from a changing sea
The third part of the paper demonstrates just how many people will be affected by such changes to the ocean. Under the business-as-usual scenario, more than 2 billion coastal people will see medium or high changes in ocean biogeochemistry in the coasts near them. Nearly half those people -- 870 million -- come from low-income countries.
If emissions are curbed, the number of people living in areas with significant ocean changes drops to 1.4 billion, with 470 million from low-income countries seeing impacts.
As Mora pointed out, people living near coasts rely on the ocean for jobs, cash and food. These were all taken into account in their analysis. "I wanted to highlight that we rely on goods and services that we take from nature," Mora said. "This is going to influence people for real."
Rashid Sumaila, director of the fisheries economics research unit at the University of British Columbia Fisheries Centre, called the study's findings "robust," writing in an email that the paper made a "good contribution."
Mora said that one of the original reasons he wanted to conduct the analysis was to see climate change's effects in the deep ocean, but that there are not yet enough data for them to have confidence of their projections of changes in that part of the ocean.
"The models are not doing as great of a job at predicting what is happening in the deep sea," he said.
Other co-authors of the paper called the findings "scary," saying even small changes in the ocean's temperature, oxygen and acidity could affect deep ocean communities.