Switching to paper bags instead of plastic bags will result in increased CO2 emissions. The oceans act as a sponge, taking up CO2 from the atmosphere which dissolves and forms an acid in the seawater.
According to a report by the Royal Society of Great Britain, sea creatures such as corals, shell fish, sea urchins and star fish are likely to suffer the most because higher levels of acidity makes it difficult for them to form and maintain their hard calcium carbonate skeletons and shells. For example, even under the 'low' predictions for future carbon dioxide emissions into the atmosphere, the combined effects of climate change and ocean acidification mean that corals could be rare on tropical and subtropical reefs, such as the Great Barrier Reef, by 2050. This will have major ramifications for hundreds of thousands of other species that dwell in the reefs as well as for the people that depend upon them, both for food and to help to protect coastal areas from, for example, tsunamis.
The report says that changes in ocean chemistry, caused by ocean acidification, means that we can predict that some creatures in the Antarctic Ocean will be among the first to be affected. For example, some types of plankton a major source of food for fish and other animals may be unable to make their calcium carbonate shells by 2100. This may have significant consequences for entire food webs in the region, although the overall impact of this is unclear.
Higher concentrations of carbon dioxide may also make it harder for some larger marine animals to obtain oxygen from seawater. For example, squid are particularly sensitive because they move by jet propulsion this is very energy-demanding and requires a good supply of oxygen.
The London Times reported as follows on the Royal Society’s findings:
[Dr. Hall-Spencer of the University of Plymouth, who led the Royal Society study, stated:] "Our observations verify concerns, based on laboratory experiments and model predictions, that marine food webs will be severely disrupted and major ecological tipping-points are likely if human CO2 emissions continue unabated."
This appraisal of life in a more acidic ocean was if anything conservative, Dr Hall-Spencer said, because it mimicked future ecosystems only partially.
The acidity around carbon dioxide vents can be reduced by rough conditions, which dilute the water - something that would not happen if the whole ocean was highly acidic.
The researchers also noted that while fish continued to swim through more acidic waters, they avoided breeding or spawning in them. “That isn't a problem at the moment, as they can go elsewhere,” Dr Hall-Spencer said. “But in a more acidic ocean there will be no escape.”
Global warming will also have an independent impact on sea life, by raising ocean temperatures.
When considering whether to ban plastic bags in favor of paper bags, the impact of greater CO2 emissions on the oceans must not be disregarded.
Click here for a BBC article about the huge destruction of coral reefs caused by global warming, and the devastating effect on marine ecosystems.