Last week a group of 155 scientists signed the 'Monaco Declaration' of ocean acidification and presented one of the most succinct and compelling arguments of why we need to begin curbing carbon dioxide emissions - immediately.
Ocean acidification is a second global impact of rising atmospheric CO2 concentrations (in addition to climate change). Approximately one third of all anthropogenic (man-made) CO2 emissions is absorbed by the oceans. This CO2 immediately becomes an acid in water, and increases the acidity of the oceans. Since the industrial revolution, average acidity of ocean water has increased by 30%. This change in ocean chemistry makes it more difficult for shelled organisms (e.g., crabs, lobsters, oysters, sea urchins, corals and some phytoplankton) to build their shells. If emissions continue on a business as usual trajectory, ocean acidity will approach triple the pre-industrial levels by the end of the century. At these levels, many species or organisms - particularly shelled organisms - will struggle to survive.
The argument in the Monaco Statement is built on six undisputed observations and one highly likely prediction (#4):
1. Ocean acidification is underway.
2. Ocean acidification is already detectable.
3. Ocean acidification is accelerating and severe damages are imminent.
4. Ocean acidification will have socioeconomic impacts.
5. Ocean acidification is rapid, but recovery will be slow.
6. Ocean acidification can be controlled only by limiting future atmospheric CO2 levels.
7. There is still time to act if serious and sustained actions are initiated without further delay.
Two points are worth emphasizing: 'severe damages are imminent' and 'recovery will be slow'.
At current CO2 emissions rates, large regions of the polar oceans will become corrosive to shells of key organisms (base of the food chain) in the next 20-30 years and they will no longer be able to survive in these regions. When atmospheric CO2 concentrations reach double the pre-industrial level (560 ppm) - which could very well happen by mid-century - the erosion of coral reefs will out-pace their growth and they will likely go extinct globally (or certainly in the reef-building form that we know them). This prediction is based on empirical observations of coral calcification rates. The timing of the prediction might vary by decades but the phenomenon and outcome is not in dispute. Tipping points for other calcifying organisms exist but they remain unknown.
If carbon emissions are not stabilized during this century, it will require thousands of years for the oceans' chemistry to return to current conditions. And it will be hundreds of thousands to millions of years for coral reefs to return.
The phenomenon of ocean acidification is simple. It is undeniably caused by human activities, and there is relatively little variation in model predictions compared to climate change. The Monaco Declaration reveals a growing concern and strong consensus among ocean experts: we are now at the cusp of severe and essentially permanent damage to marine ecosystems and we must act now.