Breached Boundaries: Ocean Acidification Surpasses Safe Limits
Last year ozone depletion, one of the nine planetary boundaries, remained within the safe operating level, with global concentration average put at 285 to 286 Dobson Units (DU), above the safe limit at 277 DU, a less than five percent reduction from the pre-industrial level of 290 DU.
The atmospheric aerosol loading, another planetary boundary, remained within a safe operating level, with an interhemispheric AOD difference of around 0.063, which is below the safe threshold of 0.10, a situation largely due to the falling aerosol emissions fall from Europe and North America over recent decades.
Ocean acidification also remained within the safe operating level, making it only the third boundary with the status.
But now, new assessments state that ocean acidification had in fact breached the planetary boundary, with 60 percent of the subsurface ocean water to the depth of 200 meters compromised, along with 40 percent of the surface water.
With ocean acidification joining seven other planetary boundaries that have been breached, the planet may find its systems pushed out of the stable, human-friendly state that has prevailed in the past eleven thousand years.
In 2023, fossil fuels constituted a large part of global energy consumption, with oil, coal, and natural gas forming over 82 percent of total energy supply, the issue contributing to more than 70 percent of global greenhouse gas emissions and nearly 90 percent of carbon dioxide emissions.
Between 1990 and 2020, 420 million hectares of forest were lost through deforestation, with wildfires one of the primary drivers of a process that led to the carbon dioxide emission equivalent to the annual emissions of 570 million car from forest loss.
Globally, 62 percent of land areas have been transformed largely from naturally vegetated area to urban, agriculture, and other human-modified landscapes, with land use change said to be responsible for about 3.1 gigatonnes of carbon dioxide equivalent in 2022, the sector accounting for about 19 percent of total global greenhouse gas emissions.
Ocean acidification comes from the absorption of carbon dioxide emissions from the burning of fossil fuels, deforestation, and land-use change, with experts putting the increase at 26 percent since pre-industrial times, a rate of change which is 10 times faster than at any time in the past fifty million years.
The ocean absorbs 30 percent of all carbon dioxide emissions and captures 90 percent of the excess heat from these emissions, but climate change could be accelerated in this process, since acidification could decrease the ocean’s ability to absorb heat and carbon dioxide.
The oceans provide habitats for around 230,000 known species, as well as countless others not known, but acidification could cause population declines in these life forms, which could weaken their resilience and adaptability to climate change.
The oceans allow for fisheries, tourism, and coastal economies, but ocean acidification could affect all of this, with estimated annual cost from mollusc loss put at $100 billion by 2100, which could make many to be at the mercy of the worst effects of climate change.
The oceans absorb a vast amount of solar radiation, and redistribute it around the globe, but acidification and heat distribution could create a feedback loop, because as the ocean warms, its ability to absorb carbon dioxide may decrease, leading to increased atmospheric carbon dioxide levels and further warming.
In other words, with ocean acidification joining the other six planetary boundaries that have crossed safe operating levels, the situation could become even more desperate in the coming years.
To solve the problem of ocean acidification, humans have to change, reduce the consumption of fossil fuel, transit to renewable energy, and cut down pollution from land based activities such as agricultural run-off and sewage.
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