Ocean Acidification
Ocean acidification is the phenomenon of decreasing pH (increasing acidity) in ocean water due to the absorption of atmospheric CO2. This process harms calcifying organisms and reduces the ocean's efficiency to act as a carbon sink.
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Our oceans absorb CO2 from the atmosphere, but this results in a chemical change in sea water. The rapid increase in CO2 levels since industrialization has led to our oceans becoming more acidic, causing biodiversity loss and the degradation of delicate ecosystems and coral reefs. According to the current definition of the PB, ocean acidification is just within the Safe Operating Space (2.80), but it is close to crossing the safe boundary. Several new studies suggest that even these current conditions may be problematic for multiple marine organisms, suggesting a need for re-evaluating the safe boundary.
Latest News On Ocean Acidification
Impact
Crossing the safe boundary for Ocean Acidification has multiple impacts:
Corals struggle to build their skeletons, weakening reef structures.
Mollusks and other shellfish have difficulty forming shells impacting their survival and growth.
Some organisms (pteropods) at high latitudes have already damaged shells.
The availability of calcifying organisms changes, disrupting marine food webs and affecting species that rely on them for food.
Coral reefs, which are biodiversity hotspots, suffer, leading to the loss of habitat for many marine species.
Changes in carbonate chemistry reduce the ocean's capacity to sequester carbon, weakening its ability to mitigate global warming.
At low latitudes, where the aragonite saturation state is still relatively high, the absolute rate of reduction is highest. This can pose a risk as tropical corals become stressed when Ω falls below 3, especially in combination with other stressors, such as marine heat waves. At high latitudes, the aragonite saturation state is naturally lower and acidification drives some areas to become undersaturated with respect to aragonite, creating corrosive conditions for aragonite shells.
Control Variables
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Genetic Diversity
Maximum extinction rate compatible with preserving the genetic basis of the biosphere's ecological complexity
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Functional Integrity
Human appropriation of net primary productivity (HANPP) as a percentage of net primary production (NPP)
Drivers
Introduction on invasive species
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Harvesting and burning of biomass
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Data
Global human appropriation of net primary production in the last century
from Kastner et al. 2021 [https://doi.org/10.1111/gcb.15932]
Cumulative (1500-2022) extinctions compared to baseline
from Ceballosa and Ehrlich (2023) [https://www.pnas.org/doi/epdf/10.1073/pnas.2306987120]
Cumulative genera extinctions over time
from Ceballosa and Ehrlich (2023) [https://www.pnas.org/doi/epdf/10.1073/pnas.2306987120]
Connected Tipping Points
If the status of this Planetary Boundary continues to deteriorate, it will push many tipping elements toward tipping, including:
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The death of warm-water coral reefs
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Deoxygenation of marine environments
Drivers & Interconnections
Human activity is the central contributor to breaching the Planetary Boundaries. Our actions almost always affect the planet in many ways. We need to take a holistic view, considering a whole earth approach to the decisions that we take.
Find out more about tipping points
The most viable areas for positive transformation are in energy generation, land use and consumption of resources. All can have substantial, positive effects on maintaining our safe operating space for humanity.
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