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A changing climate means a changing ocean. While the full impacts of climate change on the oceans are unclear, studies predict increasing temperatures, rising sea levels and changes to the ocean chemistry, such as ocean acidification, among others.
The ocean and coasts provide critical ecosystem services such as carbon storage, oxygen generation, food and income generation.
As the ocean absorbs carbon dioxide (CO2) released into the atmosphere by human activities, the carbonate chemistry and acidity of seawater is modified in a process known as ocean acidification. While this leaves less carbon dioxide in the atmosphere and substantially limits climate change, ocean acidification, which is sometimes referred to as the “other CO2 problem”, has emerged as a key global issue in the last decade because of its potential to affect marine organisms and biogeochemical cycles. (1)
Coastal ecosystems like mangroves, salt marshes and seagrasses play a vital role in carbon storage and sequestration. Per unit of area, they sequester carbon faster and far more efficiently than terrestrial forests. When these ecosystems are degraded, lost or converted, massive amounts of CO2 – an estimated 0.15-1.02 billion tons every year – are released into the atmosphere or ocean, accounting for up to 19% of global carbon emissions from deforestation. The ecosystem services such as flood and storm protection that they provide are also lost. (2)
The impacts of ocean warming and acidification on coastal and marine species and ecosystems are already observable. For example, the current amount of CO2 in the atmosphere is already too high for coral reefs to thrive, putting at risk food provision, flood protection and other services corals provide. Moreover, increased GHG emissions exacerbate the impact of already existing stressors on coastal and marine environments from land-based activities (e.g. urban discharges, agricultural runoff and plastic waste) and the ongoing, unsustainable exploitation of these systems (e.g. overfishing, deep-sea mining and coastal development). These cumulative impacts weaken the ability of the ocean and coasts to continue to perform critical ecosystem services. (2)
The degradation of coastal and marine ecosystems threatens the physical, economic and food security of coastal communities – around 40% of the world population. Local fishers, indigenous and other coastal communities, international business organisations and the tourism industry are already seeing the effects of climate change particularly in Small Island Developing States and many of the Least Developed Countries (2).
Weakened or even lost ecosystems increase human vulnerability in the face of climate change and undermine the ability of countries to implement climate change adaptation and disaster risk reduction measures.
- Oceans and climate change, IAEA 2019
- The ocean and climate change, IUCN Global, NOVEMBER 2017