There is less and less oxygen in the oceans, and that's a problem
Environment — di Andrea Barolini
A report presented at Cop 25 shows how climate change is also causing a reduction in oxygen levels in the oceans. And that's a problem.
There is less and less oxygen in the oceans, and that's a problem
A report presented at Cop 25 shows how climate change is also causing a reduction in oxygen levels in the oceans. And that's a problem.
The oceans risk finding themselves suffocated. Added to the list of the main threats weighing on the world's seas — alongside acidification and unsustainable fishing — is the lack of oxygen caused by global warming. This is explained in a report by the International Union for Conservation of Nature (Iucn), published during the proceedings of Cop 25, the twenty-fifth United Nations world climate conference.
"The delicate balance of marine life has been altered"
67 experts worked on the study, presenting it as the most important document in existence on the subject to date. The text explains how oxygen loss in the oceans represents a growing threat to fishing and to certain animal species, for example in the case of tuna and sharks.
"As the amount of oxygen falls through the warming of water – Grethel Aguilar, Director General of the Iucn, stressed – the delicate balance of marine life is altered. To limit the loss of oxygen in the oceans, as well as the other dramatic effects of climate change, leaders around the world must commit to reducing greenhouse gas emissions immediately and substantially".
Why is the #Ocean losing #Oxygen? 😷 This decrease is threatening marine life and our own food security 🐟. Our expert @KIsensee explains the impacts of deoxygenation on marine ecosystems as described in the latest report by IOC and #iucn. #COP25 #climatechange #saveourocean
In technical terms, oxygen loss is mainly due to two phenomena. The first is linked to the proliferation of certain plant species, starting with algae, caused by the discharge of nutrients from the land and the deposition of nitrogen associated with the use of fossil fuels. The second is linked to the rise in water temperatures.
Oxygen in the oceans down 2 per cent between 1960 and 2010
The result is that globally – the Iucn report specifies – the level of oxygen in the oceans fell by 2 per cent between 1960 and 2010. Projections point to a possible further decline of 3–4 per cent by the end of the century, if emissions continue to grow at the current rate. The study also highlights that "most of this loss is concentrated in the first hundred metres of the water column, where the majority of living species are found".
“To curb ocean oxygen loss alongside the other disastrous impacts of climate change, world leaders must commit to immediate and substantial emission cuts."
Dr Grethel Aguilar, IUCN Acting Director General
Read our new report on ocean deoxygenation ow.ly/p0L350xtz3Q #COP25
Dr Grethel Aguilar, IUCN Acting Director General
Read our new report on ocean deoxygenation ow.ly/p0L350xtz3Q #COP25
The document also explains that there are approximately 700 sites worldwide where oxygen levels are too low. In 1960 there were just 45. Over the same period, the number of completely oxygen-free zones has quadrupled. This favours species that tolerate hypoxia (microbes, jellyfish and some squid) over those that suffer from it most (such as the majority of fish). But the Iucn also highlights the serious consequences that oxygen depletion in the oceans can have on marine mammals, corals and mangroves. All of this has direct repercussions on the populations living in coastal areas as well.