Oxygen in the world’s oceans is depleting at an unprecedented rate, leaving species gasping for breath and devastating marine habitats, a report issued at the annual UN climate talks in Madrid has warned.
The International Union for Conservation of Nature (ICUN) study by 67 scientists from 17 countries found oxygen levels in oceans declined by about 2 per cent between 1960 and 2010.
The deoxygenation is largely attributed to climate disruption, though other human activities are contributing to the problem, notably nutrient run-off, when too many nutrients from fertilisers used on farms and lawns wash into waterways.
Large fish species are at particular risk, the study warns, with many vital ecosystems in danger of collapse. Dead zones – where oxygen is effectively absent – have quadrupled in the past half-century, and there are also at least 700 areas where oxygen is at dangerously low levels.
ICUN acting director general Grethel Aguilar said the health of oceans should be a key consideration for the talks. "As the warming ocean loses oxygen, the delicate balance of marine life is thrown into disarray. The potentially dire effects on fisheries and vulnerable coastal communities mean that the decisions made at the conference are even more crucial."
The problem is being compounded because the world’s oceans are already being overfished, and assailed by a rising tide of plastics, as well as other pollutants.
"A healthy ocean with abundant wildlife is capable of slowing the rate of climate breakdown substantially," said Dr Monica Verbeek, director of Seas at Risk. "Ending overfishing is a quick, deliverable action which will restore fish populations, create more resilient ocean ecosystems, decrease CO2 pollution and increase carbon capture, and deliver more profitable fisheries and thriving coastal communities."
UN special envoy for the oceans Peter Thomson, speaking during Oceans Action Day on Saturday, said the latest evidence supported the view of UN secretary general António Guterres that "humanity is knowingly destroying the planetary support system".
A series of major international gatherings on oceans, biodiversity loss and COP26 would make 2020 the critical year to “get it right for the next decade” in reversing declines. “If we get that wrong, we might as well put up the surrender flag,” he added.
The COP25 talks are going into their second week seeking to finalise a rulebook on implementing the Paris Agreement from January 1st.
Though many details were agreed last year at COP24, fractious negotiations failed to satisfy some countries, especially Brazil, on how far carbon credits for forestry would be permitted as offsets for greenhouse gas emissions.
This has continued to provide an obstacle to progress over the first week of COP25, according to Irish climatologist Prof John Sweeney, a veteran attender of the annual talks. Countries such as Brazil, India and China want to be able to carry over a huge number of unused credits gained in former years.
“This would allow them continued large scale increases emissions and severely compromise achievement of the Paris objective of limiting global warming to 1.5 degrees above pre-industrial levels...there is a real risk that ‘creative accounting’ will allow double counting of emission reductions to enable a compromise of sorts to be achieved,” he told The Irish Times.
He added: “The next few days will be crucial in seeking to prevent this. Indeed the focus on the carbon market has increasingly turned the COP into a commercial ‘circus’ and taken the focus off where it should be – major reductions in emissions.”
"One might be forgiven for thinking the global manifestation of concern for where we are headed in the climate change emergency would have encouraged negotiators to forgo national self interest in favour of what Pope Francis calls 'Our Common Home'."
But there was little evidence thus far of this, he said. "The arrival of Greta Thunberg and a strong representation of young people from around the world has done little to soften 'hard bitten' negotiators who beaver away behind closed doors with little external interaction with the rest of participants. Their priorities are not the global priorities. Rather it is 'what's good for my country first and foremost'."
It was not a recent phenomenon, nor could it be blamed on the rise of populism and demagogic leaders. “Rather the roots run deeper into how political systems protect self-interest and vested interests and employ public servants to resist compromises even where they are in the long-term benefit of their population,” Prof Sweeney added.
“Unless dramatic leadership is displayed this week when the political leaders arrive, COP25 is not going to make a dent in the rising curve of global emissions,” he predicted, “and the five wasted years since Paris are likely to be continue, much to the detriment of present and future generations facing climate dislocation on a growing scale.”
The organisers of a protest on Friday claimed 500,000 people marched through Madrid to demand more urgency to address global warming in what was the largest climate rally ever staged in Europe
“The change we need is not going to come from people in power,” Ms Thunberg told the crowds.
“The change is going to come from the people, the masses, demanding change.”