World’s fisheries slowly suffocating due to climate change

By 2080, the vast majority of the planet’s oceans will suffer from a lack of oxygen, with potentially devastating consequences for marine ecosystems.

A new study conducted by the American Geophysical Union, first published in the organisation’s journal, Geophysical Research Letters, is the first of its kind to use climate modelling to predict how, when and where de-oxygenation will take place in seas, beyond naturally-occurring variability. 

The research found that within the next 60 years, 70% of the ocean will have undergone this process, threatening all aquatic animals, which rely on oxygen in water to survive. Moreover, the middle depths, or mesopelagic zones, which are found between 200 and 1000 metres deep, will be the first areas to lose significant amounts of oxygen. Crucially, this is the habitat of many of the world’s commercially-fished species, raising the spectre of food shortages, economic hardship and the collapse of an entire industry.

‘This zone is actually very important to us because a lot of commercial fish live in this zone,’ said Yuntao Zhou, an oceanographer at Shanghai Jiao Tong University and lead study author. ‘Deoxygenation affects other marine resources as well, but fisheries [are] maybe most related to our daily life.’

Oceans closer to the poles, for example the west and north Pacific, are particularly vulnerable to de-oxygenation, which is caused by rising temperatures, with warmer water able to store less O2. In contrast, the tropics are home to so-called oxygen minimum zones, which are now believed to be spreading to cover much larger areas. 

‘The oxygen minimum zones actually are spreading into high latitude areas, both to the north and the south. That’s something we need to pay more attention to,’ she says, highlighting that even if global warming goes into reverse, allowing for more dissolved oxygen to be stored in ocean and sea water, there is no clear evidence oxygen could return to pre-industrialised levels. 

In related news, last week Environment Journal reported on how just 15% of the world’s coastal regions remain intact. Meanwhile, a separate investigation has suggested even if global temperatures peak at 1.5C above pre-industrial levels, which they are expected to hit by 2040, the impact on coral reef systems will be ‘catastrophic‘. 

Image credit: Paul Einerhand