Well, We're Killing the Atmosphere but We Can Do Better. How About the Oceans?

We usually think of climate change as what happens to us on dry land. Heatwaves, droughts, floods, severe storm events, that sort of thing. We rarely think that most of the impacts of global warming are swallowed up by the seas that comprise 70 per cent of the Earth's surface.

The oceans take most of the heat (you would be frying without them) and they absorb most of the carbon from the atmosphere. But why not hit them when they're down? I know, let's strip the oxygen right out of them. Fish, who needs 'em?

Oxygen in the oceans is being lost at an unprecedented rate, with “dead zones” proliferating and hundreds more areas showing oxygen dangerously depleted, as a result of the climate emergency and intensive farming, experts have warned. 

Sharks, tuna, marlin and other large fish species were at particular risk, scientists said, with many vital ecosystems in danger of collapse. Dead zones – where oxygen is effectively absent – have quadrupled in extent in the last half-century, and there are also at least 700 areas where oxygen is at dangerously low levels, up from 45 when research was undertaken in the 1960s. 

The International Union for the Conservation of Nature presented the findings on Saturday at the UN climate conference in Madrid, where governments are halfway through tense negotiations aimed at tackling the climate crisis.

Farmers often tell us that they're stewards of the land. Land maybe but not the water. That's where they dispose of their excess agricultural chemicals - the fertilizers, the herbicides, the pesticides. That's the blue-green algae blooms that now poison Lake Winnipeg, Lake Erie and many other rivers and lakes. It's the massive dead zone in the Gulf that pours out of the mighty Mississippi.

Some ocean areas are naturally lower in oxygen than others, but these are even more susceptible to damage when their oxygen levels are depleted further, the report’s authors said. Species that can more easily tolerate low oxygen levels, such as jellyfish, some squid and marine microbes, can flourish at the expense of fish, upsetting the balance of ecosystems. The natural oceanic cycles of phosphorus and nitrogen are also at risk. 

The world’s oceans are already being overfished, and assailed by a rising tide of plastic waste, as well as other pollutants. Seas are about 26% more acidic than in pre-industrial times because of absorbing the excess carbon dioxide in the atmosphere, according to the Intergovernmental Panel on Climate Change, with damaging impacts on shellfish in particular. 

Low oxygen levels are also associated with global heating, because the warmer water holds less oxygen and the heating causes stratification, so there is less of the vital mixing of oxygen-rich and oxygen-poor layers. Oceans are expected to lose about 3-4% of their oxygen by the end of this century, but the impact will be much greater in the levels closest to the surface, where many species are concentrated, and in the mid to high latitudes. 

Intensive farming also plays a major role. When excess artificial fertiliser from crops, or manure from the meat industry, runs off the land and into rivers and seas, it feeds algae which bloom and then cause oxygen depletion as they decompose.

When we speak of a climate emergency it's invariably in the context of greenhouse gases and atmospheric warming. We don't include the environmental devastation we inflict on our lakes and rivers and oceans. We go on about desertification and the degradation of our farmlands while ignoring that the main source of protein for the world's poorest 70 per cent is fish. And, what we don't kill off with our aquatic emissions we ravage with our industrial fishing fleets. That's already playing out in all sorts of ways?

Those Somali pirates who seize freighters off the Horn of Africa? They used to be fishermen - until the giant fishing fleets moved in. We took their sustenance. Says who? I heard that from the mouth of a Danish frigate captain on an anti-piracy patrol.  He had a hard time condemning those pirates.