Oceans and Fisheries

It’s hard to imagine, but even the seeming vastness of our oceans is under the same threat as the forests. Our oceans are dying.

  1. Empty oceans – overfishing
  2. Acidic oceans – the evil twin of climate change
  3. Hotter oceans
  4. Plastic oceans

1. Empty Oceans – Overfishing

It’s predicted that if overfishing continues at the current pace, all the world’s fisheries will collapse by the year 2048.

Eighty percent of global fisheries are already considered fully exploited or over-exploited…
The Nature Conservancy

Fishing provides 14-16% of humanity’s animal protein, and over 1 billion people rely on it as their primary source of protein. But we risk permanently damaging fisheries when we over-fish.

According to a 2008 UN report, the world’s fishing fleets are losing US$50 billion each year due to depleted stocks and poor fisheries management. The report, produced jointly by the World Bank and the UN Food and Agriculture Organization (FAO), asserts that half the world’s fishing fleet could be scrapped with no change in catch. In addition, the biomass of global fish stocks have been allowed to run down to the point where it is no longer possible to catch the amount of fish that could be caught.[28] Increased incidence of schistosomiasis in Africa has been linked to declines of fish species that eat the snails carrying the disease-causing parasites.[29] Massive growth of jellyfish populations threaten fish stocks, as they compete with fish for food, eat fish eggs, and poison or swarm fish, and can survive in oxygen depleted environments where fish cannot; they wreak massive havoc on commercial fisheries. Overfishing eliminates a major jellyfish competitor and predator, exacerbating the jellyfish population explosion.[30] Both climate change and a restructuring of the ecosystem have been found to be major roles in an increase in jellyfish population in the Irish Sea in the 1990s.[31]

According to the 2019 Global Assessment Report on Biodiversity and Ecosystem Services published by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, overfishing is a primary driver of mass extinction in the world’s oceans.[32] A 2021 study published in the journal Nature asserted that the “primary cause” of ocean defaunation is overfishing.[24]

Overfishing – wikipedia September 2021

We are simply harvesting too many fish too fast. They don’t have the time or resources to regrow. We are also fishing inefficiently. Bottom trawling is a perverse method of fishing that scrapes the sea-floor of all life, only to sell a tiny fraction of the actual catch. The majority is just considered collateral damage. Most of the catch is then thrown back into the sea as ‘by-catch’. It also destroys important sponge ecosystems along the bottom of our oceans.

Bottom Trawling

National Geographic photographer Brian Skerry on bottom trawling (TED 2010). His work is beautiful, but the subject is not. As Brian’s TED talk so graphically shows, a mere handful of 7 or 8 shrimp kills 10 pounds of ‘by-catch’.

2. Acidic oceans — the evil twin of climate change

TED Talk: 9 minutes — June 2017

Triona McGrath reports that 70% of our reefs could be gone by 2100 – and the reefs represent a full quarter of the total ocean’s biodiversity! That’s over 17% of all life in the ocean gone – just because the oceans are getting too acidic. Not overfishing, not over-heating, and not plastics. Just acidity!

The Smithsonian puts it this way:-

Ocean acidification is sometimes called “climate change’s equally evil twin,” and for good reason: it’s a significant and harmful consequence of excess carbon dioxide in the atmosphere that we don’t see or feel because its effects are happening underwater. At least one-quarter of the carbon dioxide (CO2) released by burning coal, oil and gas doesn’t stay in the air, but instead dissolves into the ocean. Since the beginning of the industrial era, the ocean has absorbed some 525 billion tons of CO2 from the atmosphere, presently around 22 million tons per day.

At first, scientists thought that this might be a good thing because it leaves less carbon dioxide in the air to warm the planet. But in the past decade, they’ve realized that this slowed warming has come at the cost of changing the ocean’s chemistry. When carbon dioxide dissolves in seawater, the water becomes more acidic and the ocean’s pH (a measure of how acidic or basic the ocean is) drops. Even though the ocean is immense, enough carbon dioxide can have a major impact. In the past 200 years alone, ocean water has become 30 percent more acidic—faster than any known change in ocean chemistry in the last 50 million years…

…Overall, it’s expected to have dramatic and mostly negative impacts on ocean ecosystems—although some species (especially those that live in estuaries) are finding ways to adapt to the changing conditions.

The Smithsonian has a comprehensive page

Not only this, but if pushed too far, questions have been raised about whether ocean acidity will enter a feedback loop as the acid dissolves shelled creatures that release their CO2 to increase acidity – where previously they would have die and sunk to the ocean floor to eventually become limestone.

3. Hotter oceans

Jeremy Jackson explains the manifold issues of overfishing, acidifying and over-heating the oceans. He starts talking about climate change and warmer oceans about 12 minutes in, but the first part of the talk covers other themes on this page really well.

4. Plastic oceans

Everyone has seen photos of dead birds or whales with their stomachs cut open and copious piles of plastic trash spewing out. But what many do not realise is that plastics, even microplastics, absorb heavy metals and toxins from the ocean and these bioaccumulate up the ocean food chain.

Oceana – under 5 minutes


Not only that, but micro and nano-plastics are everywhere in our environment – and as this European Food Safety Authority (2021 – 3 minutes) youtube shows, scientists have barely begun to calibrate how they detect and quantify microplastics and their effects on human health. Contact me if you learn more.

For a more comprehensive read, see the Smithsonian again

Where does all this plastic go? Surprisingly – models show how a majority seems to float within 100km of our coastlines and then get washed back onto our shores where it bashes about a bit. This degrades the plastic and makes it micro-plastic.

The fact that a majority stays within 100km means beach clean-up days are extremely important as they are actually tackling the very heart of the pollution problem. It’s where most of the plastic is and it will stop it weathering down to microplastics. It also means these ocean bins are another important tool.