Compared with 100 years ago, the total biomass of predatory fish (basically, the ones we eat) is down by roughly 70%. And that’s accelerating.
Maybe a better question would be: where can I find more information on the consequences of this?
The excellent 2009 documentary "The End of the Line" was the first place I heard discuss catastrophic fish population crashes, and it covers this dramatic topic and its very serious implications in detail. It also talks about the mind-boggling, almost unbelievable scale at which modern fishing vessels such as supertrawlers operate.
Frankly, I was horrified by what I learned about modern fishing watching this movie.
This is a BS statistic meant to shock and inappropriately counts the entire area of wilderness that might be used for grazing which is just wilderness that would have supported similar animals anyway.
Even grazing land rarely looks anything like it does before we've shaped it for our use. And even when it does, at first glance, it gets a monoculture of animals, instead. Farmers are not keen on seeing their herds deal with competition or predation from the wild.
That doesn't seem right. According to the FAO (United Nations), only 1.3 billion hectares of land are arable while nearly 5 billion hectares are used for agriculture. That's more like ~25%. And the latter figure only accounts for 38% of the world's land area, so the earlier half figure claim doesn't seem right either.
I suppose if the margin of error on those approximations is exceptionally large...
0.06 Gt C human biomass
0.1 Gt C livestock biomass
0.007 Gt C wild mammal biomass
0.002 Gt C wild bird biomass
[1]: https://www.pnas.org/doi/10.1073/pnas.1711842115
[2]: https://github.com/milo-lab/biomass_distribution/blob/master...
Most of the worlds land megafauna are gone because big slow things are really easy to kill for groups of primitive humans with pointy sticks.
>In 1800, it was estimated there were forty million bison, by 1883, there were few wild bison in the United States - most were in Yellowstone National Park. By 1900, there were less than a thousand left in North America.
48% of bird species in decline: https://news.cornell.edu/stories/2022/05/global-bird-populat...
among other examples. In 2018 it was estimated by the WWF that 60% of the animal population was lost between 1970 and 2014: https://www.wwf.org.uk/updates/living-planet-report-2018
Some people change their behavior when they learn they their current behaviors are contributing to significant harm and there is a viable alternative to reduce harm.
We've got a choice about whether we contribute to the harm caused by commercial fishing or not.
I don’t eat a lot of fish, and what I do eat is mostly aquacultured here in New Zealand: freshwater salmon and green-lipped mussels are the lowest impact options available to me.
I sometimes have wild-caught fish when I’m away with friends who spearfish. On the very rare occasion I buy wild-caught fish, I’m very picky about species and method (long lines or maybe set netted, never trawled)
A couple decades ago the concept of overfishing became more well-known, and the industry was forced to change. The reason that the industry reacted also has to do with the fact that a true collapse of the fish population would also decimate the entire industry - they have an interest in keeping it stable.
If 99% of a fish population goes away, it would take decades for the population to recover to normal levels. During those years, there would be no profit.
The true reason why the fish population is down 70% is due to the fact that every year the fishing industry takes out as many fish as possible without causing a lasting depression of fish population.
If all fishing would be stopped right now, the global fish population would recover to pre-human levels within probably 20 or 30 years.
Here's what someone from the Australian fishing industriy has to say about this:
"We have learned from the ’60s to ’90s era and today most large fisheries are well managed (some in Asia/Africa are not) and either recovering or operating at maximum economic yield. You cannot catch fish to extinction – they will always recover if you stop fishing. It’s the recovery time that is the issue – and the time to when you can recommence harvesting, sustainably."
Of course these people are heavily biased, and the industry is rotten to the core and full of corruption, but it's hard to argue against this self-evident logic.
It’s not a collapse of “the ocean”, but: https://en.wikipedia.org/wiki/Collapse_of_the_Atlantic_north...
Also, you completely ignore 2nd and 3rd order effects - decimation of populations dependent on those missing fish that can't and won't recover as easily as fish can.
There are some paradoxical concepts in fisheries management, not least is that the Maximum Sustinable Yield often supports aligned interests between fisherman (who want to profit/eat) and fish populations (who want to persist). Overfishing is a tragedy of the commons; managing those fisheries properly can produce MORE fish in the ocean even if yields go up. Not always, but this stuff is not cut and dry and the dynamics of population growth and extraction in these animals have to be understood.
I'll take an example from New Zealand because it's where I live and what I know about. New Zealand has a huge fishery EEZ and is, I believe, widely regarded has having one of the most "well managed" fisheries in the world.
And yet, in large parts of our inland waters a combination of soil runoff and bottom trawling has turned millions of acres of seabed from incredibly productive nurseries of seagrass beds and shellfish-covered rocky reefs... into featureless swathes of sediment called "Kina barrens" (basically, dominated by a kind of spiky sea-urchin). These areas have passed a tipping point, there's basically no getting them back. Shellfish can't attach to the mucky sediment to regenerate the reefs or filter the water, and seagrass is instantly eaten by the sea-urchins, which run amok because there's no nursery for the snapper population that would normally keep them in check.
I don't know what my point is, really, other than to say that I think it's hubris to think we have a sophisticated enough understanding of ecosystems to balance thousands of species on the knife-edge of fishing them to maximum sustainable pressure. Sometimes we'll get it wrong and an ecosystem will go "pop". Then we can't get it back.
As for positive prescriptions -- The main thing I've heard is that we should be urgently pushing for marine reserves. And that they absolutely have to be large and NO-TAKE. The goal should be something wildly optimistic like 50% of EEZs. Fishing can happen in the other half. (For reference here's where we currently are: https://www.researchgate.net/figure/Map-of-no-take-areas-and... )
"It's basic school knowledge that any population will recover, as long as you have a couple organisms left who can reproduce and the environment itself hasn't fundamentally changed."
I just recently took a biology class, and that is fundamentally not the case. One of the major causes of population collapse leading to extinction is lack of genetic diversity once a population is small. Once diversity is too low, even if conditions are relatively favorable, a population is much more vulnerable to disease or seemingly small changes to the environment. One of the ways biologists try to "rescue" populations these days is by introducing genetic diversity where possible.