Not necessary. The loss in biomass in fish[0][1] and insects[2][3] and tropical rainforests[4] can account for that. Birds have also taken a deep dive[6]. The most visible I think it is for fish. There alone we've lost an approximate 80% since the 1950ies. Imagine that. 80% of fish biomass, just gone. Similar for insects. German nature reserves have seen a decline of insect population by 75%. Really; non-livestock mammalian biomass is the least of our problems.

> Not really. Even desalination is cheap enough at this point (on the order of 1kL/$, last I checked) that we’d be fine with modest cost increases.

That only covers populations near bodies of water. Ironically these are the most vulnerable to climate change and threatened by the rising sea level. And while it might be possible to build and maintain the desalination infrastructure for the 9M people in Israel, good look trying the same thing in countries like India[8] or Balgladesh[8a]?

Water crises have been ranked in the top five of the World Economic Forum's Global Risks by Impact list nearly every year since 2012[9].

A quarter of the world's population faces severe water shortage[10]. Are you going to provide water to 3 Billion people using desalination plants? In many of these places, even water treatment plants are too expensive to operate. What are you going to power these plants with? Coal? We don't even have a plan to migrate the already existing energy infrastructure to renewables.

> What exactly are you predicting here? This sounds very apocalyptic but doesn’t match any plausible model I’m aware of for ecological failure modes

Here's a helpful link[11].

The norther African coast of the Mediterranean used to be woodland. The continued depletion and over exploitation of the has led to it being the arid region it is today [12]. Now imagine that, but on a global scale. Because the last 250 years have been harsh for our ecosystem and it's now as threadbare as it can be. Ecosystem fragmentation is already a dire issue. The strings in the web are breaking, one by one [13].

[0] https://www.aaas.org/news/researcher-reports-stunning-losses...

[1] https://www.researchgate.net/publication/266684781_A_century...

[2] https://journals.plos.org/plosone/article?id=10.1371/journal...

[3] https://en.wikipedia.org/wiki/Decline_in_insect_populations

[4] https://www.researchgate.net/publication/326657472_Loss_of_b...

[5] https://www.sciencedaily.com/releases/2021/02/210225082525.h...

[6] https://abcbirds.org/wp-content/uploads/2019/10/Bird-Decline...

[7] https://www.researchgate.net/publication/309200743_Defaunati...

[8] https://qz.com/india/1114843/chinas-grand-plan-for-the-brahm...

[8a] https://undark.org/2021/08/04/the-water-crisis-in-climate-vu...

[9] http://www3.weforum.org/docs/WEF_The_Global_Risks_Report_202...

[10] https://news.trust.org/item/20200902202142-ku0o2

[11] https://en.wikipedia.org/wiki/Ecological_collapse

[12] https://en.wikipedia.org/wiki/Deforestation_during_the_Roman...

[13] https://theecologist.org/2012/feb/27/humanity-has-already-ha...

No non-trivial total biomass change occurs on scales shorter than thousands of years

"The biomass is the mass of living biological organisms in a given area or ecosystem at a given time."

Of course fish and insects are part of the biomass.

This paper tries to measure the thing you claimed as 75% over the last hundred or so years as actually being around 45% over the last 5,000 years. http://vaclavsmil.com/wp-content/uploads/PDR37-4.Smil_.pgs61... I found this on the greenpeace website, so if anything this is probably a gross overestimate.

Let's assume good faith on both sides, otherwise this discussion will go nowhere. Agreed?

> They’re not the total biomass

No, they're not. I never claimed that. My claim was that

>> Of course fish and insects are part of the biomass.

Anyway. That out of the way, let's have a look at

> Just because a couple species types have declined by X%,

It's not a couple of species. It's whole ecosystems that are being emptied. The Zoological Society of London report [0] monitors 4392 vertebrate species. There's a consistent and dramatic reduction.

> This paper tries to measure the thing you claimed

Thanks for the research and for taking it serious enough to do some data hunting. I'll happily dig into the report. Since it's from 2011, I wonder if there's an updated version that includes more recent data.

I honestly don't have a better source that aggregates the loss globally over all species. I would be interested in more exact numbers. (Ask HN?!)

>>>> but at least might not be off by orders of magnitude.

I think we have established that the 75% is not "off by orders of magnitude". Could it be 60% reduction? Or 50%? Sure. Absent more data this could be possible, certainly. Given that it's only been a few decades, I don't think that matter too much - it's devastating in any case.

But I think we can agree that it's definitively above 7.5% or 0.75%. I honestly think that 75% is not too far off.

[0] https://www.zsl.org/sites/default/files/LPR%202020%20Full%20...

It’s hard to assume good faith when you keep saying nonsense and then acting like you didn’t. You said:

> Since the middle of the 20th century, we've lost about 75% of biomass and roundabout the same in biodiversity.

That’s obviously untrue, so now you’re acting like you were only talking about fish?

> I think we have established that the 75% is not "off by orders of magnitude". Could it be 60% reduction? Or 50%? Sure.

Did you notice that the 45% reduction was over five thousand years, not ~75 years as you claimed?

Once again, you are saying totally whack stuff to the point where I have to assume you are trolling me somehow.

> That’s obviously untrue,

I've provided quite a bit of material for your research. Here are some highlights:

- birds: reduced by 29% (north america) since 1970

- birds: reduced by 20% (europe) since 1980

- ocean fishes: 80% lost in the last 100 years (global)

- insects: 82% lost in the last 27 years (Europe)

- freshwater fishes: 80% lost since 1970

- non-livestock mammals: 78% lost since 1960

I freely admit that the 75% since 1950 number is a ballpark guess. Given the data I refer to above, I reckon it's not far off. Certainly not orders of magnitude and it is certainly not "obviously untrue". We can debate if we lost 75% or 65% or 55%, but given the consequences in any case it doesn't really matter[0].

> so now you’re acting like you were only talking about fish?

What? No. I'm talking about global, total biomass. Every species, every habitat. I'm sorry if that wasn't clear. (Why would you think that I was talking only about fish? Are you trolling me?)

With regards to fish I wrote

> The most visible I think it is for fish. There alone we've lost an approximate 80% since the 1950ies.

To rephrase; the decline of fish is easily observed by the ever diminishing returns of fishery fleets and there's a lot of data about development of the fish population.

> Did you notice that the 45% reduction was over five thousand years, not ~75 years as you claimed?

That's one paper that makes some assumptions and comes up with a model. I have to check it in detail and it looks interesting. But that does not in any way refute the data in the papers I already provided or the very comprehensive report by ZSL[1]. This is a very thorough study that compiles data for 21,000 populations of animals from 4392 species.

To quote: "The population sizes of mammals, birds, fish, amphibians and reptiles have seen an alarming average drop of 68% since 1970.

> Once again, you are saying totally whack stuff to the point where I have to assume you are trolling me somehow.

I'm sorry if you got that impression, because it's not my intention. I thought that I'd made a good case by quoting the research and various papers. I'm not sure why you say that this is "totally whack"; everything is sourced pretty well.

[0] We're staring into the abyss and the abyss is winking back.

[1] https://www.zsl.org/sites/default/files/LPR%202020%20Full%20...