Surfing The Sixth Wave

Guest Post by Willis Eschenbach

I keep reading about how we’re already well into the “Sixth Wave Of Extinctions”­. Now, I’ve studied this question extensively. I started back in 2010 with a post called “Where Are The Corpses“, in which I looked at the IUCN Red List of Threatened Species and found that contrary to the “Sixth Wave” hype, 95% of mammal and bird extinctions occurred on islands and in Australia, where they were due to humans introducing new “alien” species after millennia of isolation.

Craig Loehle got in touch with me and proposed that we turn it into a paper for the journals. He did the writing and I did the numbers, because I feel like I have to give myself a lobotomy to write in the dense boring style favored by the journals. He did an excellent job and shepherded it through the publication process, for which he has my eternal gratitude. It’s published in Diversity and Distributions as “Historical bird and terrestrial mammal extinction rates and causes“, and it’s gotten over 150 citations in the journals.

But of course, the alarmism continued. Folks said things like ‘But Willis, you only looked at mammals and birds. The Living Planet Index says there’s been a 70% reduction in the numbers of vertebrate species since 1970’.

Now, I’ve spent a good chunk of my life working outdoors, and I live in the forest and watch the local wildlife. That claim set my bad number detector ringing like the school lunch bell. I researched it and a few weeks ago I wrote another analysis called “E Pur Si Muove“, in which I showed that the LPI claims were strongly contradicted by the Red List data.

But the claims continued. This time it’s ‘But Willis, the LPI only shows fish, mammals, birds, reptiles, and amphibians. What about all the rest of life.’

As Michael Corleone said, “Just when I thought I was out, they pull me back in!”. So, once more into the breach, dear friends …

Let me start with some numbers from the IUCN Red List. It’s the official list of threatened, non-threatened, and extinct members of four great kingdoms of life—animals, plants, fungi, and chromista. And what are chromista when they’re at home? I asked that myself. Turns out they’re a group of mostly single-celled and also some larger life forms that include diatoms, mildews, and sea kelp.

The Red List has data on some 157,190 species of all kinds in all habitats around the planet. I do love it that the first two on the list are the “Black Emo Skink” and the “Viper Moray” … great band names for 2024. Gotta love our most mysterious planet. Here are Red List results.

Figure 1. Red List results showing the number of species that they have analyzed.

Of these 157,190 species, 909 species are listed as extinct, with the earliest extinctions happening in the 1400s. The graph below shows the count of extinct and extant species.

Figure 2. All extinct and extant species with data in the Red List

Mmmm … gotta say, I’m not seeing the “Sixth Wave Of Extinctions”.

Moving on, I find claims like these:

“Drastically increased rates of species extinctions … are well documented.”

and

“Nature is declining globally at rates unprecedented in human history – and the rate of species extinctions is accelerating.”

So I thought I’d look at extinction rates over time to see if “the rate of species extinctions is accelerating”.

Now, as my studies have indicated, a disproportionate number of extinctions occurred on islands and Australia when melanin-deficient folks first stumbled upon them and introduced new, alien species. (I’m told by the usually reliable sources that it’s not politically correct to say “melanin-deficient”. According to the best authorities, the proper term to use is “melanin-challenged”, so all the white folks don’t get triggered by being called “deficient” … but I digress.)

However, these island species are only a small percentage of the total number of species—as you’d expect, there are far, far more species on the giant continents and in the ocean than on the small islands. And there are no more undiscovered islands to face the full onslaught of introduced species. However, the islands contain a large percentage of all extinctions.

So setting those extinctions aside for the moment, here is the history of all of the continental and marine Red List extinctions for which the Red List has a date for the extinction. The early data is sparse and as a result, contains few extinctions per year, so I’ve shown the period 1850-on when far more extinctions were occurring per year, and for which we have much better data.

Figure 3. All extinctions of continental and marine species, 1850 to Jan 2024. These are grouped into 5-year bins. The red line is the trend from 1850 to 2000 rather than to the present, to avoid distorting the trend because it can take a couple of decades for an extinction to be verified.

And to close the circle, here’s the same analysis including all of the known extinctions which have a date for the extinction.

Figure 4. All known extinctions of all species, 1850 to Jan 2024. Details as in Figure 3. Note that with the inclusion of island extinctions, the average extinction rate is double that of Figure 3.

As you can see, there’s been no significant trend in the rate of extinctions over the last 150 years, either just including the continental and marine species, or including all species.

Now, is the post-1850 rate of extinctions greater than the geological rate? Absolutely. It’s an order of magnitude or so greater.

But is it a “Sixth Wave Of Extinctions”?

Let’s consider it this way. The 1850-2000 average is 3.6 extinctions of continental and marine species per year, with a peak value of about 8 extinctions per year. The Red List contains 157,190 continental and marine species, of which 909 are extinct.

So if the rate of extinctions continues at the current level, by the year 2100 we’d see an additional 3.6 extinctions/year * 76 years = 274 extinctions.

But heck, let’s get radical—let’s use ten times that current extinction rate, or 36 extinctions per year. It’s extremely unlikely, it’s never happened in the Red List record, but for this analysis, let’s use that extinction rate to be very conservative on the safe side.

That would give us 3,645 total extinctions by the year 2100. Here’s how that would look, shown to the same scale as Figure 2.

Sorry, friends, but I gotta say that even if extinctions increased to an unbelievable ten times the current extinction rate, I’m still not seeing the fabled “Sixth Wave Of Extinctions”

Now, does this mean we shouldn’t care about extinctions?

Absolutely not. We need to be aware of all of the results of our human actions, and wherever possible and practical, make allowances for the creatures that we share the planet with. I worked a good chunk of my life as a commercial fisherman. I’d love for my two-year-old grandson to be able to do the same … and the only way to do that is to be sensitive to our effects on the ocean.

However, we also need to maintain a sense of proportion. Extinctions are a part of how nature works. Fun fact: ~99.9% of all species that ever existed have gone extinct.

And if some given species, after millions of years of evolution, only exists in a tiny area of the planet, its odds of extinction are very high no matter what we do. It obviously cannot adapt to even the smallest change in its surroundings—if it could, it would be found in a far larger range. Here’s a Red List description of one such extinct species:

“Stypodon signifer [Stumptooth Minnow]: This species is only known from 6 specimens collected in 1880 and 1903, so its biology is mostly unknown. It occurred in springs on the floor of the Parras Valley [in Guanajuato, Mexico].”

Sorry to be so blunt, but that joker is one of nature’s losers circling the drain. And fighting to prevent its extinction would have been a waste of time.

TL;DR Version? The “Sixth Wave” ain’t waving, so if someone starts telling you about the “Sixth Wave Of Extinctions”, feel free to laugh and refer them to this analysis.

w.

My Usual: When you comment, please quote the exact words you’re discussing. It avoids endless misunderstandings.