Month: January 2024

Guest Post by Willis Eschenbach

A few years back, some scientists got together and invented something they call the Living Planet Index, or LPI. It’s supposed to measure how well (or poorly) the species that make up the living world are doing. They say it is a “measure of the state of the world’s biological diversity based on population trends of vertebrate species.” So it’s an index based on the decline of some selected species, which is claimed to represent the decline of the species of the “living world”.

Here’s the big news from their latest report.

The Living Planet Index claims an average 70% decline in the populations of species worldwide since 1970.

YIKES! 70% loss since 1970! EVERYONE PANIC!

But is this true?

Over in the Twitterverse where I’m @weschenbach, I said that based solely on my experience, their claim was nonsense. I’ve spent a lot of the last half-century outdoors in the elements, both on land and on and under the sea, around the planet. I said I would have noticed a 70% reduction in species populations.

Of course, folks who spend their lives behind desks in a city thought I was being ridiculous, and they laughed uproariously. How could I be so certain? Plus of course, there were the claims of “But Willis, those are actual scientists! How can you doubt them?”

So I thought I’d take a look at some real data. Let’s get a sense of the number of the species involved.

There are estimated to be around 8.7 million species on earth. Of these, about 65,000 are vertebrates.

How many of these 8.7 million species are studied by the Living Planet Index? Well, not all of them.

First, no plants, no fungi, no chromista. Next, only vertebrates, and only some of those, specifically fish, mammals, birds, reptiles, and amphibians.

The good news is that the IUCN Red List of Threatened Species, which is the official keeper of data on which species are threatened or not, lists data for 62,493 vertebrates, so it covers pretty much all of the vertebrates.

It also allows us to search based on various criteria, including those used by the LPI listed above.

And when we eliminate the vertebrate species the LPI doesn’t include, we end up with 59,866 species fitting the LPI criteria—mammals, birds, reptiles, fish, and amphibians. Of course, they didn’t look at all of them, only 5,230. But I wanted a larger view of the issues.

The Red List also lets us see if the populations of each species are increasing, stable, or decreasing.

Of the populations of the 30,763 of the LPI-studied mammal etc. species for which the Red List has population data, 53% have stable or increasing populations. So we’re left with 14,565 species with decreasing populations. Call it half to be generous.

Here’s the problem. If around half the species for which we have data are stable or increasing, then even if the rest were all totally extinct, the average decline would only be 50% … far from the 70% they claim.

Oooops …

Next, as a sensitivity analysis, let’s assume every one of the 28,714 species for which we don’t have the population trend is decreasing. Clearly, that’s not possible—some will be increasing or stable. And because the Red List is focused on threatened species, the unknown species will likely be weighted towards stable species. But it’s a sensitivity analysis, so we’ll assume every one of the unmeasured species is decreasing.

With that impossible assumption purely for a sensitivity analysis, it would mean only 27% of the species are stable or increasing.

And the problem still remains. With 27% not decreasing, the only way to get to a 70% decrease in population is if almost every one of the 33,861 theoretically decreasing species is already extinct or on the brink of extinction. Only that impossible situation would give us a 70% average decrease.

Conclusions?

Out of 59,866 species fitting the LPI criteria for which we have population data, just over half are stable or increasing.

Of the 59,866 species, only 8,509 are both decreasing and in some trouble (vulnerable or near threatened or endangered or critically endangered). Here’s the Red List Report:

The endangered and decreasing fish, birds, reptiles, amphibians, and mammals are 0.001% of all species, and there’s no reason to assume that their condition reflects the world situation.

The 70% claim of the LPI is falsified by the Red List data.

As I said, I have investigated this because based solely on my experience, I said I didn’t believe the LPI numbers, and folks laughed at that. And now, having studied the species data, I find that my experience is correct—their claims don’t hold water.

So how did the scientists behind the LPI get it so wrong? Obviously, their selected species are not representative of the whole.

I would suggest that Upton Sinclair had the answer to that. He said:

“It is difficult to get a man to understand something, when his salary depends on his not understanding it.”

The problem is, if the LPI was going up, or just slightly downwards, the scientists behind the LPI would be out of a job. To use George Orwell’s term, that’s doubleplusungood …

And almost inevitably, this leads to an unconscious bias in their choice of species, locations, and studies to include in the LPI. For the LPI, they’ve studied 31,821 populations of 5,230 species. So no overt bias is needed—just picking study A over study B because reasons, choosing population 1 over population 2, selecting species Alpha over species Beta, lather, rinse, repeat, and soon you have a 70% decline since 1970.

Finally, please be clear that I’m not saying that we should ignore population decreases. I’ve been a commercial fisherman for a good deal of my life, and I’d like my grandson to be able to do the same. The only way for that to happen is for us to care for the other life forms with which we share this magical planet. I’m just saying that the LPI is just more unsupported alarmism.

Best to all, and yeah, I’ll continue to trust my experience despite people laughing at it … I’m funny that way.

w.

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Related

If you want to know more about an exoplanet atmosphere, watch how it changes over time. That’s the mantra of a group of astronomers who just reported on conditions at Tylos, otherwise known as WASP-121 b.

Tylos is a hot Jupiter world. It lies in a tidally locked 30-hour orbit around WASP-121. That means the planet shows the same face toward its star. As a result, one hemisphere is heated to over 3000 K. Such “overheating” affects the weather on Tylos and creates a hotspot on the star-facing side. That high temperature atmosphere makes for some intriguing chemicals there.

Astronomers wanted to track the heat-driven atmospheric changes, according to Quentin Changeat, principal investigator of a team that used three years’ worth of Hubble data to study Tylos. “Studying exoplanets’ weather is vital to understanding the complexity of exoplanet atmospheres, especially in our search for exoplanets with habitable conditions,” he noted, and compared it to studying Earth’s weather. “Weather on Earth is responsible for many aspects of our life, and in fact, the long-term stability of Earth’s climate and its weather is likely the reason why life could emerge in the first place.”

Hubble’s Exoplanet Atmosphere Advantage

The venerable Hubble Space Telescope continues to amass a pretty remarkable archive of exoplanet observations, including peeks at their atmospheres. That allows astronomers to look at how those worlds and their atmospheres change over time. Hubble has observed Tylos several times, and the datasets give a unique look at how its atmosphere behaves.

Changeat’s team combined four sets of archival observations of Tylos made using Hubble’s Wide Field Camera 3 (WFC 3). The combined data set includes a look at the planet transiting in front of its star in June 2016). There’s also a peek at it transiting behind its star in November 2016). Two phase curves measure the amount of light detected from the planet and its star during an orbit. They were taken in March 2018 and February 2019. The team carefully processed the data, which was a lengthy process.

“Our dataset represents a significant amount of observing time for a single planet and is currently the only consistent set of such repeated observations,” explained Changeat. “The information that we extracted from those observations was used to characterize (infer the chemistry, temperature, and clouds) of the atmosphere of WASP-121 b at different times. This provided us with an exquisite picture of the planet, changing in time.”

About Tylos’s Atmosphere

As the team worked with the datasets, they found that the planet’s hotspot was shifting. In addition, the spectral fingerprint of chemicals indicated that something about the planetary atmosphere was changing. That led the team to create computer models to explain the changes they were seeing. The best explanation so far is that there are quasi-periodic weather patterns at Tylos. They resemble massive cyclones. Over time, they arise, rage across the upper atmosphere, and then dissipate. The huge temperature differences between the hotter and cooler regions likely play a role in these patterns.

This video shows the weather patterns in the exoplanet atmosphere of WASP-121 b, also known as Tylos. This video is slowed down to show the patterns in the exoplanet’s atmosphere in more detail. Courtesy: NASA, ESA, Q. Changeat et al., M. Zamani (ESA/Hubble)

In addition, the behavior of the hot spot on Tylos is especially intriguing. Such hot spots are pretty common. They don’t always stay in the same place but instead seem to migrate slightly through the atmosphere. Astronomers see that “offset” position in many exoplanets. The best explanation for that apparent shift could be the presence of upper atmospheric winds or some other disturbance that affects the stability of a hotspot.

Seeing shifts in a hotspot and changes in weather patterns on a world 880 light-years away is a big accomplishment and marks a big step forward in exoplanet observations. “The high resolution of our exoplanet atmosphere simulations allows us to accurately model the weather on ultra-hot planets like WASP-121 b,” explained Jack Skinner, a postdoctoral fellow at the California Institute of Technology and co-leader of the project. “Here we make a significant step forward by combining observational constraints with atmosphere simulations to understand the time-varying weather on these planets.”

Future Work

Observing exoplanets and their atmospheres isn’t a “one shot and you’re done” kind of activity. Light from the star moves through the atmosphere. As it passes through, specific chemicals absorb various wavelengths of light. A spectral study of that light shows “dropouts” where the absorptions happen and those dropouts tell scientists what chemicals exist there. It can also indicate changes in the atmospheric chemistry over time.

A NASA graphic explaining how a telescope can measure an exoplanet atmosphere using spectroscopy. Courtesy: NASA/JPL-Caltech/Lizbeth B. De La Torre.

As this study indicates, “temporal resolution” (i.e. many observations over a longer period) gives astronomers more chances to understand how these worlds change. The additional data are added to models that explain atmospheric evolution. We’ve learned that in studies of our gas giants, for example. Neptune and Uranus showed tantalizing storms in the snapshots taken by the Voyager 2 spacecraft decades ago. Follow-up observations over longer periods from Hubble and the Keck II telescopes (for example), allow planetary scientists to track storms and other atmospheric disturbances. The same is true for studies of Mars and its surface markings. Temporal resolution is a valuable tool.

So, applying the same approach to distant exoplanets will, in the long run, give us insights into changes in their atmospheres. And, it will eventually show us which ones may have life onboard, simply from the evidence of certain chemicals in their blankets of air. Long-term observations by Hubble and, of course, the JWST, will give more evidence of weather patterns on distant worlds. Eventually, they’ll turn up those worlds that can support life, and their atmospheric studies may well tell us what that life is like, how long it’s been there, and what effect it has on its home world.

For More Information

Hubble Observes a Changing Exoplanet Atmosphere
Is the Atmosphere of the Ultra-hot Jupiter WASP-121b Variable?

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