On extinction this [1] is an extremely informative article on how estimations are made, and why they vary in such extreme ways. Observed extinctions are many orders of magnitude less than 6 per hour. The article (2015) references a total of about 800 observed extinctions in 400 years. And some number of those extinctions were not actually extinctions.
So where do the big numbers come from? Obviously we don't know about every animal in existence, so it's safe to say if we have observed 800 extinctions, then many more than that have actually happened. But how many more? And there is no good answer. The most extreme numbers come from taking a sample of one thing you know (e.g. land snails), looking at the extinction ratio there of known_extinct:known_nonextinct land snails, and then extrapolating that to an estimate of the entire number of species on the entire planet. And you end up with a really big number.
Of course if your estimate of species counts is off, if somehow land snails aren't a representative sample of all species, or any other countless factors turn up to be off - then you have problems, easily on the order of many magnitudes. You end up trying to solve a problem with no idea if you're having any effect at all. In the best case scenario, everything works - and you notice no change since the species you are affecting are almost entirely ones we don't even know exist. In the worst case scenario, we've turned into Don Quixote.
In other words, those estimates are as reliable as Drake's equation output. Someone who can't say "I don't know" when they know they don't know, is either a fool or a con artist.
It’s not just that the critical bit for the 800 number is: “That’s because the criteria adopted by the IUCN and others for declaring species extinct are very stringent, requiring targeted research. It’s also because we often simply don’t know what is happening beyond the world of vertebrate animals that make up perhaps 1 percent of known species.”
A great number of species have been described by finding a tiny number of members in a small geographic area. For many of them we just don’t know if they are still around or not and nobody is funding research to check.
well if we're taking into account microorganisms, every mall parking lot ever paved has likely caused the extinction of at least some endemic microorganisms
So where do the big numbers come from? Obviously we don't know about every animal in existence, so it's safe to say if we have observed 800 extinctions, then many more than that have actually happened. But how many more? And there is no good answer. The most extreme numbers come from taking a sample of one thing you know (e.g. land snails), looking at the extinction ratio there of known_extinct:known_nonextinct land snails, and then extrapolating that to an estimate of the entire number of species on the entire planet. And you end up with a really big number.
Of course if your estimate of species counts is off, if somehow land snails aren't a representative sample of all species, or any other countless factors turn up to be off - then you have problems, easily on the order of many magnitudes. You end up trying to solve a problem with no idea if you're having any effect at all. In the best case scenario, everything works - and you notice no change since the species you are affecting are almost entirely ones we don't even know exist. In the worst case scenario, we've turned into Don Quixote.
[1] - https://e360.yale.edu/features/global_extinction_rates_why_d...