Thread by @BjornLomborg

Everyone heard Australia's fires killed billions of animals

But we weren't told this happens every year

Rough estimates show 2019-20 was actually one of the least deadly fires in 120 years.

Last century: 16 billion animals harmed each year
2000s: 9 billion
2019-20: 6 billion

As discussed below, this rough estimate uses the same, but simplified, calculations as the original 1 (and later 3) billion claim

Original total number killed/harmed: vertebrates/ha*area burned

As reptiles make up 87% of all harmed, and Australia average is 200/ha:

WWF found 3 billion, because only counted in "uncharacteristic" burn areas

But surely a burned animal matter equally whether its fire is covered on TV or not?

Burning elsewhere was *much* lower, hence many fewer harmed there (we ought to know that, too)

wwf.org.au/ArticleDocumen…

The original 1 billion estimate was from Professor Dickman, who focused on NSW and then some more

sydney.edu.au/news-opinion/n…

The "billion animals dead in Australia's fires" meme got extraordinary coverage

An irresistibly simple measure of "OMG-bad"

leading to the wrong conclusion

vox.com/future-perfect…
abcnews.go.com/International/…
people.com/pets/australia…
smithsonianmag.com/smart-news/mor…
straitstimes.com/asia/australia…

The 1 billion estimate was explicitly based on the 2007 WWF report "Impacts of Land Clearing"

sydney.edu.au/news-opinion/n…
researchgate.net/publication/31…

Report uses similar approach (vertebrates/ha*area burned) and finds about 80% of all dead are reptiles

It starts with Australia average of 200 reptiles/ha, and says number higher in large areas of desert land, so smaller in NSW at 129.5/ha (25.9*5, p30)
researchgate.net/publication/31…

The final 3 billion report uses a lot more careful modeling of population density

Clearly 61K killed/harmed koalas of 260K population is terrible

But overarching main message is "3 billion", of which 87% are reptiles

wwf.org.au/ArticleDocumen…

For reptiles, researchers use lots of specific estimates for population density and find 2.46 billion killed/harmed

They also show that the simple 200/ha gives a very similar but slightly more conservative estimate of 2.29 billion (7% lower)

If you want to estimate the number of animals killed/harmed from Australian fire, you can't just pick favorite fires

I use *all* burned area

Australia-wide all-species number can conservatively be estimated using just reptiles, since they constitute vast majority of all dead

2019-20 was unusual in that it had *much more* fire in eucalyptus forests and much less fire in Grass and Woodland

— more fire where WWF estimated dead, much less where they didn't

https://twitter.com/BjornLomborg/status/1368550021818421249

Here, I'm using the Australian average of 200 reptiles/ha

This is likely very conservative for central Australia, which prof Dickman says is "reptile-rich"

And we know that species density is much higher, and likely also population density
…ublish-csiro-au.stanford.idm.oclc.org/book/7845/

3 billion killed/harmed story relies on counting animals only in TV-covered fires

Estimated across all fires in 2019-20, likely 6.1 billion vertebrates were killed/harmed

An approximation, but unlikely to change qualitative result (size of 2019-20 compared to other years)

You were told a story of 3 billion killed/harmed animals

And without context, it was easy to stun you and make you assume this was worst-ever

You were told that it was "unprecedented" and one of the "worst wildlife disasters in modern history"

but no

wwf.org.au/ArticleDocumen…

Because fires in non-counted areas were *much* lower than usual, the total vertebrate killed/harmed in 2019-20 was actually one of the lowest in the last 120 years

Context matters for making good decisions

Fire data, with links here

https://twitter.com/BjornLomborg/status/1368550005787787270

More context: Is 6.1 billion mostly dead reptiles a lot?

Each year, Australia's 2 million feral cats kill 2 billion reptiles publish.csiro.au/wr/WR17160

Each year, 30+ billion reptiles die of all causes (library.museum.wa.gov.au/fullRecord.jsp…) of a population of 154 billion

The largest documented fire in Australia in 1974-75, at 117 million ha, likely killed 23 billion reptiles (117m ha*200/ha)

p44 from amazon.com/Burning-Bush-F…