Paying for the environmental damage they do would render global industries unprofitable overnight
The externalities are massive.
Grist's David Roberts reports on a paper produced by environmental consultancy Trucost, which assess the value of the externalities used by the world's industries, and comes to an astonishing conclusion:
Of the top 20 region-sectors ranked by environmental impacts, none would be profitable if environmental costs were fully integrated. Ponder that for a moment. None of the world’s top industrial sectors would be profitable if they were paying their full freight. None!
Backtracking a bit. An externality is a cost or benefit of production which is not internalised into the cost of production. If I use electricity to make widgets, I have to pay for it; but if I "use" the atmosphere to make widgets, by releasing pollution into it, then I don't have to pay a dime.
What that means is that the standard logic of the free market – that voluntary transactions will always make everyone better off – breaks down. If I make £1 profit from each widget I produce, but cause £2 of damage to the environment, then my incentive is to keep pumping out widgets, even though there's a net loss of £1 to the world for every one I make.
The standard economic response to this problem is to call for externalities to be "priced in". If I have to pay the £2 damage that my pollution causes, I won't make widgets until I clean up the production process.
That is the logic behind calls for a carbon tax, but it actually applies to a lot of environmental problems. The Trucost paper looks at water use, land use, air pollution, land and water pollution, and waste as well as just greenhouse gas emissions, and puts a cost on each of them. And when it does, it finds that a lot of industries might not be profitable if they had to pay the full cost of what they do:
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Coal power generation in Eastern Asia, which generates revenues of $443.1bn, has a natural capital cost of $452.8bn (that's unpriced natural capital – the report already takes into account the various ways in which industries are forced to price in their externalities), largely due to greenhouse gases. Cattle ranching in South America, with revenues of $16.6bn, has capital cost of $353.8bn, due to the unpriced cost of land use. And so on.
You can quibble the figures – and doubtless many will – but what is clear is they are large. Really, really large. Many of the biggest industries in the world can only exist because they don't have to pay the true environmental cost of what they do. The word "unsustainable" is thrown around too much these days, but it seems to fit here.