One rather surprising outcome is that we have all seen how exponential growth takes a small number, and increases it slowly and then VERY quickly. Many of us will have heard the story of the grains of rice and the chess board, but there’s nothing like first-hand experience to appreciate how quickly a manageable situation can become a crisis. A good approximation of exponential growth is that, if the rate of increase is x%, the time taken for the amount to double is 72/x. With the coronavirus the doubling rate was at one point about 3 days – implying a growth rate of about 24% per day – which is pretty fast. But other things in our lives also grow exponentially – GDP, for instance. According to the World Bank, the average annual growth in world GDP between 1961 and 2018 was a shade under 3.5% – so if that was sustained (and more about sustainability later!) the world’s economy would double in just over 20 years. As we now know, that means the economy would be 4 times the current size after 40 years, 8 times after 60 years, 16 times after 80 years and an astonishing 32 times after 100 years. Now if we thought a doubling in size meant a doubling in resource use, that would clearly be disastrous, but there is some evidence that the resource-intensity of the economy reduces as it grows – because people start paying for yoga lessons and concert tickets, rather than houses and cars. But we haven’t yet seen an example of economic growth without any increase at all in resource use, and we can’t seem to maintain our current standard of life without catastrophic damage to the environment, so what hope is there that we or the rest of the planet could survive a 32-fold increase in economic activity?