Paul Ehrlich. His 1968 book, The Population Bomb, warned that by the end of the 20th century, humanity would face a population explosion followed by a sudden, devastating collapse.
According to the UN, the percentage of the population which is “undernourished” has fallen from 33 per cent to 16 since 1968. Global food production has easily kept pace with population: again, thanks to advances in agricultural technology, specifically those which drove the so-called Green Revolution. Through aggressive use of selective breeding and agricultural chemicals, and the development of new breeds of wheat and rice, what seemed to be looming disaster was averted. Rice yields per hectare in Asia tripled, and food costs plummeted. The "father of the Green Revolution", an American agronomist and plant geneticist called Norman Borlaug, won the Nobel Peace Prize. He was described as the "Forgotten benefactor of mankind" by Atlantic Monthly, and credited having prevented a billion deaths.
That Malthus and Ehrlich were both so wrong is a tribute to human ingenuity. It’s also a warning to those who try to forecast the future. Neither of them predicted the revolutions in food production. Neither did they foresee another, even simpler, change in human behaviour: a global drop in fertility. The average woman now has just 2.52 children – down from 4.85 when Ehrlich was writing. In Europe and the United States, that has dropped to 1.53 and 2.07 respectively. This is thanks to contraception, to greater urbanisation and economic development, and to the education of women.
Farm yields have been marching upwards for decades and will continue to do so. In the past sixty years, the total harvest of the big three crops that provide the bulk of our calories - maize, wheat and rice - has tripled, yet the acreage planted has hardly changed.
This trend is going to continue partly thanks to low-tech changes already in the pipeline. Helped by Chinese investment, improved transport to get African crops to market with less waste will make a big difference. As will tractors, which boost production by 25% or so - because they free the land for human food that would otherwise be needed to feed bullocks or horses.
African farmers will start to use much more fertilizer, as western farmers do, which makes it possible to sustain yields without exhausting the soil. A few years ago environmentalists argued that fertiliser would soon run short, because it is made using natural gas, a fossil fuel. But the discovery of how to extract abundant shale gas has turned that argument on its head: there are probably many decades' worth of natural gas now available to make fertilizer.
There are high-tech changes afoot too. Maize and rice that have been genetically modified to resist pests and use less water, soybeans with better amino acid balance for pig food, wheat that can resist rust - all these are coming. Benighted Europe may reject these GM crops for superstitious reasons but surely not for long. The environmental benefits alone are now stark: GM crops can be pest resistant without the use of sprays that kill harmless insect bystanders.
The more yields increase, the more land can be set aside from food production for reforestation and national parks. This is happening already. National parks are expanding steadily, and land that was once farmed is being returned to forest, especially in countries like Britain and America. That is a huge contrast to a century ago, when farming kept up with population only by expanding into new areas of steppe, pampas and prairie.
Don't forget another factor. Carbon dioxide levels in the air are rising. CO2 is a raw material that plants use to make sugars, which is why many greenhouse owners pump CO2 over their crops to boost production. The results of more than 600 experiments with rice, wheat and soybeans exposed to the sort of carbon dioxide levels expected by 2050 (an extra 300 parts per million) all show remarkably consistent 30+% increases in yield. And the higher the CO2, the less water a plant loses in absorbing it, so water stress will improve too. Plus, if global warming happens, it is likely to produce more rainfall, so that regions like the Sahel will continue to become greener, as it has in recent decades.
For all these reasons food production will probably continue to rise faster than population in the decades ahead. There will still be price spikes caused by bad weather or foolish policies, and there will be challenges: policies that encourage innovation cannot be taken for granted. Yet so long as trade is free and innovation flourishes, by 2050 it is easily possible that we can feed nine billion people with more and better food from less land.
I don't see an issue with feeding livestock or people anytime soon. Population isn't a problem and food production isn't an issue.