Author of The Consuming Geographies of Food Newport, Shropshire, UK
Without agriculture, as a hunter-gatherer species, we would (like any other animal) breed up to the limit the land could support and then suffer culls by starvation and disease to maintain this level.
Fertile land, like most of Europe, might support one hunter-gatherer per 26 square kilometers, but this falls to as low as one per 250 km2 in the Australian desert, as calculated by Ian Simmons in his book Changing the Face of the Earth.
The World Bank estimates that 37 per cent of Earth can be classed as agricultural land, but through forest clearance, agriculture has probably been responsible for some degradation and desertification of formerly fertile lands. So let’s say that, in a pre-scientific age, 50 per cent of Earth’s 500-million-km2 land area (minus Antarctica) would be “fertile”. Using Simmons’s figures, we then have a non-agricultural population of around 10 million people.
Sutton Coldfield, West Midlands, UK
The short answer is about 10 million. Growing crops increases the population that can be sustained by the same area of land. This is why the earliest civilisations developed alongside major rivers, where the water could also be used to irrigate the ground. This led to a population explosion to maybe 50 million people, concentrated in Mesopotamia, ancient Egypt and the Indus valley.
Agriculture has increased the proportion of biomass that is edible. This has been enhanced by the use of insecticides, herbicides and artificial fertiliser. Yields have also been enhanced by plant and animal breeding, and factory farms increase them still further. The land available for farming has been expanded by irrigating deserts and draining swamps.
But the population increase to nearly 8 billion wouldn’t have been possible without the economic systems and transport infrastructure that allows food to be moved from place to place.
Imagine if they were uninvented and we had to draw lots to decide who would inhabit this new agriculture world. Each of us would have odds of about 1 in 800. Given that we are bending nature to our will to extract 800 times as much food as it would yield naturally, we surely have a responsibility not to waste what we produce.
Guildford, Surrey, UK
The most likely answer is something between 2 million and 20 million, as without agriculture, we would be restricted to a semi-nomadic lifestyle.
What is certain is that in such a world, with no domesticated livestock, there would be millions more elephants and hundreds of thousands more lions, tigers and whales. This would be fantastic. However, it is most likely that we would be reading about it in New Scientist.
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