Agriculture Reference
In-Depth Information
after is a 'land-take ratio' telling us, for example, that a hectare will produce x times as
much human nourishment when put down to corn as it will when given over to livestock.
A further problem is that different commentators, for no obvious reason other than their
ideological allegiance, regularly come up with different figures. Almost every item of lit-
erature on the environmental impact of meat cites a typical feed conversion ratio, or else
a range, but the ratio given can be anything from 1:1 to 20:1. Anyone who dares to re-
search the matter further finds themselves facing a mass of confiicting statistics, incom-
patible units, shifting variables and ill-defined terms. Understandably, popular writers and
members of the public like to alight on one safe, handy figure for assessing the extravag-
ance of a meat diet in comparison to a vegan diet, and frequently they veer towards the
ratio of 10:1.
The earliest (and most elegantly expressed) use of the ten-to-one figure I have located is
in Shelley's
A Vindication of Natural Diet
where he observes:
The quantity of nutritious vegetable matter consumed in fattening the carcase of
an ox, would afford ten times the sustenance … if gathered immediately from the bos-
om of the earth.
4
Here for example is an early modern statement, in respect of protein, from Peter Singer:
Assume we have one acre of fertile land. We can use this acre to grow a high-pro-
tein plant food, like peas or beans. If we do this, we will get between 300 and 500
lbs of protein from our acre. Alternatively we can use our acre to grow a crop that we
feed to animals, and then kill and eat the animals. Then we will end up with between
40 and 55 lbs of protein … Most estimates conclude that plant foods yield about ten
times as much protein per acre as meat does.
5
The attraction of this rule of thumb, irrespective of which units of measurement and
methodology are employed, is so marked that I have made a collection of examples, a num-
ber of which are given in the panels overleaf, to demonstrate the variety of approaches that
can be taken.
Although common, use of the 10:1 formula is by no means universal. Many writers take
pains to provide a range of conversion ratios specific to different species of animal, or in
order to distinguish between protein content and energy content. The trouble is that differ-
ent writers come up with different figures, which are often a reflection of their ideological
position.
For example Marvin Harris, a pro-carnivore anthropologist, writes: 'it takes four grams
