GLOBAL WARMING: COWS OR CARS? - MEAT: A Benign Extravagance - page 202

that can subsequently be used for cropping. 30 You can take the animals out of these systems
but a proportion of the nitrogen is necessary for human food production, whether or not it
passes through the gut of an animal.
On top of this, since animal products supply a third of all the world's protein, if we elim-
inated livestock, we would have to produce half as much again of vegetable protein crops
to replace the meat foregone (though less if we only aimed to replace the energy in the meat
forgone). 31 This means that we would still need to apply the nitrogen fertilizer that we had
previously been spreading on feed crops onto replacement food crops; and we would need
to continue to produce leguminous crops such as soya beans for human consumption.
And in addition to all of this, animal faeces are not going to disappear from the face of
the earth if we stop keeping domestic animals. Figures in Livestock's Long Shadow suggest
that currently three tonnes of volatile nitrogen are produced by wild animals for every 23
tonnes produced by domestic animals. 32 It seems more than likely that if humans stopped
grazing livestock, then the population of wild animals would increase. Many might regard
this as a good thing, but it would eat into the N 2 O emissions savings, though probably not
enormously.
In short, many of these nitrous oxide emissions are a consequence not of livestock, but
of an agricultural ecology in which livestock plays an incidental role, transmitting rather
than creating nitrogen. That is why the World Resources Institute chart (see Fig 3 ), for ex-
ample, only classes a small fraction of its nitrous emissions under 'Livestock and Manure',
and places the majority of them under the heading 'Agricultural Soils'.
Perhaps it would be possible to work out what would be the net savings in N 2 O emis-
sions if we dispensed with livestock and made global agriculture stock free - but I am not
going to do anything more than hazard a broad guess. To summarize, if we went stock free,
(a) we would still need at least the area currently devoted to feed crops for our own nourishment;
(b) we would need to substitute synthetic nitrogen or green manures for perhaps two thirds of the manure we
currently use;
(c) there would be a small, perhaps negligible, amount of increased emissions from wild animals.
Taking this into account, together with the fact that the IPCC have recently lowered some
of the default emission factors, I suspect that the net N 2 O emissions from meat might only
be around half as high as those given by the FAO.
Methane
Similar issues arise when we consider the final third of the FAO's 18 per cent of GHGs
(5.4 per cent to be precise) which consist of methane, mostly emanating from the digest-
ive systems of ruminants. In one sense it is the most crucial of the three greenhouse gases
because it is intrinsic to farm animal metabolism, and less a consequence of the way they