The Royal Society Report - Push-Pull

As diets change, so demand for different types of food will
shift radically, with large numbers of people going through
a ‘nutrition transition’. Increasing urbanisation and growing
prosperity mean that people are more likely to adopt new
diets, particularly consuming more meat, fats and refined
cereals, and fewer traditional cereals, vegetables and fruit
(Fitzhugh 1998; Popkin 1998; Delgado et al. 1999; Smil
2000a). Livestock production has increased dramatically,
with a worldwide 4.4-fold increase in numbers of chickens
since 1961 (to 17 billion), a 2.4-fold increase in pigs (to 9.9
billion), an 0.4–0.5-fold increase in numbers of cattle and
buffalos (to 1.59 billion) and sheep and goats (to
1.96 billion) (see Figure 1.9) (Pretty 2008; FAOSTAT 2009).
Some suggest that demand for livestock products will
double by 2050. Already more than one-third of the world’s
grain is fed to domestic livestock (rising to nearly 70% in
industrialised countries). As incomes rise in developing
countries, so it is expected that demand for meat will tend
towards the per capita consumption rates of 115 kg per
year in the USA and 80 kg per year in the UK. Chinese per
capita annual consumption has already increased from 4 to
54 kg in the past 50 years. On the current trajectory,
livestock production will move further from extensive
(pasture-based grazing) to intensive systems, placing even
more demand on staple grains.
The natural environment can be seen as providing a
set of benefits to agriculture (ecosystem services and
organisms for biological control) and constraints (soil,
water, climate, pests and diseases) that determine what
can be grown, where, when and how. The primary
constraints on crop production are well understood.
These include biophysical factors such as radiant energy
for photosynthesis (dependent on latitude), temperature
(dependent on latitude and altitude), water, plant nutrients
(primarily nitrogen, phosphorus and potassium), pests
(vertebrates and invertebrates), diseases (bacteria, viruses
and fungi), weeds (other plants) and the availability of
suitable land. These constraints are the subject of Chapter
2 of this report.
The effects of climate change on world agriculture are
uncertain. Working Group 2 of the Intergovernmental Panel
on Climate Change (IPCC) has estimated that global crop
production will be threatened by global temperature
increases of 1°C and begin to decline significantly at 3°C
(Easterling et al. 2007). But this global picture flattens out
regional variations that might bring catastrophic impacts
on, for example, the drier tropical areas (Schmidhuber &
Tubiello 2007). The social and economic consequences of
environmental change (including changes to biodiversity
and climate) will exacerbate the uncertainties faced by the
world’s poorest billion people.
1.4 The need for sustainable intensification
Land used for crop production has grown only slightly
over the period 1961 to 2007 (total agricultural area has
expanded 11% from 4.51 to 4.93 billion ha, and arable area
9% from 1.27 to 1.41 billion ha) (FAOSTAT 2009). Over the
same period the human population grew from 3 to
6.7 billion (an increase of 123%). In industrialised countries,
agricultural area has fallen by 3% over the same period,
but has risen by 21% in developing countries. Half of the
1.4 billion ha of land used for arable crop production
produces grain (approximately 700 million ha). In 1960 the
area used to produce grain was 648 million ha.
Improvements to agricultural production are complicated
by a number of pressures on land availability. As cities
grow, they encroach on rural environments and often on
high quality agricultural land (Montgomery 2007). The loss
of soil globally is an increasingly serious problem (Fitter
2005). In many places, land that has previously grown food
is being turned over to biofuels (Royal Society 2008a). In
some countries use of land for food is prohibited by
Figure 1.9. Head of livestock (1961–2007).
5.0
Head of livestock, world (1961–2007) (FAO, 2009)
4.5
4.0
Ratio (1961 = 1)
3.5
3.0
2.5
2.0
Cattle and buffaloes (1961 = 1.03 bn)
Pigs (1961 = 0.46 bn)
Chickens (1961 = 3.89 bn)
Sheep and goats (1961 = 1.34 bn)
1.5
1.0
0.5
1960 1970 1980 1990 2000 2010
6 I October 2009 I Reaping the Benefits The Royal Society