Chemistry Reference
In-Depth Information
analyses have reached similar conclusions that in order to avoid severe
degradation of the natural capital offered by soils, and to reduce GHG
emissions, future systems for crop production will need to produce higher
yields on existing cropland, limit expansion of the cultivated area, achieve a
substantial increase in N fertiliser efficiency, and improve soil quality through
increasing soil organic matter.
80,82
An influential and wide-ranging assessment of future food and farming
concluded that sustainable intensification was required to meet future
demands for food, and that all technological means of achieving this should
be assessed and appropriately utilised.
79
How best to achieve this intensifica-
tion, and whether intensification will lead to land being spared for other
ecological services, is a subject of considerable current debate and research.
The extent to which past increases of crop yields have spared land for nature
conservation is a matter of considerable debate because: (i) the on-farm losses
of biodiversity due to practices giving high yields may outweigh the benefits of
sparing biodiverse habitats; (ii) high-yielding crops may have negative effects
on off-site biodiversity; and (iii) land-sparing does not occur or is imperfect.
The complexity of the factors involved is indicated in an analysis of the
changes in yields of 23 staple crops for 124 countries between 1979 and 1999.
83
While the per capita area of the 23 staple crops decreased in developing
countries where large yield increases occurred, this was countered by a
tendency for an increased area of non-staple crops, leading to only a weak
tendency for land-sparing overall. In developed countries there was no
evidence that higher yields reduced per capita cropped areas, probably because
agricultural subsidies promoted production, thereby overriding any land-
sparing effects. The study concluded that land-sparing is a weak process, but
that improved agricultural technology may have contributed to the main-
tenance of natural vegetation cover in the past and that future conservation
benefits, while debatable, are potentially available if land-use policies are also
modified.
83
The potential of different routes to achieving intensification to meet future
food demands is a topic of on-going research, but several studies have
indicated the importance of approaches that combine multiple disciplines that
take account of local soil, ecological and societal conditions.
84,85
For example,
alternative pathways to increasing yields to the required levels were
investigated in one global study involving technological and educational
advances.
86
The options examined were: (i) current technology, in which each
economic group retained its present relation between yield and N fertiliser use;
(ii) technological improvement, in which technological advances continue
along existing temporal trends to 2050; (iii) technology transfer, in which low-
yielding countries adopt and adapt the existing high-yielding technologies of
high-yielding countries; and (iv) technology improvement and transfer, in
which all countries achieve soil- and climate- adjusted yields. If present trends
of intensification in rich nations and extensification in poor nations persist,
then
d
n
1
r
2
n
g
|
1
d
n
6
h
3
by 2050
an
additional
1 billion
ha
of
land
would be
cleared and
